diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
index 6baf86c..0232054 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
@@ -33,33 +33,22 @@
     private float averageCoverage;
     
     // merge/update directions
+    
+    // merge/update directions
     public static class DirectionFlag {
         public static final byte DIR_FF = 0b00 << 0;
         public static final byte DIR_FR = 0b01 << 0;
         public static final byte DIR_RF = 0b10 << 0;
         public static final byte DIR_RR = 0b11 << 0;
         public static final byte DIR_MASK = 0b11 << 0;
-    }
-    
-    public enum Dir {
-        FF(0b00 << 0),
-        FR(0b01 << 0),
-        RF(0b10 << 0),
-        RR(0b11 << 0);
         
-		private byte value;
-        private Dir(int val) {
-            value = (byte) val;
-        }
-        public byte getValue() {
-        	return value;
-        }
+        public static final byte[] values = {DIR_FF, DIR_FR, DIR_RF, DIR_RR};
     }
-    
+        
     public NodeWritable() {
-        for (Dir d: Dir.values()) {
-            edges[d.getValue()] = new VKmerListWritable();
-            threads[d.getValue()] = new PositionListWritable();
+        for (byte d: DirectionFlag.values) {
+            edges[d] = new VKmerListWritable();
+            threads[d] = new PositionListWritable();
         }
         startReads = new PositionListWritable();
         endReads = new PositionListWritable();
@@ -81,30 +70,26 @@
     public void set(VKmerListWritable[] edges, PositionListWritable[] threads,
             PositionListWritable startReads, PositionListWritable endReads, 
             VKmerBytesWritable kmer2, float coverage) {
-        for (Dir d: Dir.values()) {
-            this.edges[d.getValue()].setCopy(edges[d.getValue()]);
-            this.threads[d.getValue()].set(threads[d.getValue()]);
+        for (byte d: DirectionFlag.values) {
+            this.edges[d].setCopy(edges[d]);
+            this.threads[d].set(threads[d]);
         }
+        this.startReads.set(startReads);
+        this.endReads.set(endReads);
         this.kmer.setAsCopy(kmer2);
         this.averageCoverage = coverage;
     }
 
     public void reset() {
-        for (Dir d: Dir.values()) {
-            edges[d.getValue()].reset();
-            threads[d.getValue()].reset();
+        for (byte d: DirectionFlag.values) {
+            edges[d].reset();
+            threads[d].reset();
         }
+        startReads.reset();
+        endReads.reset();
         this.kmer.reset(0);
         averageCoverage = 0;
     }
-    
-    public PositionListWritable getNodeIdList() {
-        return nodeIdList;
-    }
-
-    public void setNodeIdList(PositionListWritable nodeIdList) {
-        this.nodeIdList.set(nodeIdList);
-    }
 
     public VKmerBytesWritable getKmer() {
         return kmer;
@@ -119,35 +104,35 @@
     }
     
     public VKmerListWritable getFFList() {
-        return forwardForwardList;
+        return edges[DirectionFlag.DIR_FF];
     }
 
     public VKmerListWritable getFRList() {
-        return forwardReverseList;
+        return edges[DirectionFlag.DIR_FR];
     }
 
     public VKmerListWritable getRFList() {
-        return reverseForwardList;
+        return edges[DirectionFlag.DIR_RF];
     }
 
     public VKmerListWritable getRRList() {
-        return reverseReverseList;
+        return edges[DirectionFlag.DIR_RR];
     }
     
 	public void setFFList(VKmerListWritable forwardForwardList) {
-		this.forwardForwardList.setCopy(forwardForwardList);
+		this.edges[DirectionFlag.DIR_FF].setCopy(forwardForwardList);
 	}
 
 	public void setFRList(VKmerListWritable forwardReverseList) {
-		this.forwardReverseList.setCopy(forwardReverseList);
+		this.edges[DirectionFlag.DIR_FR].setCopy(forwardReverseList);
 	}
 
 	public void setRFList(VKmerListWritable reverseForwardList) {
-		this.reverseForwardList.setCopy(reverseForwardList);
+		this.edges[DirectionFlag.DIR_RF].setCopy(reverseForwardList);
 	}
 
 	public void setRRList(VKmerListWritable reverseReverseList) {
-		this.reverseReverseList.setCopy(reverseReverseList);
+		this.edges[DirectionFlag.DIR_RR].setCopy(reverseReverseList);
 	}
 
 	public VKmerListWritable getListFromDir(byte dir) {
@@ -198,8 +183,13 @@
 	 * Returns the length of the byte-array version of this node
 	 */
 	public int getSerializedLength() {
-	    return nodeIdList.getLength() + forwardForwardList.getLength() + forwardReverseList.getLength() + 
-	            reverseForwardList.getLength() + reverseReverseList.getLength() + kmer.getLength() + SIZE_FLOAT;
+	    int length = 0;
+	    for (byte d:DirectionFlag.values) {
+	        length += edges[d].getLength();
+	        length += threads[d].getLength();
+	    }
+	    length += kmer.getLength() + SIZE_FLOAT;
+	    return length;
 	}
 	
