diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
index 15aa7c4..075de03 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
@@ -20,13 +20,13 @@
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.mapreduce.Job;
 
-import edu.uci.ics.pregelix.api.graph.GlobalAggregator;
 import edu.uci.ics.pregelix.api.graph.MessageCombiner;
 import edu.uci.ics.pregelix.api.graph.NormalizedKeyComputer;
 import edu.uci.ics.pregelix.api.graph.Vertex;
 import edu.uci.ics.pregelix.api.graph.VertexPartitioner;
 import edu.uci.ics.pregelix.api.io.VertexInputFormat;
 import edu.uci.ics.pregelix.api.io.VertexOutputFormat;
+import edu.uci.ics.pregelix.api.util.GlobalCountAggregator;
 
 /**
  * This class represents a Pregelix job.
@@ -80,6 +80,8 @@
     public static final String RECOVERY_COUNT = "pregelix.recoveryCount";
     /** the checkpoint interval */
     public static final String CKP_INTERVAL = "pregelix.ckpinterval";
+    /** comma */
+    public static final String COMMA_STR = ",";
 
     /**
      * Construct a Pregelix job from an existing configuration
@@ -89,6 +91,7 @@
      */
     public PregelixJob(Configuration conf) throws IOException {
         super(conf);
+        this.addGlobalAggregatorClass(GlobalCountAggregator.class);
     }
 
     /**
@@ -100,6 +103,7 @@
      */
     public PregelixJob(String jobName) throws IOException {
         super(new Configuration(), jobName);
+        this.addGlobalAggregatorClass(GlobalCountAggregator.class);
     }
 
     /**
@@ -113,6 +117,7 @@
      */
     public PregelixJob(Configuration conf, String jobName) throws IOException {
         super(conf, jobName);
+        this.addGlobalAggregatorClass(GlobalCountAggregator.class);
     }
 
     /**
@@ -161,8 +166,10 @@
      * @param globalAggregatorClass
      *            Determines how messages are globally aggregated
      */
-    final public void setGlobalAggregatorClass(Class<?> globalAggregatorClass) {
-        getConfiguration().setClass(GLOBAL_AGGREGATOR_CLASS, globalAggregatorClass, GlobalAggregator.class);
+    final public void addGlobalAggregatorClass(Class<?> globalAggregatorClass) {
+        String aggStr = globalAggregatorClass.getName();
+        String classes = getConfiguration().get(GLOBAL_AGGREGATOR_CLASS);
+        conf.set(GLOBAL_AGGREGATOR_CLASS, classes == null ? aggStr : classes + COMMA_STR + aggStr);
     }
 
     /**
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
index e79d4d2..a5d9cd7 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
@@ -15,6 +15,9 @@
 
 package edu.uci.ics.pregelix.api.util;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.io.WritableComparable;
@@ -117,10 +120,19 @@
      * @return User's vertex combiner class
      */
     @SuppressWarnings({ "rawtypes", "unchecked" })
-    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> Class<? extends GlobalAggregator<I, V, E, M, P, F>> getGlobalAggregatorClass(
+    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> List<Class<? extends GlobalAggregator<I, V, E, M, P, F>>> getGlobalAggregatorClasses(
             Configuration conf) {
-        return (Class<? extends GlobalAggregator<I, V, E, M, P, F>>) conf.getClass(PregelixJob.GLOBAL_AGGREGATOR_CLASS,
-                GlobalCountAggregator.class, GlobalAggregator.class);
+        String aggStrs = conf.get(PregelixJob.GLOBAL_AGGREGATOR_CLASS);
+        String[] classnames = aggStrs.split(PregelixJob.COMMA_STR);
+        try {
+            List<Class<? extends GlobalAggregator<I, V, E, M, P, F>>> classes = new ArrayList<Class<? extends GlobalAggregator<I, V, E, M, P, F>>>();
+            for (int i = 0; i < classnames.length; i++) {
+                classes.add((Class<? extends GlobalAggregator<I, V, E, M, P, F>>) conf.getClassByName(classnames[i]));
+            }
+            return classes;
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException(e);
+        }
     }
 
     public static String getJobId(Configuration conf) {
@@ -161,10 +173,52 @@
      * @return Instantiated user vertex combiner class
      */
     @SuppressWarnings("rawtypes")
-    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> GlobalAggregator<I, V, E, M, P, F> createGlobalAggregator(
+    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> List<GlobalAggregator> createGlobalAggregators(
             Configuration conf) {
-        Class<? extends GlobalAggregator<I, V, E, M, P, F>> globalAggregatorClass = getGlobalAggregatorClass(conf);
-        return ReflectionUtils.newInstance(globalAggregatorClass, conf);
+        List<Class<? extends GlobalAggregator<I, V, E, M, P, F>>> globalAggregatorClasses = getGlobalAggregatorClasses(conf);
+        List<GlobalAggregator> aggs = new ArrayList<GlobalAggregator>();
+        for (Class<? extends GlobalAggregator<I, V, E, M, P, F>> globalAggClass : globalAggregatorClasses) {
+            aggs.add(ReflectionUtils.newInstance(globalAggClass, conf));
+        }
+        return aggs;
+    }
+
+    /**
+     * Get global aggregator class names
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return An array of Global aggregator names
+     */
+    @SuppressWarnings("rawtypes")
+    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> String[] getGlobalAggregatorClassNames(
+            Configuration conf) {
+        List<Class<? extends GlobalAggregator<I, V, E, M, P, F>>> globalAggregatorClasses = getGlobalAggregatorClasses(conf);
+        String[] aggClassNames = new String[globalAggregatorClasses.size()];
+        int i = 0;
+        for (Class<? extends GlobalAggregator<I, V, E, M, P, F>> globalAggClass : globalAggregatorClasses) {
+            aggClassNames[i++] = globalAggClass.getName();
+        }
+        return aggClassNames;
+    }
+
+    /**
+     * Get global aggregator class names
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return An array of Global aggregator names
+     */
+    @SuppressWarnings("rawtypes")
+    public static <I extends WritableComparable, V extends Writable, E extends Writable, M extends WritableSizable, P extends Writable, F extends Writable> String[] getPartialAggregateValueClassNames(
+            Configuration conf) {
+        String[] gloablAggClassNames = getGlobalAggregatorClassNames(conf);
+        String[] partialAggValueClassNames = new String[gloablAggClassNames.length];
+        int i = 0;
+        for (String globalAggClassName : gloablAggClassNames) {
+            partialAggValueClassNames[i++] = getPartialAggregateValueClass(conf, globalAggClassName).getName();
+        }
+        return partialAggValueClassNames;
     }
 
     /**
@@ -306,8 +360,8 @@
      * @return User's global aggregate value class
      */
     @SuppressWarnings("unchecked")
-    public static <M extends Writable> Class<M> getPartialAggregateValueClass(Configuration conf) {
-        return (Class<M>) conf.getClass(PregelixJob.PARTIAL_AGGREGATE_VALUE_CLASS, Writable.class);
+    public static <M extends Writable> Class<M> getPartialAggregateValueClass(Configuration conf, String aggClassName) {
+        return (Class<M>) conf.getClass(PregelixJob.PARTIAL_AGGREGATE_VALUE_CLASS + "$" + aggClassName, Writable.class);
     }
 
     /**
@@ -343,8 +397,8 @@
      * @return User's global aggregate value class
      */
     @SuppressWarnings("unchecked")
-    public static <M extends Writable> Class<M> getFinalAggregateValueClass(Configuration conf) {
-        return (Class<M>) conf.getClass(PregelixJob.FINAL_AGGREGATE_VALUE_CLASS, Writable.class);
+    public static <M extends Writable> Class<M> getFinalAggregateValueClass(Configuration conf, String aggClassName) {
+        return (Class<M>) conf.getClass(PregelixJob.FINAL_AGGREGATE_VALUE_CLASS + "$" + aggClassName, Writable.class);
     }
 
     /**
@@ -372,8 +426,8 @@
      *            Configuration to check
      * @return Instantiated user aggregate value
      */
-    public static <M extends Writable> M createPartialAggregateValue(Configuration conf) {
-        Class<M> aggregateValueClass = getPartialAggregateValueClass(conf);
+    public static <M extends Writable> M createPartialAggregateValue(Configuration conf, String aggClassName) {
+        Class<M> aggregateValueClass = getPartialAggregateValueClass(conf, aggClassName);
         try {
             return aggregateValueClass.newInstance();
         } catch (InstantiationException e) {
@@ -384,6 +438,29 @@
     }
 
     /**
+     * Create the list of user partial aggregate values
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return Instantiated user partial aggregate values
+     */
+    public static <M extends Writable> List<M> createPartialAggregateValues(Configuration conf) {
+        String[] aggClassNames = BspUtils.getGlobalAggregatorClassNames(conf);
+        List<M> aggValueList = new ArrayList<M>();
+        for (String aggClassName : aggClassNames) {
+            Class<M> aggregateValueClass = getPartialAggregateValueClass(conf, aggClassName);
+            try {
+                aggValueList.add(aggregateValueClass.newInstance());
+            } catch (InstantiationException e) {
+                throw new IllegalArgumentException("createAggregateValue: Failed to instantiate", e);
+            } catch (IllegalAccessException e) {
+                throw new IllegalArgumentException("createAggregateValue: Illegally accessed", e);
+            }
+        }
+        return aggValueList;
+    }
+
+    /**
      * Create a user partial combine value
      * 
      * @param conf
@@ -414,8 +491,8 @@
      *            Configuration to check
      * @return Instantiated user aggregate value
      */
-    public static <M extends Writable> M createFinalAggregateValue(Configuration conf) {
-        Class<M> aggregateValueClass = getFinalAggregateValueClass(conf);
+    public static <M extends Writable> M createFinalAggregateValue(Configuration conf, String aggClassName) {
+        Class<M> aggregateValueClass = getFinalAggregateValueClass(conf, aggClassName);
         try {
             return aggregateValueClass.newInstance();
         } catch (InstantiationException e) {
@@ -426,6 +503,29 @@
     }
 
     /**
+     * Create the list of user aggregate values
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return Instantiated user aggregate value
+     */
+    public static <M extends Writable> List<M> createFinalAggregateValues(Configuration conf) {
+        String[] aggClassNames = BspUtils.getGlobalAggregatorClassNames(conf);
+        List<M> aggValueList = new ArrayList<M>();
+        for (String aggClassName : aggClassNames) {
+            Class<M> aggregateValueClass = getFinalAggregateValueClass(conf, aggClassName);
+            try {
+                aggValueList.add(aggregateValueClass.newInstance());
+            } catch (InstantiationException e) {
+                throw new IllegalArgumentException("createAggregateValue: Failed to instantiate", e);
+            } catch (IllegalAccessException e) {
+                throw new IllegalArgumentException("createAggregateValue: Illegally accessed", e);
+            }
+        }
+        return aggValueList;
+    }
+
+    /**
      * Create a user aggregate value
      * 
      * @param conf
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/FrameTupleUtils.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/FrameTupleUtils.java
index a0f67e3..922920e 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/FrameTupleUtils.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/FrameTupleUtils.java
@@ -52,10 +52,12 @@
     public static void flushTupleToHDFS(ArrayTupleBuilder atb, Configuration conf, long superStep)
             throws HyracksDataException {
         try {
-            if (atb.getSize()>0) {
+            if (atb.getSize() > 0) {
                 FileSystem dfs = FileSystem.get(conf);
-                String fileName = BspUtils.getGlobalAggregateSpillingDirName(conf, superStep) +"/" + UUID.randomUUID();
-                FSDataOutputStream dos = dfs.create(new Path(fileName), true);
+                String fileName = BspUtils.getGlobalAggregateSpillingDirName(conf, superStep) + "/" + UUID.randomUUID();
+                Path path = new Path(fileName);
+                FSDataOutputStream dos = dfs.create(path, true);
+                // write the partial aggregate value
                 dos.write(atb.getByteArray(), 0, atb.getSize());
                 dos.flush();
                 dos.close();
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
index 8d9eeac..f703fcc 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
@@ -181,14 +181,18 @@
         conf.setClass(PregelixJob.EDGE_VALUE_CLASS, (Class<?>) edgeValueType, Writable.class);
         conf.setClass(PregelixJob.MESSAGE_VALUE_CLASS, (Class<?>) messageValueType, Writable.class);
 
