diff --git a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/operator/pathmerge/P4ForPathMergeVertex.java b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/operator/pathmerge/P4ForPathMergeVertex.java
index 130d1cf..27518b4 100644
--- a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/operator/pathmerge/P4ForPathMergeVertex.java
+++ b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/operator/pathmerge/P4ForPathMergeVertex.java
@@ -12,6 +12,7 @@
 import edu.uci.ics.genomix.pregelix.client.Client;
 import edu.uci.ics.genomix.pregelix.format.NaiveAlgorithmForPathMergeInputFormat;
 import edu.uci.ics.genomix.pregelix.format.NaiveAlgorithmForPathMergeOutputFormat;
+import edu.uci.ics.genomix.pregelix.io.AdjacencyListWritable;
 import edu.uci.ics.genomix.pregelix.io.MessageWritable;
 import edu.uci.ics.genomix.pregelix.io.ValueStateWritable;
 import edu.uci.ics.genomix.pregelix.type.Message;
@@ -74,12 +75,15 @@
     private byte headFlag;
     private byte tailFlag;
     private byte outFlag;
+    private byte outUpFlag;
     
     private MessageWritable incomingMsg = new MessageWritable();
     private MessageWritable outgoingMsg = new MessageWritable();
+    private MessageWritable outgoingUpMsg = new MessageWritable();
     private PositionWritable destVertexId = new PositionWritable();
     private Iterator<PositionWritable> posIterator;
     
+    private AdjacencyListWritable neighberNode = new AdjacencyListWritable();
     /**
      * initiate kmerSize, maxIteration
      */
@@ -249,6 +253,54 @@
             //voteToHalt();
     }
     
+    /**
+     * send update message from predecessor
+     */
+    public void sendUpMsgFromPredecessor(){
+        outFlag |= MessageFlag.FROM_PREDECESSOR;
+        if(getVertexValue().getFRList().getLength() > 0){
+            outFlag |= MessageFlag.FROM_REWARDLIST;
+        }
+        outgoingMsg.setNeighberNode(getVertexValue().getIncomingList());
+        outgoingMsg.setMessage(outFlag);
+        outgoingMsg.setSourceVertexId(getVertexId());
+        sendMsg(getNextDestVertexId(getVertexValue()), outgoingMsg);
+        outUpFlag = (byte)(MessageFlag.FROM_DEADVERTEX | MessageFlag.FROM_SUCCESSOR);
+        if(getVertexValue().getRFList().getLength() > 0){
+            outUpFlag |= MessageFlag.FROM_REWARDLIST;
+            outgoingUpMsg.setNeighberNode(getVertexValue().getIncomingList());
+        } else
+            outgoingUpMsg.setNeighberNode(getVertexValue().getOutgoingList());
+        outgoingUpMsg.setMessage(outUpFlag);
+        outgoingUpMsg.setSourceVertexId(getVertexId());
+        
+        sendMsg(getPreDestVertexId(getVertexValue()), outgoingUpMsg);
+        deleteVertex(getVertexId());
+    }
+    
+    /**
+     * send update message from successor
+     */
+    public void sendUpMsgFromSuccessor(){
+        outFlag |= MessageFlag.FROM_SUCCESSOR;
+        if(getVertexValue().getRFList().getLength() > 0){
+            outFlag |= MessageFlag.FROM_REWARDLIST;
+            outgoingMsg.setNeighberNode(getVertexValue().getIncomingList());
+        } else
+            outgoingMsg.setNeighberNode(getVertexValue().getOutgoingList());
+        outgoingMsg.setMessage(outFlag);
+        outgoingMsg.setSourceVertexId(getVertexId());
+        sendMsg(getPreDestVertexId(getVertexValue()), outgoingMsg);
+        outUpFlag = (byte)(MessageFlag.FROM_DEADVERTEX | MessageFlag.FROM_PREDECESSOR);
+        if(getVertexValue().getFRList().getLength() > 0){
+            outUpFlag |= MessageFlag.FROM_REWARDLIST;
+        }
+        outgoingMsg.setNeighberNode(getVertexValue().getIncomingList());
+        outgoingUpMsg.setMessage(outUpFlag);
+        outgoingUpMsg.setSourceVertexId(getVertexId());
+        sendMsg(getNextDestVertexId(getVertexValue()), outgoingUpMsg);
+        deleteVertex(getVertexId());
+    }
     @Override
     public void compute(Iterator<MessageWritable> msgIterator) {
         initVertex();
@@ -256,7 +308,7 @@
             startSendMsg();
         else if (getSuperstep() == 2)
             initState(msgIterator);
-        else{
+        else if (getSuperstep() % 2 == 1){
             // Node may be marked as head b/c it's a real head or a real tail
             headFlag = (byte) (State.START_VERTEX & getVertexValue().getState());
             tailFlag = (byte) (State.END_VERTEX & getVertexValue().getState());
@@ -280,20 +332,10 @@
                 if (curHead) {
                     if (hasNext && !nextHead) {
                         // compress this head to the forward tail
-                        outFlag |= MessageFlag.FROM_PREDECESSOR;
-                        outgoingMsg.setMessage(outFlag);
-                        outgoingMsg.setSourceVertexId(getVertexId());
-                        destVertexId.set(getNextDestVertexId(getVertexValue()));
-                        sendMsg(destVertexId, outgoingMsg);
-                        deleteVertex(getVertexId());
+                        sendUpMsgFromPredecessor();
                     } else if (hasPrev && !prevHead) {
                         // compress this head to the reverse tail
-                        outFlag |= MessageFlag.FROM_SUCCESSOR;
-                        outgoingMsg.setMessage(outFlag);
-                        outgoingMsg.setSourceVertexId(getVertexId());
-                        destVertexId.set(getNextDestVertexId(getVertexValue()));
-                        sendMsg(destVertexId, outgoingMsg);
-                        deleteVertex(getVertexId());
+                        sendUpMsgFromSuccessor();
                     }
                 } else {
                     // I'm a tail
@@ -301,39 +343,38 @@
                         if ((!nextHead && !prevHead) && (curID.compareTo(nextID) < 0 && curID.compareTo(prevID) < 0)) {
                             // tails on both sides, and I'm the "local minimum"
                             // compress me towards the tail in forward dir
-                            outFlag |= MessageFlag.FROM_PREDECESSOR;
-                            outgoingMsg.setMessage(outFlag);
-                            outgoingMsg.setSourceVertexId(getVertexId());
-                            destVertexId.set(getNextDestVertexId(getVertexValue()));
-                            sendMsg(destVertexId, outgoingMsg);
-                            deleteVertex(getVertexId());
+                            sendUpMsgFromPredecessor();
                         }
                     } else if (!hasPrev) {
                         // no previous node
                         if (!nextHead && curID.compareTo(nextID) < 0) {
                             // merge towards tail in forward dir
-                            outFlag |= MessageFlag.FROM_PREDECESSOR;
-                            outgoingMsg.setMessage(outFlag);
-                            outgoingMsg.setSourceVertexId(getVertexId());
-                            destVertexId.set(getNextDestVertexId(getVertexValue()));
-                            sendMsg(destVertexId, outgoingMsg);
-                            deleteVertex(getVertexId());
+                            sendUpMsgFromPredecessor();
                         }
                     } else if (!hasNext) {
                         // no next node
                         if (!prevHead && curID.compareTo(prevID) < 0) {
                             // merge towards tail in reverse dir
-                            outFlag |= MessageFlag.FROM_SUCCESSOR;
-                            outgoingMsg.setMessage(outFlag);
-                            outgoingMsg.setSourceVertexId(getVertexId());
-                            destVertexId.set(getNextDestVertexId(getVertexValue()));
-                            sendMsg(destVertexId, outgoingMsg);
-                            deleteVertex(getVertexId());
+                            sendUpMsgFromSuccessor();
                         }
                     }
                 }
             }
-            
+        }
+        else if (getSuperstep() % 2 == 0){
+            while (msgIterator.hasNext()) {
+                incomingMsg = msgIterator.next();
+                outFlag = incomingMsg.getMessage();
+                if((outFlag & MessageFlag.FROM_DEADVERTEX) > 0){
+                    if((outFlag & MessageFlag.FROM_PREDECESSOR) > 0){
+                        if((outFlag & MessageFlag.FROM_REWARDLIST) > 0){
+                            
+                        } else {
+                            getVertexValue().setIncomingList(incomingMsg.getNeighberNode());
+                        }
+                    }
+                }
+            }
         }
     }
 