 	/**
@@ -214,51 +204,53 @@
     
     public void setAsCopy(byte[] data, int offset) {
         int curOffset = offset;
-        nodeIdList.set(data, curOffset);
-        
-        curOffset += nodeIdList.getLength();
-        forwardForwardList.setCopy(data, curOffset);
-        curOffset += forwardForwardList.getLength();
-        forwardReverseList.setCopy(data, curOffset);
-        curOffset += forwardReverseList.getLength();
-        reverseForwardList.setCopy(data, curOffset);
-        curOffset += reverseForwardList.getLength();
-        reverseReverseList.setCopy(data, curOffset);
-        
-        curOffset += reverseReverseList.getLength();
+        for (byte d:DirectionFlag.values) {
+            edges[d].setCopy(data, curOffset);
+            curOffset += edges[d].getLength();
+        }
+        for (byte d:DirectionFlag.values) {
+            threads[d].set(data, curOffset);
+            curOffset += threads[d].getLength();
+        }
+        startReads.set(data, curOffset);
+        curOffset += startReads.getLength();
+        endReads.set(data, curOffset);
+        curOffset += endReads.getLength();
         kmer.setAsCopy(data, curOffset);
-        
         curOffset += kmer.getLength();
         averageCoverage = Marshal.getFloat(data, curOffset);
     }
     
     public void setAsReference(byte[] data, int offset) {
         int curOffset = offset;
-        nodeIdList.setNewReference(data, curOffset);
+        for (byte d:DirectionFlag.values) {
+            edges[d].setNewReference(data, curOffset);
+            curOffset += edges[d].getLength();
+        }
+        for (byte d:DirectionFlag.values) {
+            threads[d].setNewReference(data, curOffset);
+            curOffset += threads[d].getLength();
+        }
+        startReads.setNewReference(data, curOffset);
+        curOffset += startReads.getLength();
+        endReads.setNewReference(data, curOffset);
+        curOffset += endReads.getLength();
         
-        curOffset += nodeIdList.getLength();
-        forwardForwardList.setNewReference(data, curOffset);
-        curOffset += forwardForwardList.getLength();
-        forwardReverseList.setNewReference(data, curOffset);
-        curOffset += forwardReverseList.getLength();
-        reverseForwardList.setNewReference(data, curOffset);
-        curOffset += reverseForwardList.getLength();
-        reverseReverseList.setNewReference(data, curOffset);
-        
-        curOffset += reverseReverseList.getLength();
-        kmer.setAsReference(data, curOffset);
-        
+        kmer.setAsReference(data, curOffset);        
         curOffset += kmer.getLength();
         averageCoverage = Marshal.getFloat(data, curOffset);
     }
 	
     @Override
     public void write(DataOutput out) throws IOException {
-        this.nodeIdList.write(out);
-        this.forwardForwardList.write(out);
-        this.forwardReverseList.write(out);
-        this.reverseForwardList.write(out);
-        this.reverseReverseList.write(out);
+        for (byte d:DirectionFlag.values) {
+            edges[d].write(out);
+        }
+        for (byte d:DirectionFlag.values) {
+            threads[d].write(out);
+        }
+        startReads.write(out);
+        endReads.write(out);
         this.kmer.write(out);
         out.writeFloat(averageCoverage);
     }
@@ -266,11 +258,14 @@
     @Override
     public void readFields(DataInput in) throws IOException {
         reset();
-        this.nodeIdList.readFields(in);
-        this.forwardForwardList.readFields(in);
-        this.forwardReverseList.readFields(in);
-        this.reverseForwardList.readFields(in);
-        this.reverseReverseList.readFields(in);
+        for (byte d:DirectionFlag.values) {
+            edges[d].readFields(in);
+        }
+        for (byte d:DirectionFlag.values) {
+            threads[d].readFields(in);
+        }
+        startReads.readFields(in);
+        endReads.readFields(in);
         this.kmer.readFields(in);
         averageCoverage = in.readFloat();
     }
@@ -294,49 +289,50 @@
     