-        Class aggregatorClass = BspUtils.getGlobalAggregatorClass(conf);
-        if (!aggregatorClass.equals(GlobalAggregator.class)) {
-            List<Type> argTypes = ReflectionUtils.getTypeArguments(GlobalAggregator.class, aggregatorClass);
-            Type partialAggregateValueType = argTypes.get(4);
-            conf.setClass(PregelixJob.PARTIAL_AGGREGATE_VALUE_CLASS, (Class<?>) partialAggregateValueType,
-                    Writable.class);
-            Type finalAggregateValueType = argTypes.get(5);
-            conf.setClass(PregelixJob.FINAL_AGGREGATE_VALUE_CLASS, (Class<?>) finalAggregateValueType, Writable.class);
+        List aggregatorClasses = BspUtils.getGlobalAggregatorClasses(conf);
+        for (int i = 0; i < aggregatorClasses.size(); i++) {
+            Class aggregatorClass = (Class) aggregatorClasses.get(i);
+            if (!aggregatorClass.equals(GlobalAggregator.class)) {
+                List<Type> argTypes = ReflectionUtils.getTypeArguments(GlobalAggregator.class, aggregatorClass);
+                Type partialAggregateValueType = argTypes.get(4);
+                conf.setClass(PregelixJob.PARTIAL_AGGREGATE_VALUE_CLASS + "$" + aggregatorClass.getName(),
+                        (Class<?>) partialAggregateValueType, Writable.class);
+                Type finalAggregateValueType = argTypes.get(5);
+                conf.setClass(PregelixJob.FINAL_AGGREGATE_VALUE_CLASS + "$" + aggregatorClass.getName(),
+                        (Class<?>) finalAggregateValueType, Writable.class);
+            }
         }
 
         Class combinerClass = BspUtils.getMessageCombinerClass(conf);
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
index 9fefbea..1bad401 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
@@ -101,7 +101,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         IConfigurationFactory confFactory = new ConfigurationFactory(conf);
         JobSpecification spec = new JobSpecification();
 
@@ -137,7 +137,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -168,7 +168,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
@@ -305,7 +305,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         JobSpecification spec = new JobSpecification();
 
         /**
@@ -364,7 +364,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -448,7 +448,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
index ee576b1..d01c069 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
@@ -78,7 +78,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         IConfigurationFactory confFactory = new ConfigurationFactory(conf);
         JobSpecification spec = new JobSpecification();
 
@@ -109,7 +109,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -185,7 +185,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
@@ -261,7 +261,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         JobSpecification spec = new JobSpecification();
 
         /**
@@ -313,7 +313,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -382,7 +382,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
index 32271c8..4480b97 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
@@ -78,7 +78,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         IConfigurationFactory confFactory = new ConfigurationFactory(conf);
         JobSpecification spec = new JobSpecification();
 
@@ -112,7 +112,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -179,7 +179,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
@@ -252,7 +252,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         JobSpecification spec = new JobSpecification();
 
         /**
@@ -304,7 +304,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -365,7 +365,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
index 3aa36cd..7ca771c 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
@@ -78,7 +78,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         IConfigurationFactory confFactory = new ConfigurationFactory(conf);
         JobSpecification spec = new JobSpecification();
 
@@ -109,7 +109,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -193,7 +193,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
@@ -266,7 +266,7 @@
         Class<? extends WritableComparable<?>> vertexIdClass = BspUtils.getVertexIndexClass(conf);
         Class<? extends Writable> vertexClass = BspUtils.getVertexClass(conf);
         Class<? extends Writable> messageValueClass = BspUtils.getMessageValueClass(conf);
-        Class<? extends Writable> partialAggregateValueClass = BspUtils.getPartialAggregateValueClass(conf);
+        String[] partialAggregateValueClassNames = BspUtils.getPartialAggregateValueClassNames(conf);
         JobSpecification spec = new JobSpecification();
 
         /**
@@ -318,7 +318,7 @@
         RecordDescriptor rdDummy = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
                 VLongWritable.class.getName());
         RecordDescriptor rdPartialAggregate = DataflowUtils.getRecordDescriptorFromWritableClasses(conf,
-                partialAggregateValueClass.getName());
+                partialAggregateValueClassNames);
         IConfigurationFactory configurationFactory = new ConfigurationFactory(conf);
         IRuntimeHookFactory preHookFactory = new RuntimeHookFactory(configurationFactory);
         IRecordDescriptorFactory inputRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
@@ -395,7 +395,7 @@
          * final aggregate write operator
          */
         IRecordDescriptorFactory aggRdFactory = DataflowUtils.getWritableRecordDescriptorFactoryFromWritableClasses(
-                conf, partialAggregateValueClass.getName());
+                conf, partialAggregateValueClassNames);
         FinalAggregateOperatorDescriptor finalAggregator = new FinalAggregateOperatorDescriptor(spec,
                 configurationFactory, aggRdFactory, jobId);
         PartitionConstraintHelper.addPartitionCountConstraint(spec, finalAggregator, 1);
diff --git a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/FinalAggregateOperatorDescriptor.java b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/FinalAggregateOperatorDescriptor.java
index c0be9dd..d32cb6b 100644
--- a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/FinalAggregateOperatorDescriptor.java
+++ b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/FinalAggregateOperatorDescriptor.java
@@ -19,6 +19,9 @@
 import java.io.DataInputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileStatus;
@@ -58,21 +61,24 @@
     }
 
     @Override
+    @SuppressWarnings("rawtypes")
     public IOperatorNodePushable createPushRuntime(final IHyracksTaskContext ctx,
             IRecordDescriptorProvider recordDescProvider, int partition, int nPartitions) throws HyracksDataException {
         return new AbstractUnaryInputSinkOperatorNodePushable() {
             private Configuration conf = confFactory.createConfiguration(ctx);
-            @SuppressWarnings("rawtypes")
-            private GlobalAggregator aggregator = BspUtils.createGlobalAggregator(conf);
+            private List<GlobalAggregator> aggregators = BspUtils.createGlobalAggregators(conf);
+            private List<String> aggregateClassNames = Arrays.asList(BspUtils.getGlobalAggregatorClassNames(conf));
             private FrameTupleAccessor accessor = new FrameTupleAccessor(ctx.getFrameSize(),
                     inputRdFactory.createRecordDescriptor(ctx));
             private ByteBufferInputStream inputStream = new ByteBufferInputStream();
             private DataInput input = new DataInputStream(inputStream);
-            private Writable partialAggregateValue = BspUtils.createFinalAggregateValue(conf);
+            private List<Writable> partialAggregateValues = BspUtils.createFinalAggregateValues(conf);
 
             @Override
             public void open() throws HyracksDataException {
-                aggregator.init();
+                for (GlobalAggregator aggregator : aggregators) {
+                    aggregator.init();
+                }
             }
 
             @SuppressWarnings("unchecked")
@@ -82,11 +88,14 @@
                 int tupleCount = accessor.getTupleCount();
                 try {
                     for (int i = 0; i < tupleCount; i++) {
-                        int start = accessor.getFieldSlotsLength() + accessor.getTupleStartOffset(i)
-                                + accessor.getFieldStartOffset(i, 0);
-                        inputStream.setByteBuffer(buffer, start);
-                        partialAggregateValue.readFields(input);
-                        aggregator.step(partialAggregateValue);
+                        // iterate over all the aggregators
+                        for (int j = 0; j < partialAggregateValues.size(); j++) {
+                            int start = accessor.getFieldSlotsLength() + accessor.getTupleStartOffset(i)
+                                    + accessor.getFieldStartOffset(i, j);
+                            inputStream.setByteBuffer(buffer, start);
+                            partialAggregateValues.get(j).readFields(input);
+                            aggregators.get(j).step(partialAggregateValues.get(j));
+                        }
                     }
                 } catch (Exception e) {
                     throw new HyracksDataException(e);
@@ -102,6 +111,7 @@
             @Override
             public void close() throws HyracksDataException {
                 try {
+                    List<Writable> aggValues = new ArrayList<Writable>();
                     // iterate over hdfs spilled aggregates
                     FileSystem dfs = FileSystem.get(conf);
                     String spillingDir = BspUtils.getGlobalAggregateSpillingDirName(conf, Vertex.getSuperstep());
@@ -111,12 +121,20 @@
                         for (int i = 0; i < files.length; i++) {
                             FileStatus file = files[i];
                             DataInput dis = dfs.open(file.getPath());
-                            partialAggregateValue.readFields(dis);
-                            aggregator.step(partialAggregateValue);
+                            for (int j = 0; j < partialAggregateValues.size(); j++) {
+                                GlobalAggregator aggregator = aggregators.get(j);
+                                Writable partialAggregateValue = partialAggregateValues.get(j);
+                                partialAggregateValue.readFields(dis);
+                                aggregator.step(partialAggregateValue);
+                            }
                         }
                     }
-                    Writable finalAggregateValue = aggregator.finishFinal();
-                    IterationUtils.writeGlobalAggregateValue(conf, jobId, finalAggregateValue);
+                    for (int j = 0; j < partialAggregateValues.size(); j++) {
+                        GlobalAggregator aggregator = aggregators.get(j);
+                        Writable finalAggregateValue = aggregator.finishFinal();
+                        aggValues.add(finalAggregateValue);
+                    }
+                    IterationUtils.writeGlobalAggregateValue(conf, jobId, aggregateClassNames, aggValues);
                 } catch (IOException e) {
                     throw new HyracksDataException(e);
                 }
diff --git a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
index 8052b7c..6de65ca 100644
--- a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
+++ b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
@@ -15,6 +15,7 @@
 package edu.uci.ics.pregelix.dataflow.util;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.hadoop.conf.Configuration;
@@ -98,14 +99,20 @@
         }
     }
 
-    public static void writeGlobalAggregateValue(Configuration conf, String pregelixJobId, Writable agg)
-            throws HyracksDataException {
+    public static void writeGlobalAggregateValue(Configuration conf, String pregelixJobId, List<String> aggClassNames,
+            List<Writable> aggs) throws HyracksDataException {
         try {
             FileSystem dfs = FileSystem.get(conf);
             String pathStr = IterationUtils.TMP_DIR + pregelixJobId + "agg";
             Path path = new Path(pathStr);
-            FSDataOutputStream output = dfs.create(path, true);
-            agg.write(output);
+            FSDataOutputStream output;
+            output = dfs.create(path, true);
+            for (int i = 0; i < aggs.size(); i++) {
+                //write agg class name
+                output.writeUTF(aggClassNames.get(i));
+                // write the agg value
+                aggs.get(i).write(output);
+            }
             output.flush();
             output.close();
         } catch (IOException e) {
@@ -135,16 +142,26 @@
         return JobStateUtils.readForceTerminationState(conf, jobId);
     }
 
