diff --git a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
index a188f64..d89d577 100644
--- a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
+++ b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
@@ -63,6 +63,7 @@
 import edu.uci.ics.hyracks.dataflow.std.file.FileSplit;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
 import edu.uci.ics.hyracks.dataflow.std.misc.ConstantTupleSourceOperatorDescriptor;
+import edu.uci.ics.hyracks.dataflow.std.sort.Algorithm;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.hdfs2.dataflow.HDFSReadOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.btree.dataflow.BTreeDataflowHelperFactory;
@@ -716,7 +717,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(lastCheckpointedIteration,
                 WritableComparator.get(vertexIdClass).getClass());
         ExternalSortOperatorDescriptor sort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, recordDescriptor);
+                nkmFactory, sortCmpFactories, recordDescriptor, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, sort);
 
         /**
diff --git a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
index 195e595..bbd3a7d 100644
--- a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
+++ b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
@@ -50,6 +50,7 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
 import edu.uci.ics.hyracks.dataflow.std.misc.ConstantTupleSourceOperatorDescriptor;
+import edu.uci.ics.hyracks.dataflow.std.sort.Algorithm;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.hdfs2.dataflow.HDFSReadOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.btree.dataflow.BTreeSearchOperatorDescriptor;
@@ -195,7 +196,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
@@ -282,8 +283,8 @@
 
         spec.connect(new MToNPartitioningConnectorDescriptor(spec, partionFactory), scanner, 5, btreeBulkLoad, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), localSort, 0, localGby, 0);
-        spec.connect(new MToNPartitioningMergingConnectorDescriptor(spec, partionFactory, keyFields, sortCmpFactories, nkmFactory),
-                localGby, 0, globalGby, 0);
+        spec.connect(new MToNPartitioningMergingConnectorDescriptor(spec, partionFactory, keyFields, sortCmpFactories,
+                nkmFactory), localGby, 0, globalGby, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), globalGby, 0, materialize, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), materialize, 0, postSuperStep, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), postSuperStep, 0, emptySink, 0);
@@ -401,7 +402,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
@@ -503,8 +504,8 @@
 
         spec.connect(new MToNPartitioningConnectorDescriptor(spec, partionFactory), join, 5, btreeBulkLoad, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), localSort, 0, localGby, 0);
-        spec.connect(new MToNPartitioningMergingConnectorDescriptor(spec, partionFactory, keyFields, sortCmpFactories, nkmFactory),
-                localGby, 0, globalGby, 0);
+        spec.connect(new MToNPartitioningMergingConnectorDescriptor(spec, partionFactory, keyFields, sortCmpFactories,
+                nkmFactory), localGby, 0, globalGby, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), globalGby, 0, materialize, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), materialize, 0, postSuperStep, 0);
         spec.connect(new OneToOneConnectorDescriptor(spec), postSuperStep, 0, emptySink, 0);
@@ -601,7 +602,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(lastSuccessfulIteration,
                 WritableComparator.get(vertexIdClass).getClass());
         ExternalSortOperatorDescriptor sort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, recordDescriptor);
+                nkmFactory, sortCmpFactories, recordDescriptor, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, sort);
 
         /**
diff --git a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
index cc90f2c..0bccde5 100644
--- a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
+++ b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
@@ -32,6 +32,7 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningMergingConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
+import edu.uci.ics.hyracks.dataflow.std.sort.Algorithm;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -138,7 +139,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
@@ -338,7 +339,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
diff --git a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
index 3b3c9e7..ae2621e 100644
--- a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
+++ b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
@@ -31,6 +31,7 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
+import edu.uci.ics.hyracks.dataflow.std.sort.Algorithm;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -140,7 +141,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor globalSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, globalSort);
 
         /**
@@ -327,7 +328,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor globalSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, globalSort);
 
         /**
diff --git a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
index e334095..7645cd6 100644
--- a/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
+++ b/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
@@ -31,6 +31,7 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
+import edu.uci.ics.hyracks.dataflow.std.sort.Algorithm;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -137,7 +138,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
@@ -153,7 +154,7 @@
          * construct global sort operator
          */
         ExternalSortOperatorDescriptor globalSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, globalSort);
 
         /**
@@ -341,7 +342,7 @@
         sortCmpFactories[0] = JobGenUtil.getIBinaryComparatorFactory(iteration, WritableComparator.get(vertexIdClass)
                 .getClass());
         ExternalSortOperatorDescriptor localSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, localSort);
 
         /**
@@ -357,7 +358,7 @@
          * construct global sort operator
          */
         ExternalSortOperatorDescriptor globalSort = new ExternalSortOperatorDescriptor(spec, maxFrameNumber, keyFields,
-                nkmFactory, sortCmpFactories, rdUnnestedMessage);
+                nkmFactory, sortCmpFactories, rdUnnestedMessage, Algorithm.QUICK_SORT);
         ClusterConfig.setLocationConstraint(spec, globalSort);
 
         /**