     @Override
     public boolean equals(Object o) {
-        if (o instanceof NodeWritable) {
-            NodeWritable nw = (NodeWritable) o;
-            return (this.nodeIdList.equals(nw.nodeIdList)
-                    && this.forwardForwardList.equals(nw.forwardForwardList)
-                    && this.forwardReverseList.equals(nw.forwardReverseList)
-                    && this.reverseForwardList.equals(nw.reverseForwardList)
-                    && this.reverseReverseList.equals(nw.reverseReverseList) && this.kmer.equals(nw.kmer));
+        if (! (o instanceof NodeWritable))
+            return false;
+            
+        NodeWritable nw = (NodeWritable) o;
+        for (byte d:DirectionFlag.values) {
+            if (!edges[d].equals(nw.edges[d]) || !threads[d].equals(nw.threads[d]))
+                return false;
         }
-        return false;
+        return averageCoverage == nw.averageCoverage && kmer.equals(nw.kmer);
     }
     
     @Override
     public String toString() {
         StringBuilder sbuilder = new StringBuilder();
         sbuilder.append('{');
-        sbuilder.append(nodeIdList.toString()).append('\t');
-        sbuilder.append(forwardForwardList.toString()).append('\t');
-        sbuilder.append(forwardReverseList.toString()).append('\t');
-        sbuilder.append(reverseForwardList.toString()).append('\t');
-        sbuilder.append(reverseReverseList.toString()).append('\t');
+        for (byte d: DirectionFlag.values) {
+            sbuilder.append(edges[d].toString()).append('\t');
+        }
+        for (byte d: DirectionFlag.values) {
+            sbuilder.append(threads[d].toString()).append('\t');
+        }
         sbuilder.append(kmer.toString()).append('\t');
         sbuilder.append(averageCoverage).append('x').append('}');
         return sbuilder.toString();
     }
 
     public void mergeForwardNext(final NodeWritable nextNode, int initialKmerSize) {
-        this.forwardForwardList.setCopy(nextNode.forwardForwardList);
-        this.forwardReverseList.setCopy(nextNode.forwardReverseList);
+        edges[DirectionFlag.DIR_FF].setCopy(nextNode.edges[DirectionFlag.DIR_FF]);
+        edges[DirectionFlag.DIR_FR].setCopy(nextNode.edges[DirectionFlag.DIR_FR]);
         kmer.mergeWithFFKmer(initialKmerSize, nextNode.getKmer());
     }
 
     public void mergeForwardPre(final NodeWritable preNode, int initialKmerSize) {
-        this.reverseForwardList.setCopy(preNode.reverseForwardList);
-        this.reverseReverseList.setCopy(preNode.reverseReverseList);
+        edges[DirectionFlag.DIR_RF].setCopy(preNode.edges[DirectionFlag.DIR_RF]);
+        edges[DirectionFlag.DIR_RR].setCopy(preNode.edges[DirectionFlag.DIR_RR]);
         kmer.mergeWithRRKmer(initialKmerSize, preNode.getKmer());
     }
     
     public int inDegree() {
-        return reverseReverseList.getCountOfPosition() + reverseForwardList.getCountOfPosition();
+        return edges[DirectionFlag.DIR_RR].getCountOfPosition() + edges[DirectionFlag.DIR_RF].getCountOfPosition();
     }
 
     public int outDegree() {
-        return forwardForwardList.getCountOfPosition() + forwardReverseList.getCountOfPosition();
+        return edges[DirectionFlag.DIR_FF].getCountOfPosition() + edges[DirectionFlag.DIR_FR].getCountOfPosition();
     }
 
     /*
diff --git a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/AggregateKmerAggregateFactory.java b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/AggregateKmerAggregateFactory.java
index 94c8ec1..eb367a1 100644
--- a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/AggregateKmerAggregateFactory.java
+++ b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/AggregateKmerAggregateFactory.java
@@ -17,8 +17,10 @@
 