-    public static Writable readGlobalAggregateValue(Configuration conf, String jobId) throws HyracksDataException {
+    public static Writable readGlobalAggregateValue(Configuration conf, String jobId, String aggClassName)
+            throws HyracksDataException {
         try {
             FileSystem dfs = FileSystem.get(conf);
             String pathStr = IterationUtils.TMP_DIR + jobId + "agg";
             Path path = new Path(pathStr);
             FSDataInputStream input = dfs.open(path);
-            Writable agg = BspUtils.createFinalAggregateValue(conf);
-            agg.readFields(input);
-            input.close();
-            return agg;
+            int numOfAggs = BspUtils.createFinalAggregateValues(conf).size();
+            for (int i = 0; i < numOfAggs; i++) {
+                String aggName = input.readUTF();
+                Writable agg = BspUtils.createFinalAggregateValue(conf, aggName);
+                if (aggName.equals(aggClassName)) {
+                    agg.readFields(input);
+                    input.close();
+                    return agg;
+                } else {
+                    agg.readFields(input);
+                }
+            }
+            throw new IllegalStateException("Cannot find the aggregate value for " + aggClassName);
         } catch (IOException e) {
             throw new HyracksDataException(e);
         }
diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java
index 13c3bf5..c5374c1 100644
--- a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/maximalclique/MaximalCliqueVertex.java
@@ -277,7 +277,7 @@
     private static CliquesWritable readMaximalCliqueResult(Configuration conf) {
         try {
             CliquesWritable result = (CliquesWritable) IterationUtils.readGlobalAggregateValue(conf,
-                    BspUtils.getJobId(conf));
+                    BspUtils.getJobId(conf), MaximalCliqueAggregator.class.getName());
             return result;
         } catch (IOException e) {
             throw new IllegalStateException(e);
@@ -287,7 +287,7 @@
     public static void main(String[] args) throws Exception {
         PregelixJob job = new PregelixJob(TriangleCountingVertex.class.getSimpleName());
         job.setVertexClass(MaximalCliqueVertex.class);
-        job.setGlobalAggregatorClass(MaximalCliqueAggregator.class);
+        job.addGlobalAggregatorClass(MaximalCliqueAggregator.class);
         job.setDynamicVertexValueSize(true);
         job.setVertexInputFormatClass(TextMaximalCliqueInputFormat.class);
         job.setVertexOutputFormatClass(MaximalCliqueVertexOutputFormat.class);
diff --git a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/trianglecounting/TriangleCountingVertex.java b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/trianglecounting/TriangleCountingVertex.java
index a8d85ab..cf753bb 100644
--- a/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/trianglecounting/TriangleCountingVertex.java
+++ b/pregelix/pregelix-example/src/main/java/edu/uci/ics/pregelix/example/trianglecounting/TriangleCountingVertex.java
@@ -135,8 +135,8 @@
 
     private static long readTriangleCountingResult(Configuration conf) {
         try {
-            VLongWritable count = (VLongWritable) IterationUtils
-                    .readGlobalAggregateValue(conf, BspUtils.getJobId(conf));
+            VLongWritable count = (VLongWritable) IterationUtils.readGlobalAggregateValue(conf,
+                    BspUtils.getJobId(conf), TriangleCountingAggregator.class.getName());
             return count.get();
         } catch (IOException e) {
             throw new IllegalStateException(e);
@@ -146,7 +146,7 @@
     public static void main(String[] args) throws Exception {
         PregelixJob job = new PregelixJob(TriangleCountingVertex.class.getSimpleName());
         job.setVertexClass(TriangleCountingVertex.class);
-        job.setGlobalAggregatorClass(TriangleCountingAggregator.class);
+        job.addGlobalAggregatorClass(TriangleCountingAggregator.class);
         job.setVertexInputFormatClass(TextTriangleCountingInputFormat.class);
         job.setVertexOutputFormatClass(TriangleCountingVertexOutputFormat.class);
         job.setNoramlizedKeyComputerClass(VLongNormalizedKeyComputer.class);
diff --git a/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/OverflowAggregatorTest.java b/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/OverflowAggregatorTest.java
index 474d0a6..9badc78 100644
--- a/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/OverflowAggregatorTest.java
+++ b/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/OverflowAggregatorTest.java
@@ -59,7 +59,7 @@
             FileInputFormat.setInputPaths(job, INPUTPATH);
             FileOutputFormat.setOutputPath(job, new Path(OUTPUTPAH));
             job.getConfiguration().setLong(PregelixJob.NUM_VERTICE, 20);
-            job.setGlobalAggregatorClass(OverflowAggregator.class);
+            job.addGlobalAggregatorClass(OverflowAggregator.class);
 
             testCluster.setUp();
             Driver driver = new Driver(PageRankVertex.class);
@@ -67,7 +67,7 @@
 
             TestUtils.compareWithResultDir(new File(EXPECTEDPATH), new File(OUTPUTPAH));
             Text text = (Text) IterationUtils.readGlobalAggregateValue(job.getConfiguration(),
-                    BspUtils.getJobId(job.getConfiguration()));
+                    BspUtils.getJobId(job.getConfiguration()), OverflowAggregator.class.getName());
             Assert.assertEquals(text.getLength(), 20 * 32767);
         } catch (Exception e) {
             throw e;
diff --git a/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/jobgen/JobGenerator.java b/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/jobgen/JobGenerator.java
index 2dfd071..6ccefd2 100644
--- a/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/jobgen/JobGenerator.java
+++ b/pregelix/pregelix-example/src/test/java/edu/uci/ics/pregelix/example/jobgen/JobGenerator.java
@@ -231,7 +231,7 @@
     private static void generateTriangleCountingJob(String jobName, String outputPath) throws IOException {
         PregelixJob job = new PregelixJob(jobName);
         job.setVertexClass(TriangleCountingVertex.class);
-        job.setGlobalAggregatorClass(TriangleCountingAggregator.class);
+        job.addGlobalAggregatorClass(TriangleCountingAggregator.class);
         job.setVertexInputFormatClass(TextTriangleCountingInputFormat.class);
         job.setVertexOutputFormatClass(TriangleCountingVertexOutputFormat.class);
         job.setNoramlizedKeyComputerClass(VLongNormalizedKeyComputer.class);
@@ -243,7 +243,7 @@
     private static void generateMaximalCliqueJob(String jobName, String outputPath) throws IOException {
         PregelixJob job = new PregelixJob(jobName);
         job.setVertexClass(MaximalCliqueVertex.class);
-        job.setGlobalAggregatorClass(MaximalCliqueAggregator.class);
+        job.addGlobalAggregatorClass(MaximalCliqueAggregator.class);
         job.setDynamicVertexValueSize(true);
         job.setVertexInputFormatClass(TextMaximalCliqueInputFormat.class);
         job.setVertexOutputFormatClass(MaximalCliqueVertexOutputFormat.class);
@@ -257,7 +257,7 @@
     private static void generateMaximalCliqueJob2(String jobName, String outputPath) throws IOException {
         PregelixJob job = new PregelixJob(jobName);
         job.setVertexClass(MaximalCliqueVertex.class);
-        job.setGlobalAggregatorClass(MaximalCliqueAggregator.class);
+        job.addGlobalAggregatorClass(MaximalCliqueAggregator.class);
         job.setDynamicVertexValueSize(true);
         job.setVertexInputFormatClass(TextMaximalCliqueInputFormat.class);
         job.setVertexOutputFormatClass(MaximalCliqueVertexOutputFormat.class);
@@ -271,7 +271,7 @@
     private static void generateMaximalCliqueJob3(String jobName, String outputPath) throws IOException {
         PregelixJob job = new PregelixJob(jobName);
         job.setVertexClass(MaximalCliqueVertex.class);
-        job.setGlobalAggregatorClass(MaximalCliqueAggregator.class);
+        job.addGlobalAggregatorClass(MaximalCliqueAggregator.class);
         job.setDynamicVertexValueSize(true);
         job.setVertexInputFormatClass(TextMaximalCliqueInputFormat.class);
         job.setVertexOutputFormatClass(MaximalCliqueVertexOutputFormat.class);
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsReal.xml b/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsReal.xml
index df72d9b..591446c 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsReal.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsReal.xml
@@ -125,6 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextConnectedComponentsInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsRealComplex.xml b/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsRealComplex.xml
index b0bf024..32c2a1a 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsRealComplex.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ConnectedComponentsRealComplex.xml
@@ -1,145 +1,146 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?><configuration>
-<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
-<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
-<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
-<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
-<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
-<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
-<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
-<property><name>mapred.submit.replication</name><value>10</value></property>
-<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
-<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
-<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
-<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
-<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
-<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
-<property><name>keep.failed.task.files</name><value>false</value></property>
-<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
-<property><name>io.bytes.per.checksum</name><value>512</value></property>
-<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
-<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
-<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
-<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
-<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
-<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
-<property><name>fs.checkpoint.period</name><value>3600</value></property>
-<property><name>mapred.child.tmp</name><value>./tmp</value></property>
-<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
-<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
-<property><name>hadoop.logfile.count</name><value>10</value></property>
-<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
-<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
-<property><name>io.map.index.skip</name><value>0</value></property>
-<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
-<property><name>mapred.output.compress</name><value>false</value></property>
-<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
-<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
-<property><name>fs.checkpoint.size</name><value>67108864</value></property>
-<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
-<property><name>mapred.job.name</name><value>ConnectedComponents</value></property>
-<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
-<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>fs.s3n.impl</name><value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value></property>
-<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
-<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
-<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
-<property><name>mapred.task.timeout</name><value>600000</value></property>
-<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
-<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
-<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
-<property><name>ipc.client.kill.max</name><value>10</value></property>
-<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
-<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
-<property><name>io.sort.record.percent</name><value>0.05</value></property>
-<property><name>hadoop.security.authorization</name><value>false</value></property>
-<property><name>mapred.max.tracker.failures</name><value>4</value></property>
-<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
-<property><name>pregelix.numVertices</name><value>23</value></property>
-<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
-<property><name>mapred.map.tasks</name><value>2</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
-<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
-<property><name>fs.default.name</name><value>file:///</value></property>
-<property><name>tasktracker.http.threads</name><value>40</value></property>
-<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
-<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
-<property><name>mapred.reduce.tasks</name><value>1</value></property>
-<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
-<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex</value></property>
-<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
-<property><name>io.file.buffer.size</name><value>4096</value></property>
-<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
-<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
-<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
-<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
-<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
-<property><name>hadoop.native.lib</name><value>true</value></property>
-<property><name>fs.s3.block.size</name><value>67108864</value></property>
-<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
-<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
-<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
-<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
-<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
-<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
-<property><name>mapred.queue.names</name><value>default</value></property>
-<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
-<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
-<property><name>mapred.job.tracker</name><value>local</value></property>
-<property><name>io.skip.checksum.errors</name><value>false</value></property>
-<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
-<property><name>fs.s3.maxRetries</name><value>4</value></property>
-<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
-<property><name>fs.trash.interval</name><value>0</value></property>
-<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
-<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
-<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
-<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
-<property><name>io.sort.mb</name><value>100</value></property>
-<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
-<property><name>io.sort.factor</name><value>10</value></property>
-<property><name>mapred.task.profile</name><value>false</value></property>
-<property><name>job.end.retry.interval</name><value>30000</value></property>
-<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
-<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
-<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
-<property><name>webinterface.private.actions</name><value>false</value></property>
-<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
-<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex$SimpleMinCombiner</value></property>
-<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
-<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
-<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
-<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.compress.map.output</name><value>false</value></property>
-<property><name>io.sort.spill.percent</name><value>0.80</value></property>
-<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
-<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
-<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
-<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
-<property><name>job.end.retry.attempts</name><value>0</value></property>
-<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
-<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex$SimpleConnectedComponentsVertexOutputFormat</value></property>
-<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
-<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
-<property><name>pregelix.partitionerClass</name><value>edu.uci.ics.pregelix.api.util.DefaultVertexPartitioner</value></property>
-<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
-<property><name>hadoop.logfile.size</name><value>10000000</value></property>
-<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextConnectedComponentsInputFormat</value></property>
-<property><name>mapred.job.queue.name</name><value>default</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
-<property><name>pregelix.incStateLength</name><value>true</value></property>
-<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
-<property><name>topology.script.number.args</name><value>100</value></property>
-<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
-<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
 <property><name>mapred.task.cache.levels</name><value>2</value></property>
-<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
-<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
-<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
+<property><name>hadoop.native.lib</name><value>true</value></property>
+<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
+<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
+<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
+<property><name>io.skip.checksum.errors</name><value>false</value></property>
+<property><name>fs.default.name</name><value>file:///</value></property>
+<property><name>mapred.child.tmp</name><value>./tmp</value></property>
+<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
+<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
+<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
+<property><name>io.sort.factor</name><value>10</value></property>
+<property><name>mapred.task.timeout</name><value>600000</value></property>
+<property><name>mapred.max.tracker.failures</name><value>4</value></property>
+<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
+<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
+<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
+<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
+<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
+<property><name>tasktracker.http.threads</name><value>40</value></property>
+<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
+<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
+<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex$SimpleMinCombiner</value></property>
+<property><name>mapred.output.compress</name><value>false</value></property>
+<property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
+<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
+<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
+<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
+<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
+<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
+<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
+<property><name>job.end.retry.attempts</name><value>0</value></property>
+<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
+<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
+<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
+<property><name>topology.script.number.args</name><value>100</value></property>
+<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
+<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
+<property><name>pregelix.partitionerClass</name><value>edu.uci.ics.pregelix.api.util.DefaultVertexPartitioner</value></property>
+<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
+<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
+<property><name>pregelix.numVertices</name><value>23</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
+<property><name>hadoop.security.authorization</name><value>false</value></property>
+<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>mapred.min.split.size</name><value>0</value></property>
+<property><name>mapred.map.tasks</name><value>2</value></property>
+<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
+<property><name>mapred.job.queue.name</name><value>default</value></property>
+<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
+<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
+<property><name>job.end.retry.interval</name><value>30000</value></property>
+<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
+<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
+<property><name>mapred.reduce.tasks</name><value>1</value></property>
+<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
+<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
+<property><name>webinterface.private.actions</name><value>false</value></property>
+<property><name>io.sort.spill.percent</name><value>0.80</value></property>
+<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
+<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
+<property><name>mapred.job.name</name><value>ConnectedComponents</value></property>
+<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
 <property><name>mapred.map.max.attempts</name><value>4</value></property>
-<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>pregelix.incStateLength</name><value>true</value></property>
+<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
+<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
+<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
+<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
+<property><name>keep.failed.task.files</name><value>false</value></property>
 <property><name>ipc.client.tcpnodelay</name><value>false</value></property>
+<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
+<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>io.map.index.skip</name><value>0</value></property>
+<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
+<property><name>hadoop.logfile.size</name><value>10000000</value></property>
+<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
+<property><name>fs.checkpoint.period</name><value>3600</value></property>
+<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
+<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
+<property><name>fs.s3.maxRetries</name><value>4</value></property>
+<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
+<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
+<property><name>fs.trash.interval</name><value>0</value></property>
+<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
+<property><name>mapred.submit.replication</name><value>10</value></property>
+<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
+<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
+<property><name>mapred.job.tracker</name><value>local</value></property>
+<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
+<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
+<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
+<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
+<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
+<property><name>io.sort.record.percent</name><value>0.05</value></property>
+<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
+<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
+<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
+<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
+<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
+<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
+<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
+<property><name>hadoop.logfile.count</name><value>10</value></property>
+<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
+<property><name>fs.s3.block.size</name><value>67108864</value></property>
+<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
 <property><name>mapred.acls.enabled</name><value>false</value></property>
+<property><name>mapred.queue.names</name><value>default</value></property>
+<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
+<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
+<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex</value></property>
+<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
+<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
+<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
+<property><name>io.sort.mb</name><value>100</value></property>
+<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
+<property><name>mapred.compress.map.output</name><value>false</value></property>
+<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
+<property><name>ipc.client.kill.max</name><value>10</value></property>
+<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
+<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
+<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
+<property><name>io.file.buffer.size</name><value>4096</value></property>
+<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
+<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
+<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextConnectedComponentsInputFormat</value></property>
+<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
+<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ConnectedComponentsVertex$SimpleConnectedComponentsVertexOutputFormat</value></property>
+<property><name>mapred.task.profile</name><value>false</value></property>
+<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
+<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
+<property><name>fs.checkpoint.size</name><value>67108864</value></property>
 </configuration>
\ No newline at end of file
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/EarlyTermination.xml b/pregelix/pregelix-example/src/test/resources/jobs/EarlyTermination.xml
index d908da8..d06068d 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/EarlyTermination.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/EarlyTermination.xml
@@ -124,6 +124,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/GraphMutation.xml b/pregelix/pregelix-example/src/test/resources/jobs/GraphMutation.xml
index d5ec8f1..01d85a5 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/GraphMutation.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/GraphMutation.xml
@@ -124,6 +124,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique.xml b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique.xml
index b4c42e6..072ea9e 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique.xml
@@ -124,7 +124,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.maximalclique.TextMaximalCliqueInputFormat</value></property>
-<property><name>pregelix.aggregatorClass</name><value>edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator,class edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique2.xml b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique2.xml
index 6cf075b..3ae367d 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique2.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique2.xml
@@ -124,7 +124,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.maximalclique.TextMaximalCliqueInputFormat</value></property>
-<property><name>pregelix.aggregatorClass</name><value>edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator,class edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique3.xml b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique3.xml
index 49e2e6f..6cb617f 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique3.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MaximalClique3.xml
@@ -125,7 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.maximalclique.TextMaximalCliqueInputFormat</value></property>
-<property><name>pregelix.aggregatorClass</name><value>edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator,class edu.uci.ics.pregelix.example.maximalclique.MaximalCliqueAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflow.xml b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflow.xml
index 8316c64..76d6e87 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflow.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflow.xml
@@ -125,6 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowFixedsize.xml b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowFixedsize.xml
index a894ccd..1f52250 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowFixedsize.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowFixedsize.xml
@@ -124,6 +124,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowLSM.xml b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowLSM.xml
index a9f8925..9d2c9e1 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowLSM.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/MessageOverflowLSM.xml
@@ -1,145 +1,146 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?><configuration>
-<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
-<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
-<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
-<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
-<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
-<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
-<property><name>mapred.input.dir</name><value>file:/webmap</value></property>
-<property><name>mapred.submit.replication</name><value>10</value></property>
-<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
-<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
-<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
-<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
-<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
-<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
-<property><name>keep.failed.task.files</name><value>false</value></property>
-<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
-<property><name>io.bytes.per.checksum</name><value>512</value></property>
-<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
-<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
-<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
-<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