 import java.io.DataOutput;
 import java.io.IOException;
+
 import edu.uci.ics.genomix.type.KmerBytesWritable;
 import edu.uci.ics.genomix.type.NodeWritable;
+import edu.uci.ics.genomix.type.NodeWritable.DirectionFlag;
 import edu.uci.ics.hyracks.api.comm.IFrameTupleAccessor;
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
@@ -77,10 +79,9 @@
                 localUniNode.reset();
                 readNode.setAsReference(accessor.getBuffer().array(), getOffSet(accessor, tIndex, 1));
                 localUniNode.getNodeIdList().appendList(readNode.getNodeIdList());
-                localUniNode.getFFList().appendList(readNode.getFFList());
-                localUniNode.getFRList().appendList(readNode.getFRList());
-                localUniNode.getRFList().appendList(readNode.getRFList());
-                localUniNode.getRRList().appendList(readNode.getRRList());
+                for (byte d: DirectionFlag.values) {
+                    localUniNode.getListFromDir(d).appendList(readNode.getListFromDir(d));
+                }
                 localUniNode.addCoverage(readNode);
                 // make an empty field
 //                tupleBuilder.addFieldEndOffset();// mark question?
@@ -92,10 +93,9 @@
                 NodeWritable localUniNode = (NodeWritable) state.state;
                 readNode.setAsReference(accessor.getBuffer().array(), getOffSet(accessor, tIndex, 1));
                 localUniNode.getNodeIdList().appendList(readNode.getNodeIdList());
-                localUniNode.getFFList().appendList(readNode.getFFList());
-                localUniNode.getFRList().appendList(readNode.getFRList());
-                localUniNode.getRFList().appendList(readNode.getRFList());
-                localUniNode.getRRList().appendList(readNode.getRRList());
+                for (byte d: DirectionFlag.values) {
+                    localUniNode.getListFromDir(d).appendList(readNode.getListFromDir(d));
+                }
                 localUniNode.addCoverage(readNode);
             }
 
diff --git a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/MergeKmerAggregateFactory.java b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/MergeKmerAggregateFactory.java
index f83bc4b..89a0e35 100644
--- a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/MergeKmerAggregateFactory.java
+++ b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/newgraph/dataflow/aggregators/MergeKmerAggregateFactory.java
@@ -23,6 +23,7 @@
 
 import edu.uci.ics.genomix.type.KmerBytesWritable;
 import edu.uci.ics.genomix.type.NodeWritable;
+import edu.uci.ics.genomix.type.NodeWritable.DirectionFlag;
 import edu.uci.ics.hyracks.api.comm.IFrameTupleAccessor;
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
@@ -71,10 +72,9 @@
                 localUniNode.reset();
                 readNode.setAsReference(accessor.getBuffer().array(), getOffSet(accessor, tIndex, 1));
                 localUniNode.getNodeIdList().unionUpdate(readNode.getNodeIdList());
-                localUniNode.getFFList().unionUpdate(readNode.getFFList());
-                localUniNode.getFRList().unionUpdate(readNode.getFRList());
-                localUniNode.getRFList().unionUpdate(readNode.getRFList());
-                localUniNode.getRRList().unionUpdate(readNode.getRRList());
+                for (byte d: DirectionFlag.values) {
+                    localUniNode.getListFromDir(d).unionUpdate(readNode.getListFromDir(d));
+                }
                 localUniNode.addCoverage(readNode);
                 //make a fake feild to cheat caller
  //               tupleBuilder.addFieldEndOffset();
@@ -91,10 +91,9 @@
                 NodeWritable localUniNode = (NodeWritable) state.state;
                 readNode.setAsReference(accessor.getBuffer().array(), getOffSet(accessor, tIndex, 1));
                 localUniNode.getNodeIdList().unionUpdate(readNode.getNodeIdList());
-                localUniNode.getFFList().unionUpdate(readNode.getFFList());
-                localUniNode.getFRList().unionUpdate(readNode.getFRList());
-                localUniNode.getRFList().unionUpdate(readNode.getRFList());
-                localUniNode.getRRList().unionUpdate(readNode.getRRList());
+                for (byte d: DirectionFlag.values) {
+                    localUniNode.getListFromDir(d).unionUpdate(readNode.getListFromDir(d));
+                }
                 localUniNode.addCoverage(readNode);
             }
 
diff --git a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/format/InitialGraphCleanInputFormat.java b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/format/InitialGraphCleanInputFormat.java
index edb305f..5943f0a 100644
--- a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/format/InitialGraphCleanInputFormat.java
+++ b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/format/InitialGraphCleanInputFormat.java
@@ -12,6 +12,7 @@
 import edu.uci.ics.pregelix.api.util.BspUtils;
 import edu.uci.ics.genomix.type.NodeWritable;
 import edu.uci.ics.genomix.type.VKmerBytesWritable;
+import edu.uci.ics.genomix.type.NodeWritable.DirectionFlag;
 import edu.uci.ics.genomix.pregelix.io.MessageWritable;
 import edu.uci.ics.genomix.pregelix.io.VertexValueWritable;
 import edu.uci.ics.genomix.pregelix.io.VertexValueWritable.State;