-<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
-<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
-<property><name>fs.checkpoint.period</name><value>3600</value></property>
-<property><name>mapred.child.tmp</name><value>./tmp</value></property>
-<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
-<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
-<property><name>hadoop.logfile.count</name><value>10</value></property>
-<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
-<property><name>mapred.output.dir</name><value>/result</value></property>
-<property><name>io.map.index.skip</name><value>0</value></property>
-<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
-<property><name>mapred.output.compress</name><value>false</value></property>
-<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
-<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
-<property><name>fs.checkpoint.size</name><value>67108864</value></property>
-<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
-<property><name>mapred.job.name</name><value>Message Overflow LSM</value></property>
-<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
-<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>fs.s3n.impl</name><value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value></property>
-<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
-<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
-<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
-<property><name>mapred.task.timeout</name><value>600000</value></property>
-<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
-<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
-<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
-<property><name>ipc.client.kill.max</name><value>10</value></property>
-<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
-<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
-<property><name>io.sort.record.percent</name><value>0.05</value></property>
-<property><name>hadoop.security.authorization</name><value>false</value></property>
-<property><name>mapred.max.tracker.failures</name><value>4</value></property>
-<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
-<property><name>pregelix.numVertices</name><value>20</value></property>
-<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
-<property><name>mapred.map.tasks</name><value>2</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
-<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
-<property><name>fs.default.name</name><value>file:///</value></property>
-<property><name>tasktracker.http.threads</name><value>40</value></property>
-<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
-<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
-<property><name>mapred.reduce.tasks</name><value>1</value></property>
-<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
-<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.MessageOverflowVertex</value></property>
-<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
-<property><name>io.file.buffer.size</name><value>4096</value></property>
-<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
-<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
-<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
-<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
-<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
-<property><name>hadoop.native.lib</name><value>true</value></property>
-<property><name>fs.s3.block.size</name><value>67108864</value></property>
-<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
-<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
-<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
-<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
-<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
-<property><name>pregelix.updateIntensive</name><value>true</value></property>
-<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
-<property><name>mapred.queue.names</name><value>default</value></property>
-<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
-<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
-<property><name>mapred.job.tracker</name><value>local</value></property>
-<property><name>io.skip.checksum.errors</name><value>false</value></property>
-<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
-<property><name>fs.s3.maxRetries</name><value>4</value></property>
-<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
-<property><name>fs.trash.interval</name><value>0</value></property>
-<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
-<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
-<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
-<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
-<property><name>io.sort.mb</name><value>100</value></property>
-<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
-<property><name>io.sort.factor</name><value>10</value></property>
-<property><name>mapred.task.profile</name><value>false</value></property>
-<property><name>job.end.retry.interval</name><value>30000</value></property>
-<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
-<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
-<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
-<property><name>webinterface.private.actions</name><value>false</value></property>
-<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
-<property><name>pregelix.framesize</name><value>2048</value></property>
-<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
-<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
-<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
-<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.compress.map.output</name><value>false</value></property>
-<property><name>io.sort.spill.percent</name><value>0.80</value></property>
-<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
-<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
-<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
-<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
-<property><name>job.end.retry.attempts</name><value>0</value></property>
-<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
-<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.MessageOverflowVertex$SimpleMessageOverflowVertexOutputFormat</value></property>
-<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
-<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
-<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
-<property><name>hadoop.logfile.size</name><value>10000000</value></property>
-<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
-<property><name>mapred.job.queue.name</name><value>default</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
-<property><name>pregelix.incStateLength</name><value>true</value></property>
-<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
-<property><name>topology.script.number.args</name><value>100</value></property>
-<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
-<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
 <property><name>mapred.task.cache.levels</name><value>2</value></property>
-<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
-<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
-<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
+<property><name>hadoop.native.lib</name><value>true</value></property>
+<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
+<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
+<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
+<property><name>io.skip.checksum.errors</name><value>false</value></property>
+<property><name>fs.default.name</name><value>file:///</value></property>
+<property><name>mapred.child.tmp</name><value>./tmp</value></property>
+<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
+<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
+<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
+<property><name>io.sort.factor</name><value>10</value></property>
+<property><name>pregelix.updateIntensive</name><value>true</value></property>
+<property><name>mapred.task.timeout</name><value>600000</value></property>
+<property><name>mapred.max.tracker.failures</name><value>4</value></property>
+<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
+<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
+<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
+<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
+<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
+<property><name>pregelix.framesize</name><value>2048</value></property>
+<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
+<property><name>tasktracker.http.threads</name><value>40</value></property>
+<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
+<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
+<property><name>mapred.output.compress</name><value>false</value></property>
+<property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
+<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
+<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
+<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
+<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
+<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
+<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
+<property><name>job.end.retry.attempts</name><value>0</value></property>
+<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
+<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
+<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
+<property><name>topology.script.number.args</name><value>100</value></property>
+<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
+<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
+<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
+<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
+<property><name>pregelix.numVertices</name><value>20</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
+<property><name>hadoop.security.authorization</name><value>false</value></property>
+<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>mapred.min.split.size</name><value>0</value></property>
+<property><name>mapred.map.tasks</name><value>2</value></property>
+<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
+<property><name>mapred.job.queue.name</name><value>default</value></property>
+<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
+<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
+<property><name>job.end.retry.interval</name><value>30000</value></property>
+<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
+<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
+<property><name>mapred.reduce.tasks</name><value>1</value></property>
+<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
+<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
+<property><name>webinterface.private.actions</name><value>false</value></property>
+<property><name>io.sort.spill.percent</name><value>0.80</value></property>
+<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
+<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
+<property><name>mapred.job.name</name><value>Message Overflow LSM</value></property>
+<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
 <property><name>mapred.map.max.attempts</name><value>4</value></property>
-<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>pregelix.incStateLength</name><value>true</value></property>
+<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
+<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
+<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
+<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
+<property><name>keep.failed.task.files</name><value>false</value></property>
 <property><name>ipc.client.tcpnodelay</name><value>false</value></property>
+<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
+<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>io.map.index.skip</name><value>0</value></property>
+<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
+<property><name>hadoop.logfile.size</name><value>10000000</value></property>
+<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
+<property><name>fs.checkpoint.period</name><value>3600</value></property>
+<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
+<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
+<property><name>fs.s3.maxRetries</name><value>4</value></property>
+<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
+<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
+<property><name>fs.trash.interval</name><value>0</value></property>
+<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
+<property><name>mapred.submit.replication</name><value>10</value></property>
+<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
+<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
+<property><name>mapred.job.tracker</name><value>local</value></property>
+<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
+<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
+<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
+<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
+<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
+<property><name>io.sort.record.percent</name><value>0.05</value></property>
+<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
+<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
+<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
+<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
+<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
+<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
+<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
+<property><name>hadoop.logfile.count</name><value>10</value></property>
+<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
+<property><name>fs.s3.block.size</name><value>67108864</value></property>
+<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
 <property><name>mapred.acls.enabled</name><value>false</value></property>
+<property><name>mapred.queue.names</name><value>default</value></property>
+<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
+<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
+<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.MessageOverflowVertex</value></property>
+<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
+<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
+<property><name>mapred.output.dir</name><value>/result</value></property>
+<property><name>io.sort.mb</name><value>100</value></property>
+<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
+<property><name>mapred.compress.map.output</name><value>false</value></property>
+<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
+<property><name>ipc.client.kill.max</name><value>10</value></property>
+<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
+<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
+<property><name>mapred.input.dir</name><value>file:/webmap</value></property>
+<property><name>io.file.buffer.size</name><value>4096</value></property>
+<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
+<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
+<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
+<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.MessageOverflowVertex$SimpleMessageOverflowVertexOutputFormat</value></property>
+<property><name>mapred.task.profile</name><value>false</value></property>
+<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
+<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
+<property><name>fs.checkpoint.size</name><value>67108864</value></property>
 </configuration>
\ No newline at end of file
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/PageRank.xml b/pregelix/pregelix-example/src/test/resources/jobs/PageRank.xml
index d29b2da..f1c27ca 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/PageRank.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/PageRank.xml
@@ -125,6 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimulatedPageRankVertexInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>false</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/PageRankReal.xml b/pregelix/pregelix-example/src/test/resources/jobs/PageRankReal.xml
index 69f8154..dfb4e71 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/PageRankReal.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/PageRankReal.xml
@@ -1,145 +1,146 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?><configuration>
-<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
-<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
-<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
-<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
-<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
-<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
-<property><name>mapred.input.dir</name><value>file:/webmap</value></property>
-<property><name>mapred.submit.replication</name><value>10</value></property>
-<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
-<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
-<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
-<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
-<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
-<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
-<property><name>keep.failed.task.files</name><value>false</value></property>
-<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
-<property><name>io.bytes.per.checksum</name><value>512</value></property>
-<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
-<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
-<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
-<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
-<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
-<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
-<property><name>fs.checkpoint.period</name><value>3600</value></property>
-<property><name>mapred.child.tmp</name><value>./tmp</value></property>
-<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
-<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
-<property><name>hadoop.logfile.count</name><value>10</value></property>
-<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
-<property><name>mapred.output.dir</name><value>/result</value></property>
-<property><name>io.map.index.skip</name><value>0</value></property>
-<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
-<property><name>mapred.output.compress</name><value>false</value></property>
-<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
-<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
-<property><name>fs.checkpoint.size</name><value>67108864</value></property>
-<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
-<property><name>mapred.job.name</name><value>PageRank</value></property>
-<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
-<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>fs.s3n.impl</name><value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value></property>
-<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
-<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
-<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
-<property><name>mapred.task.timeout</name><value>600000</value></property>
-<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
-<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
-<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
-<property><name>ipc.client.kill.max</name><value>10</value></property>
-<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
-<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
-<property><name>io.sort.record.percent</name><value>0.05</value></property>
-<property><name>hadoop.security.authorization</name><value>false</value></property>
-<property><name>mapred.max.tracker.failures</name><value>4</value></property>
-<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
-<property><name>pregelix.numVertices</name><value>20</value></property>
-<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
-<property><name>mapred.map.tasks</name><value>2</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
-<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
-<property><name>fs.default.name</name><value>file:///</value></property>
-<property><name>tasktracker.http.threads</name><value>40</value></property>
-<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
-<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
-<property><name>mapred.reduce.tasks</name><value>1</value></property>
-<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
-<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex</value></property>
-<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
-<property><name>io.file.buffer.size</name><value>4096</value></property>
-<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
-<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
-<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
-<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
-<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
-<property><name>hadoop.native.lib</name><value>true</value></property>
-<property><name>fs.s3.block.size</name><value>67108864</value></property>
-<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
-<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
-<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
-<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
-<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
-<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
-<property><name>mapred.queue.names</name><value>default</value></property>
-<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
-<property><name>pregelix.checkpointHook</name><value>edu.uci.ics.pregelix.api.util.ConservativeCheckpointHook</value></property>
-<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
-<property><name>mapred.job.tracker</name><value>local</value></property>
-<property><name>io.skip.checksum.errors</name><value>false</value></property>
-<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
-<property><name>fs.s3.maxRetries</name><value>4</value></property>
-<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
-<property><name>fs.trash.interval</name><value>0</value></property>
-<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
-<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
-<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
-<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
-<property><name>io.sort.mb</name><value>100</value></property>
-<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
-<property><name>io.sort.factor</name><value>10</value></property>
-<property><name>mapred.task.profile</name><value>false</value></property>
-<property><name>job.end.retry.interval</name><value>30000</value></property>
-<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
-<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
-<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
-<property><name>webinterface.private.actions</name><value>false</value></property>
-<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
-<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimpleSumCombiner</value></property>
-<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
-<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
-<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
-<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.compress.map.output</name><value>false</value></property>
-<property><name>io.sort.spill.percent</name><value>0.80</value></property>
-<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
-<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
-<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
-<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
-<property><name>job.end.retry.attempts</name><value>0</value></property>
-<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
-<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimplePageRankVertexOutputFormat</value></property>
-<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
-<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
-<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
-<property><name>hadoop.logfile.size</name><value>10000000</value></property>
-<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
-<property><name>mapred.job.queue.name</name><value>default</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
-<property><name>pregelix.incStateLength</name><value>false</value></property>
-<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
-<property><name>topology.script.number.args</name><value>100</value></property>
-<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
-<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
 <property><name>mapred.task.cache.levels</name><value>2</value></property>
-<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
-<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
-<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
+<property><name>hadoop.native.lib</name><value>true</value></property>
+<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
+<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
+<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
+<property><name>io.skip.checksum.errors</name><value>false</value></property>
+<property><name>fs.default.name</name><value>file:///</value></property>
+<property><name>mapred.child.tmp</name><value>./tmp</value></property>
+<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
+<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
+<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
+<property><name>io.sort.factor</name><value>10</value></property>
+<property><name>pregelix.checkpointHook</name><value>edu.uci.ics.pregelix.api.util.ConservativeCheckpointHook</value></property>
+<property><name>mapred.task.timeout</name><value>600000</value></property>
+<property><name>mapred.max.tracker.failures</name><value>4</value></property>
+<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
+<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
+<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
+<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
+<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
+<property><name>tasktracker.http.threads</name><value>40</value></property>
+<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
+<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
+<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimpleSumCombiner</value></property>
+<property><name>mapred.output.compress</name><value>false</value></property>
+<property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
+<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
+<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
+<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
+<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
+<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
+<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
+<property><name>job.end.retry.attempts</name><value>0</value></property>
+<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
+<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
+<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
+<property><name>topology.script.number.args</name><value>100</value></property>
+<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
+<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
+<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
+<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
+<property><name>pregelix.numVertices</name><value>20</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
+<property><name>hadoop.security.authorization</name><value>false</value></property>
+<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>mapred.min.split.size</name><value>0</value></property>
+<property><name>mapred.map.tasks</name><value>2</value></property>
+<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
+<property><name>mapred.job.queue.name</name><value>default</value></property>
+<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
+<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
+<property><name>job.end.retry.interval</name><value>30000</value></property>
+<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
+<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
+<property><name>mapred.reduce.tasks</name><value>1</value></property>
+<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
+<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
+<property><name>webinterface.private.actions</name><value>false</value></property>
+<property><name>io.sort.spill.percent</name><value>0.80</value></property>
+<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
+<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
+<property><name>mapred.job.name</name><value>PageRank</value></property>
+<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
 <property><name>mapred.map.max.attempts</name><value>4</value></property>
-<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>pregelix.incStateLength</name><value>false</value></property>
+<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
+<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
+<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
+<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
+<property><name>keep.failed.task.files</name><value>false</value></property>
 <property><name>ipc.client.tcpnodelay</name><value>false</value></property>
+<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
+<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>io.map.index.skip</name><value>0</value></property>
+<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
+<property><name>hadoop.logfile.size</name><value>10000000</value></property>
+<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
+<property><name>fs.checkpoint.period</name><value>3600</value></property>
+<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
+<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
+<property><name>fs.s3.maxRetries</name><value>4</value></property>
+<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
+<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
+<property><name>fs.trash.interval</name><value>0</value></property>
+<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
+<property><name>mapred.submit.replication</name><value>10</value></property>
+<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
+<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
+<property><name>mapred.job.tracker</name><value>local</value></property>
+<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
+<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
+<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
+<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
+<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
+<property><name>io.sort.record.percent</name><value>0.05</value></property>
+<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
+<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
+<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
+<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
+<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
+<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
+<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
+<property><name>hadoop.logfile.count</name><value>10</value></property>
+<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
+<property><name>fs.s3.block.size</name><value>67108864</value></property>
+<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
 <property><name>mapred.acls.enabled</name><value>false</value></property>
+<property><name>mapred.queue.names</name><value>default</value></property>
+<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
+<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
+<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex</value></property>
+<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
+<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
+<property><name>mapred.output.dir</name><value>/result</value></property>
+<property><name>io.sort.mb</name><value>100</value></property>
+<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
+<property><name>mapred.compress.map.output</name><value>false</value></property>
+<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
+<property><name>ipc.client.kill.max</name><value>10</value></property>
+<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
+<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
+<property><name>mapred.input.dir</name><value>file:/webmap</value></property>
+<property><name>io.file.buffer.size</name><value>4096</value></property>
+<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
+<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
+<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
+<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimplePageRankVertexOutputFormat</value></property>
+<property><name>mapred.task.profile</name><value>false</value></property>
+<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
+<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
+<property><name>fs.checkpoint.size</name><value>67108864</value></property>
 </configuration>
\ No newline at end of file
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealComplex.xml b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealComplex.xml
index 04fc686..49a6e20 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealComplex.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealComplex.xml
@@ -30,6 +30,7 @@
 <property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimpleSumCombiner</value></property>
 <property><name>mapred.output.compress</name><value>false</value></property>
 <property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
 <property><name>mapred.reduce.max.attempts</name><value>4</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealDynamic.xml b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealDynamic.xml
index c05a4da..789ea32 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealDynamic.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealDynamic.xml
@@ -125,6 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>true</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealNoCombiner.xml b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealNoCombiner.xml
index 8969fd7..796b1d1 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealNoCombiner.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/PageRankRealNoCombiner.xml
@@ -125,6 +125,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextPageRankInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>pregelix.incStateLength</name><value>false</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplex.xml b/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplex.xml
index 225429a..8834ead 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplex.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplex.xml
@@ -1,145 +1,146 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?><configuration>
-<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
-<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
-<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
-<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
-<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
-<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
-<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
-<property><name>mapred.submit.replication</name><value>10</value></property>
-<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
-<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
-<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
-<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
-<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
-<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
-<property><name>keep.failed.task.files</name><value>false</value></property>
-<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
-<property><name>io.bytes.per.checksum</name><value>512</value></property>
-<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
-<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
-<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
-<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
-<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
-<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
-<property><name>fs.checkpoint.period</name><value>3600</value></property>
-<property><name>mapred.child.tmp</name><value>./tmp</value></property>
-<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
-<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
-<property><name>hadoop.logfile.count</name><value>10</value></property>
-<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
-<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
-<property><name>io.map.index.skip</name><value>0</value></property>
-<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
-<property><name>mapred.output.compress</name><value>false</value></property>
-<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
-<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
-<property><name>fs.checkpoint.size</name><value>67108864</value></property>
-<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
-<property><name>mapred.job.name</name><value>Reachibility</value></property>
-<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
-<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>fs.s3n.impl</name><value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value></property>
-<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
-<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
-<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
-<property><name>mapred.task.timeout</name><value>600000</value></property>
-<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
-<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
-<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
-<property><name>ipc.client.kill.max</name><value>10</value></property>
-<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
-<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
-<property><name>io.sort.record.percent</name><value>0.05</value></property>
-<property><name>hadoop.security.authorization</name><value>false</value></property>
-<property><name>mapred.max.tracker.failures</name><value>4</value></property>
-<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
-<property><name>pregelix.numVertices</name><value>23</value></property>
-<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
-<property><name>mapred.map.tasks</name><value>2</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
-<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
-<property><name>fs.default.name</name><value>file:///</value></property>
-<property><name>tasktracker.http.threads</name><value>40</value></property>
-<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
-<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
-<property><name>mapred.reduce.tasks</name><value>1</value></property>
-<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
-<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex</value></property>
-<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
-<property><name>io.file.buffer.size</name><value>4096</value></property>
-<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
-<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
-<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
-<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
-<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
-<property><name>hadoop.native.lib</name><value>true</value></property>
-<property><name>fs.s3.block.size</name><value>67108864</value></property>
-<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
-<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
-<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
-<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
-<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
-<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
-<property><name>mapred.queue.names</name><value>default</value></property>
-<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
-<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
-<property><name>mapred.job.tracker</name><value>local</value></property>
-<property><name>io.skip.checksum.errors</name><value>false</value></property>
-<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
-<property><name>fs.s3.maxRetries</name><value>4</value></property>
-<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
-<property><name>ReachibilityVertex.destId</name><value>10</value></property>
-<property><name>fs.trash.interval</name><value>0</value></property>
-<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
-<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
-<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
-<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
-<property><name>io.sort.mb</name><value>100</value></property>
-<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
-<property><name>io.sort.factor</name><value>10</value></property>
-<property><name>mapred.task.profile</name><value>false</value></property>
-<property><name>job.end.retry.interval</name><value>30000</value></property>
-<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
-<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
-<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
-<property><name>webinterface.private.actions</name><value>false</value></property>
-<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
-<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityCombiner</value></property>
-<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
-<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
-<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
-<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.compress.map.output</name><value>false</value></property>
-<property><name>io.sort.spill.percent</name><value>0.80</value></property>
-<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
-<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
-<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
-<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
-<property><name>job.end.retry.attempts</name><value>0</value></property>
-<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
-<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityVertexOutputFormat</value></property>
-<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
-<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
-<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
-<property><name>hadoop.logfile.size</name><value>10000000</value></property>
-<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextReachibilityVertexInputFormat</value></property>
-<property><name>mapred.job.queue.name</name><value>default</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
-<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
-<property><name>ReachibilityVertex.sourceId</name><value>1</value></property>
-<property><name>topology.script.number.args</name><value>100</value></property>
-<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
-<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
 <property><name>mapred.task.cache.levels</name><value>2</value></property>
-<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
-<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
-<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
+<property><name>hadoop.native.lib</name><value>true</value></property>
+<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
+<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
+<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
+<property><name>io.skip.checksum.errors</name><value>false</value></property>
+<property><name>fs.default.name</name><value>file:///</value></property>
+<property><name>mapred.child.tmp</name><value>./tmp</value></property>
+<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
+<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
+<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
+<property><name>io.sort.factor</name><value>10</value></property>
+<property><name>mapred.task.timeout</name><value>600000</value></property>
+<property><name>mapred.max.tracker.failures</name><value>4</value></property>
+<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
+<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
+<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
+<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
+<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
+<property><name>tasktracker.http.threads</name><value>40</value></property>
+<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
+<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
+<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityCombiner</value></property>
+<property><name>mapred.output.compress</name><value>false</value></property>
+<property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
+<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
+<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
+<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
+<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
+<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
+<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
+<property><name>job.end.retry.attempts</name><value>0</value></property>
+<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
+<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
+<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
+<property><name>topology.script.number.args</name><value>100</value></property>
+<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
+<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
+<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
+<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
+<property><name>pregelix.numVertices</name><value>23</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
+<property><name>hadoop.security.authorization</name><value>false</value></property>
+<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>mapred.min.split.size</name><value>0</value></property>
+<property><name>mapred.map.tasks</name><value>2</value></property>
+<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
+<property><name>mapred.job.queue.name</name><value>default</value></property>
+<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
+<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
+<property><name>job.end.retry.interval</name><value>30000</value></property>
+<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
+<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
+<property><name>mapred.reduce.tasks</name><value>1</value></property>
+<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
+<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
+<property><name>webinterface.private.actions</name><value>false</value></property>
+<property><name>io.sort.spill.percent</name><value>0.80</value></property>
+<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
+<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
+<property><name>mapred.job.name</name><value>Reachibility</value></property>
+<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
 <property><name>mapred.map.max.attempts</name><value>4</value></property>
-<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
+<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
+<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
+<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
+<property><name>keep.failed.task.files</name><value>false</value></property>
 <property><name>ipc.client.tcpnodelay</name><value>false</value></property>
+<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
+<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>io.map.index.skip</name><value>0</value></property>
+<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
+<property><name>hadoop.logfile.size</name><value>10000000</value></property>
+<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
+<property><name>fs.checkpoint.period</name><value>3600</value></property>
+<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
+<property><name>ReachibilityVertex.sourceId</name><value>1</value></property>
+<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
+<property><name>fs.s3.maxRetries</name><value>4</value></property>
+<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
+<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
+<property><name>fs.trash.interval</name><value>0</value></property>
+<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
+<property><name>mapred.submit.replication</name><value>10</value></property>
+<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
+<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
+<property><name>mapred.job.tracker</name><value>local</value></property>
+<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
+<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
+<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
+<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
+<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
+<property><name>io.sort.record.percent</name><value>0.05</value></property>
+<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
+<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
+<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
+<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
+<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
+<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
+<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
+<property><name>hadoop.logfile.count</name><value>10</value></property>
+<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
+<property><name>fs.s3.block.size</name><value>67108864</value></property>
+<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
 <property><name>mapred.acls.enabled</name><value>false</value></property>
+<property><name>mapred.queue.names</name><value>default</value></property>
+<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
+<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
+<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex</value></property>
+<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
+<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
+<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
+<property><name>ReachibilityVertex.destId</name><value>10</value></property>
+<property><name>io.sort.mb</name><value>100</value></property>
+<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
+<property><name>mapred.compress.map.output</name><value>false</value></property>
+<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
+<property><name>ipc.client.kill.max</name><value>10</value></property>
+<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
+<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
+<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
+<property><name>io.file.buffer.size</name><value>4096</value></property>
+<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
+<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
+<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextReachibilityVertexInputFormat</value></property>
+<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
+<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityVertexOutputFormat</value></property>
+<property><name>mapred.task.profile</name><value>false</value></property>
+<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
+<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
+<property><name>fs.checkpoint.size</name><value>67108864</value></property>
 </configuration>
\ No newline at end of file
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplexNoConnectivity.xml b/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplexNoConnectivity.xml
index bd9da92..234dbf9 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplexNoConnectivity.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ReachibilityRealComplexNoConnectivity.xml
@@ -1,145 +1,146 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?><configuration>
-<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
-<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
-<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
-<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
-<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
-<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
-<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
-<property><name>mapred.submit.replication</name><value>10</value></property>
-<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
-<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
-<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
-<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
-<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
-<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
-<property><name>keep.failed.task.files</name><value>false</value></property>
-<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
-<property><name>io.bytes.per.checksum</name><value>512</value></property>
-<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
-<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
-<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
-<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
-<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
-<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
-<property><name>fs.checkpoint.period</name><value>3600</value></property>
-<property><name>mapred.child.tmp</name><value>./tmp</value></property>
-<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
-<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
-<property><name>hadoop.logfile.count</name><value>10</value></property>
-<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
-<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
-<property><name>io.map.index.skip</name><value>0</value></property>
-<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
-<property><name>mapred.output.compress</name><value>false</value></property>
-<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
-<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
-<property><name>fs.checkpoint.size</name><value>67108864</value></property>
-<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
-<property><name>mapred.job.name</name><value>Reachibility</value></property>
-<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
-<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>fs.s3n.impl</name><value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value></property>
-<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
-<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
-<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
-<property><name>mapred.task.timeout</name><value>600000</value></property>
-<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
-<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
-<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
-<property><name>ipc.client.kill.max</name><value>10</value></property>
-<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
-<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
-<property><name>io.sort.record.percent</name><value>0.05</value></property>
-<property><name>hadoop.security.authorization</name><value>false</value></property>
-<property><name>mapred.max.tracker.failures</name><value>4</value></property>
-<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
-<property><name>pregelix.numVertices</name><value>23</value></property>
-<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
-<property><name>mapred.map.tasks</name><value>2</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
-<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
-<property><name>fs.default.name</name><value>file:///</value></property>
-<property><name>tasktracker.http.threads</name><value>40</value></property>
-<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
-<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
-<property><name>mapred.reduce.tasks</name><value>1</value></property>
-<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
-<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex</value></property>
-<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
-<property><name>io.file.buffer.size</name><value>4096</value></property>
-<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
-<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
-<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
-<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
-<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
-<property><name>hadoop.native.lib</name><value>true</value></property>
-<property><name>fs.s3.block.size</name><value>67108864</value></property>
-<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
-<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
-<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
-<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
-<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
-<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
-<property><name>mapred.queue.names</name><value>default</value></property>
-<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
-<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
-<property><name>mapred.job.tracker</name><value>local</value></property>
-<property><name>io.skip.checksum.errors</name><value>false</value></property>
-<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
-<property><name>fs.s3.maxRetries</name><value>4</value></property>
-<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
-<property><name>ReachibilityVertex.destId</name><value>25</value></property>
-<property><name>fs.trash.interval</name><value>0</value></property>
-<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
-<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
-<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
-<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
-<property><name>io.sort.mb</name><value>100</value></property>
-<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
-<property><name>io.sort.factor</name><value>10</value></property>
-<property><name>mapred.task.profile</name><value>false</value></property>
-<property><name>job.end.retry.interval</name><value>30000</value></property>
-<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
-<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
-<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
-<property><name>webinterface.private.actions</name><value>false</value></property>
-<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
-<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityCombiner</value></property>
-<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
-<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
-<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
-<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
-<property><name>mapred.compress.map.output</name><value>false</value></property>
-<property><name>io.sort.spill.percent</name><value>0.80</value></property>
-<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
-<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
-<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
-<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
-<property><name>job.end.retry.attempts</name><value>0</value></property>
-<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
-<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityVertexOutputFormat</value></property>
-<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
-<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
-<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
-<property><name>hadoop.logfile.size</name><value>10000000</value></property>
-<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextReachibilityVertexInputFormat</value></property>
-<property><name>mapred.job.queue.name</name><value>default</value></property>
-<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
-<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
-<property><name>ReachibilityVertex.sourceId</name><value>1</value></property>
-<property><name>topology.script.number.args</name><value>100</value></property>
-<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
-<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
 <property><name>mapred.task.cache.levels</name><value>2</value></property>
-<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
-<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
-<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>hadoop.tmp.dir</name><value>/tmp/hadoop-${user.name}</value></property>
+<property><name>hadoop.native.lib</name><value>true</value></property>
+<property><name>map.sort.class</name><value>org.apache.hadoop.util.QuickSort</value></property>
+<property><name>ipc.client.idlethreshold</name><value>4000</value></property>
+<property><name>mapred.system.dir</name><value>${hadoop.tmp.dir}/mapred/system</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.hours</name><value>0</value></property>
+<property><name>io.skip.checksum.errors</name><value>false</value></property>
+<property><name>fs.default.name</name><value>file:///</value></property>
+<property><name>mapred.child.tmp</name><value>./tmp</value></property>
+<property><name>fs.har.impl.disable.cache</name><value>true</value></property>
+<property><name>mapred.skip.reduce.max.skip.groups</name><value>0</value></property>
+<property><name>mapred.jobtracker.instrumentation</name><value>org.apache.hadoop.mapred.JobTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.dns.nameserver</name><value>default</value></property>
+<property><name>io.sort.factor</name><value>10</value></property>
+<property><name>mapred.task.timeout</name><value>600000</value></property>
+<property><name>mapred.max.tracker.failures</name><value>4</value></property>
+<property><name>hadoop.rpc.socket.factory.class.default</name><value>org.apache.hadoop.net.StandardSocketFactory</value></property>
+<property><name>fs.hdfs.impl</name><value>org.apache.hadoop.hdfs.DistributedFileSystem</value></property>
+<property><name>mapred.queue.default.acl-administer-jobs</name><value>*</value></property>
+<property><name>mapred.queue.default.acl-submit-job</name><value>*</value></property>
+<property><name>mapred.skip.map.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.mapfile.bloom.size</name><value>1048576</value></property>
+<property><name>tasktracker.http.threads</name><value>40</value></property>
+<property><name>mapred.job.shuffle.merge.percent</name><value>0.66</value></property>
+<property><name>fs.ftp.impl</name><value>org.apache.hadoop.fs.ftp.FTPFileSystem</value></property>
+<property><name>pregelix.combinerClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityCombiner</value></property>
+<property><name>mapred.output.compress</name><value>false</value></property>
+<property><name>io.bytes.per.checksum</name><value>512</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
+<property><name>topology.node.switch.mapping.impl</name><value>org.apache.hadoop.net.ScriptBasedMapping</value></property>
+<property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
+<property><name>mapred.reduce.max.attempts</name><value>4</value></property>
+<property><name>fs.ramfs.impl</name><value>org.apache.hadoop.fs.InMemoryFileSystem</value></property>
+<property><name>mapred.skip.map.max.skip.records</name><value>0</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.dir</name><value>/jobtracker/jobsInfo</value></property>
+<property><name>fs.s3.buffer.dir</name><value>${hadoop.tmp.dir}/s3</value></property>
+<property><name>job.end.retry.attempts</name><value>0</value></property>
+<property><name>fs.file.impl</name><value>org.apache.hadoop.fs.LocalFileSystem</value></property>
+<property><name>mapred.local.dir.minspacestart</name><value>0</value></property>
+<property><name>mapred.output.compression.type</name><value>RECORD</value></property>
+<property><name>topology.script.number.args</name><value>100</value></property>
+<property><name>io.mapfile.bloom.error.rate</name><value>0.005</value></property>
+<property><name>mapred.max.tracker.blacklists</name><value>4</value></property>
+<property><name>mapred.task.profile.maps</name><value>0-2</value></property>
+<property><name>mapred.userlog.retain.hours</name><value>24</value></property>
+<property><name>pregelix.numVertices</name><value>23</value></property>
+<property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
+<property><name>hadoop.security.authorization</name><value>false</value></property>
+<property><name>local.cache.size</name><value>10737418240</value></property>
 <property><name>mapred.min.split.size</name><value>0</value></property>
+<property><name>mapred.map.tasks</name><value>2</value></property>
+<property><name>mapred.child.java.opts</name><value>-Xmx200m</value></property>
+<property><name>mapred.job.queue.name</name><value>default</value></property>
+<property><name>ipc.server.listen.queue.size</name><value>128</value></property>
+<property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
+<property><name>job.end.retry.interval</name><value>30000</value></property>
+<property><name>mapred.skip.attempts.to.start.skipping</name><value>2</value></property>
+<property><name>fs.checkpoint.dir</name><value>${hadoop.tmp.dir}/dfs/namesecondary</value></property>
+<property><name>mapred.reduce.tasks</name><value>1</value></property>
+<property><name>mapred.merge.recordsBeforeProgress</name><value>10000</value></property>
+<property><name>mapred.userlog.limit.kb</name><value>0</value></property>
+<property><name>webinterface.private.actions</name><value>false</value></property>
+<property><name>io.sort.spill.percent</name><value>0.80</value></property>
+<property><name>mapred.job.shuffle.input.buffer.percent</name><value>0.70</value></property>
+<property><name>mapred.map.tasks.speculative.execution</name><value>true</value></property>
+<property><name>mapred.job.name</name><value>Reachibility</value></property>
+<property><name>hadoop.util.hash.type</name><value>murmur</value></property>
 <property><name>mapred.map.max.attempts</name><value>4</value></property>
-<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.job.tracker.handler.count</name><value>10</value></property>
+<property><name>mapred.tasktracker.expiry.interval</name><value>600000</value></property>
+<property><name>mapred.jobtracker.maxtasks.per.job</name><value>-1</value></property>
+<property><name>mapred.jobtracker.job.history.block.size</name><value>3145728</value></property>
+<property><name>keep.failed.task.files</name><value>false</value></property>
 <property><name>ipc.client.tcpnodelay</name><value>false</value></property>
+<property><name>mapred.task.profile.reduces</name><value>0-2</value></property>
+<property><name>mapred.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>io.map.index.skip</name><value>0</value></property>
+<property><name>ipc.server.tcpnodelay</name><value>false</value></property>
+<property><name>hadoop.logfile.size</name><value>10000000</value></property>
+<property><name>mapred.reduce.tasks.speculative.execution</name><value>true</value></property>
+<property><name>fs.checkpoint.period</name><value>3600</value></property>
+<property><name>mapred.job.reuse.jvm.num.tasks</name><value>1</value></property>
+<property><name>ReachibilityVertex.sourceId</name><value>1</value></property>
+<property><name>mapred.jobtracker.completeuserjobs.maximum</name><value>100</value></property>
+<property><name>fs.s3.maxRetries</name><value>4</value></property>
+<property><name>mapred.local.dir</name><value>${hadoop.tmp.dir}/mapred/local</value></property>
+<property><name>fs.hftp.impl</name><value>org.apache.hadoop.hdfs.HftpFileSystem</value></property>
+<property><name>fs.trash.interval</name><value>0</value></property>
+<property><name>fs.s3.sleepTimeSeconds</name><value>10</value></property>
+<property><name>mapred.submit.replication</name><value>10</value></property>
+<property><name>fs.har.impl</name><value>org.apache.hadoop.fs.HarFileSystem</value></property>
+<property><name>mapred.map.output.compression.codec</name><value>org.apache.hadoop.io.compress.DefaultCodec</value></property>
+<property><name>mapred.tasktracker.dns.interface</name><value>default</value></property>
+<property><name>mapred.job.tracker</name><value>local</value></property>
+<property><name>io.seqfile.sorter.recordlimit</name><value>1000000</value></property>
+<property><name>mapred.line.input.format.linespermap</name><value>1</value></property>
+<property><name>mapred.jobtracker.taskScheduler</name><value>org.apache.hadoop.mapred.JobQueueTaskScheduler</value></property>
+<property><name>mapred.tasktracker.instrumentation</name><value>org.apache.hadoop.mapred.TaskTrackerMetricsInst</value></property>
+<property><name>mapred.tasktracker.procfsbasedprocesstree.sleeptime-before-sigkill</name><value>5000</value></property>
+<property><name>mapred.local.dir.minspacekill</name><value>0</value></property>
+<property><name>io.sort.record.percent</name><value>0.05</value></property>
+<property><name>fs.kfs.impl</name><value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value></property>
+<property><name>mapred.temp.dir</name><value>${hadoop.tmp.dir}/mapred/temp</value></property>
+<property><name>mapred.tasktracker.reduce.tasks.maximum</name><value>2</value></property>
+<property><name>fs.checkpoint.edits.dir</name><value>${fs.checkpoint.dir}</value></property>
+<property><name>mapred.job.reduce.input.buffer.percent</name><value>0.0</value></property>
+<property><name>mapred.tasktracker.indexcache.mb</name><value>10</value></property>
+<property><name>pregelix.nmkComputerClass</name><value>edu.uci.ics.pregelix.example.data.VLongNormalizedKeyComputer</value></property>
+<property><name>hadoop.logfile.count</name><value>10</value></property>
+<property><name>mapred.skip.reduce.auto.incr.proc.count</name><value>true</value></property>
+<property><name>io.seqfile.compress.blocksize</name><value>1000000</value></property>
+<property><name>fs.s3.block.size</name><value>67108864</value></property>
+<property><name>mapred.tasktracker.taskmemorymanager.monitoring-interval</name><value>5000</value></property>
 <property><name>mapred.acls.enabled</name><value>false</value></property>
+<property><name>mapred.queue.names</name><value>default</value></property>
+<property><name>fs.hsftp.impl</name><value>org.apache.hadoop.hdfs.HsftpFileSystem</value></property>
+<property><name>mapred.task.tracker.http.address</name><value>0.0.0.0:50060</value></property>
+<property><name>pregelix.vertexClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex</value></property>
+<property><name>mapred.reduce.parallel.copies</name><value>5</value></property>
+<property><name>io.seqfile.lazydecompress</name><value>true</value></property>
+<property><name>mapred.output.dir</name><value>/resultcomplex</value></property>
+<property><name>ReachibilityVertex.destId</name><value>25</value></property>
+<property><name>io.sort.mb</name><value>100</value></property>
+<property><name>ipc.client.connection.maxidletime</name><value>10000</value></property>
+<property><name>mapred.compress.map.output</name><value>false</value></property>
+<property><name>mapred.task.tracker.report.address</name><value>127.0.0.1:0</value></property>
+<property><name>ipc.client.kill.max</name><value>10</value></property>
+<property><name>ipc.client.connect.max.retries</name><value>10</value></property>
+<property><name>fs.s3.impl</name><value>org.apache.hadoop.fs.s3.S3FileSystem</value></property>
+<property><name>mapred.job.tracker.http.address</name><value>0.0.0.0:50030</value></property>
+<property><name>mapred.input.dir</name><value>file:/webmapcomplex</value></property>
+<property><name>io.file.buffer.size</name><value>4096</value></property>
+<property><name>mapred.jobtracker.restart.recover</name><value>false</value></property>
+<property><name>io.serializations</name><value>org.apache.hadoop.io.serializer.WritableSerialization</value></property>
+<property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextReachibilityVertexInputFormat</value></property>
+<property><name>mapred.reduce.copy.backoff</name><value>300</value></property>
+<property><name>pregelix.vertexOutputFormatClass</name><value>edu.uci.ics.pregelix.example.ReachabilityVertex$SimpleReachibilityVertexOutputFormat</value></property>
+<property><name>mapred.task.profile</name><value>false</value></property>
+<property><name>jobclient.output.filter</name><value>FAILED</value></property>
+<property><name>mapred.tasktracker.map.tasks.maximum</name><value>2</value></property>
+<property><name>io.compression.codecs</name><value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value></property>
+<property><name>fs.checkpoint.size</name><value>67108864</value></property>
 </configuration>
\ No newline at end of file
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ShortestPaths.xml b/pregelix/pregelix-example/src/test/resources/jobs/ShortestPaths.xml
index 9acd7bc..b1c57c5 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ShortestPaths.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ShortestPaths.xml
@@ -126,6 +126,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.PageRankVertex$SimulatedPageRankVertexInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/ShortestPathsReal.xml b/pregelix/pregelix-example/src/test/resources/jobs/ShortestPathsReal.xml
index 6c25575..f1d2dc6 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/ShortestPathsReal.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/ShortestPathsReal.xml
@@ -126,6 +126,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.inputformat.TextShortestPathsInputFormat</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-example/src/test/resources/jobs/TriangleCounting.xml b/pregelix/pregelix-example/src/test/resources/jobs/TriangleCounting.xml
index 4a40a6a..951ac6f 100644
--- a/pregelix/pregelix-example/src/test/resources/jobs/TriangleCounting.xml
+++ b/pregelix/pregelix-example/src/test/resources/jobs/TriangleCounting.xml
@@ -123,7 +123,7 @@
 <property><name>mapred.inmem.merge.threshold</name><value>1000</value></property>
 <property><name>hadoop.logfile.size</name><value>10000000</value></property>
 <property><name>pregelix.vertexInputFormatClass</name><value>edu.uci.ics.pregelix.example.trianglecounting.TextTriangleCountingInputFormat</value></property>
-<property><name>pregelix.aggregatorClass</name><value>edu.uci.ics.pregelix.example.trianglecounting.TriangleCountingAggregator</value></property>
+<property><name>pregelix.aggregatorClass</name><value>class edu.uci.ics.pregelix.api.util.GlobalCountAggregator,class edu.uci.ics.pregelix.example.trianglecounting.TriangleCountingAggregator</value></property>
 <property><name>mapred.job.queue.name</name><value>default</value></property>
 <property><name>mapred.job.tracker.persist.jobstatus.active</name><value>false</value></property>
 <property><name>mapred.reduce.slowstart.completed.maps</name><value>0.05</value></property>
diff --git a/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/ComputeUpdateFunctionFactory.java b/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/ComputeUpdateFunctionFactory.java
index a002be0..3e4a811 100644
--- a/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/ComputeUpdateFunctionFactory.java
+++ b/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/ComputeUpdateFunctionFactory.java
@@ -60,9 +60,9 @@
             private final ArrayTupleBuilder tbMsg = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbAlive = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbTerminate = new ArrayTupleBuilder(1);
-            private final ArrayTupleBuilder tbGlobalAggregate = new ArrayTupleBuilder(1);
             private final ArrayTupleBuilder tbInsert = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbDelete = new ArrayTupleBuilder(1);
+            private ArrayTupleBuilder tbGlobalAggregate;
 
             // for writing out to message channel
             private IFrameWriter writerMsg;
@@ -85,7 +85,7 @@
             private IFrameWriter writerGlobalAggregate;
             private FrameTupleAppender appenderGlobalAggregate;
             private ByteBuffer bufferGlobalAggregate;
-            private GlobalAggregator aggregator;
+            private List<GlobalAggregator> aggregators;
 
             // for writing out to insert vertex channel
             private IFrameWriter writerInsert;
@@ -114,8 +114,12 @@
                 this.conf = confFactory.createConfiguration(ctx);
                 //LSM index does not have in-place update
                 this.dynamicStateLength = BspUtils.getDynamicVertexValueSize(conf) || BspUtils.useLSM(conf);
-                this.aggregator = BspUtils.createGlobalAggregator(conf);
-                this.aggregator.init();
+                this.aggregators = BspUtils.createGlobalAggregators(conf);
+                for (int i = 0; i < aggregators.size(); i++) {
+                    this.aggregators.get(i).init();
+                }
+
+                this.tbGlobalAggregate = new ArrayTupleBuilder(aggregators.size());
 
                 this.writerMsg = writers[0];
                 this.bufferMsg = ctx.allocateFrame();
@@ -215,7 +219,9 @@
 
                 if (msgContentList.segmentEnd()) {
                     /** the if condition makes sure aggregate only calls once per-vertex */
-                    aggregator.step(vertex);
+                    for (int i = 0; i < aggregators.size(); i++) {
+                        aggregators.get(i).step(vertex);
+                    }
                 }
             }
 
@@ -237,13 +243,15 @@
 
             private void writeOutGlobalAggregate() throws HyracksDataException {
                 try {
-                    /**
-                     * get partial aggregate result and flush to the final
-                     * aggregator
-                     */
-                    Writable agg = aggregator.finishPartial();
-                    agg.write(tbGlobalAggregate.getDataOutput());
-                    tbGlobalAggregate.addFieldEndOffset();
+                    for (int i = 0; i < aggregators.size(); i++) {
+                        /**
+                         * get partial aggregate result and flush to the final
+                         * aggregator
+                         */
+                        Writable agg = aggregators.get(i).finishPartial();
+                        agg.write(tbGlobalAggregate.getDataOutput());
+                        tbGlobalAggregate.addFieldEndOffset();
+                    }
                     if (!appenderGlobalAggregate.append(tbGlobalAggregate.getFieldEndOffsets(),
                             tbGlobalAggregate.getByteArray(), 0, tbGlobalAggregate.getSize())) {
                         // aggregate state exceed the page size, write to HDFS
diff --git a/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/StartComputeUpdateFunctionFactory.java b/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/StartComputeUpdateFunctionFactory.java
index 1d26c83..9ddcce5 100644
--- a/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/StartComputeUpdateFunctionFactory.java
+++ b/pregelix/pregelix-runtime/src/main/java/edu/uci/ics/pregelix/runtime/function/StartComputeUpdateFunctionFactory.java
@@ -60,9 +60,9 @@
             private final ArrayTupleBuilder tbMsg = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbAlive = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbTerminate = new ArrayTupleBuilder(1);
-            private final ArrayTupleBuilder tbGlobalAggregate = new ArrayTupleBuilder(1);
             private final ArrayTupleBuilder tbInsert = new ArrayTupleBuilder(2);
             private final ArrayTupleBuilder tbDelete = new ArrayTupleBuilder(1);
+            private ArrayTupleBuilder tbGlobalAggregate;
 
             // for writing out to message channel
             private IFrameWriter writerMsg;
@@ -79,7 +79,7 @@
             private IFrameWriter writerGlobalAggregate;
             private FrameTupleAppender appenderGlobalAggregate;
             private ByteBuffer bufferGlobalAggregate;
-            private GlobalAggregator aggregator;
+            private List<GlobalAggregator> aggregators;
 
             // for writing out the global aggregate
             private IFrameWriter writerTerminate;
@@ -117,8 +117,12 @@
                 this.conf = confFactory.createConfiguration(ctx);
                 //LSM index does not have in-place update
                 this.dynamicStateLength = BspUtils.getDynamicVertexValueSize(conf) || BspUtils.useLSM(conf);;
-                this.aggregator = BspUtils.createGlobalAggregator(conf);
-                this.aggregator.init();
+                this.aggregators = BspUtils.createGlobalAggregators(conf);
+                for (int i = 0; i < aggregators.size(); i++) {
+                    this.aggregators.get(i).init();
+                }
+
+                this.tbGlobalAggregate = new ArrayTupleBuilder(aggregators.size());
 
                 this.writerMsg = writers[0];
                 this.bufferMsg = ctx.allocateFrame();
@@ -204,7 +208,9 @@
                 /**
                  * call the global aggregator
                  */
-                aggregator.step(vertex);
+                for (int i = 0; i < aggregators.size(); i++) {
+                    aggregators.get(i).step(vertex);
+                }
 
             }
 
@@ -226,13 +232,15 @@
 
             private void writeOutGlobalAggregate() throws HyracksDataException {
                 try {
-                    /**
-                     * get partial aggregate result and flush to the final
-                     * aggregator
-                     */
-                    Writable agg = aggregator.finishPartial();
-                    agg.write(tbGlobalAggregate.getDataOutput());
-                    tbGlobalAggregate.addFieldEndOffset();
+                    for (int i = 0; i < aggregators.size(); i++) {
+                        /**
+                         * get partial aggregate result and flush to the final
+                         * aggregator
+                         */
+                        Writable agg = aggregators.get(i).finishPartial();
+                        agg.write(tbGlobalAggregate.getDataOutput());
+                        tbGlobalAggregate.addFieldEndOffset();
+                    }
                     if (!appenderGlobalAggregate.append(tbGlobalAggregate.getFieldEndOffsets(),
                             tbGlobalAggregate.getByteArray(), 0, tbGlobalAggregate.getSize())) {
                         // aggregate state exceed the page size, write to HDFS