diff --git a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/type/MessageFlag.java b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/type/MessageFlag.java
index e83598a..de349ad 100644
--- a/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/type/MessageFlag.java
+++ b/genomix/genomix-pregelix/src/main/java/edu/uci/ics/genomix/pregelix/type/MessageFlag.java
@@ -1,28 +1,32 @@
 package edu.uci.ics.genomix.pregelix.type;
 
 public class MessageFlag {
-    public static final byte EMPTY_MESSAGE = 0;
-    public static final byte FROM_SELF = 1;
-    public static final byte FROM_SUCCESSOR = 1 << 1;
-    public static final byte FROM_PREDECESSOR = 1 << 2;
-    public static final byte IS_HEAD = 1 << 3;
-    public static final byte IS_TAIL = 1 << 4;
-
+    public static final byte FROM_SELF = 0;
+    public static final byte IS_HEAD = 1 << 1;
+    public static final byte IS_TAIL = 1 << 2;
+    public static final byte FROM_DEADVERTEX = 1 << 3;
+    //public static final byte FROM_FORWARDLIST = 1 << 4;
+    public static final byte FROM_REWARDLIST = 1 << 4;
+    public static final byte FROM_SUCCESSOR = 1 << 5;
+    public static final byte FROM_PREDECESSOR = 1 << 6;
+    
     public static String getFlagAsString(byte code) {
         // TODO: allow multiple flags to be set
         switch (code) {
-            case EMPTY_MESSAGE:
-                return "EMPTY_MESSAGE";
             case FROM_SELF:
                 return "FROM_SELF";
-            case FROM_SUCCESSOR:
-                return "FROM_SUCCESSOR";
-            case FROM_PREDECESSOR:
-                return "FROM_PREDECESSOR";
             case IS_HEAD:
                 return "IS_HEAD";
             case IS_TAIL:
                 return "IS_TAIL";
+            case FROM_DEADVERTEX:
+                return "FROM_DEADVERTEX";
+            case FROM_REWARDLIST:
+                return "FROM_REWARDLIST";
+            case FROM_SUCCESSOR:
+                return "FROM_SUCCESSOR";
+            case FROM_PREDECESSOR:
+                return "FROM_PREDECESSOR";
         }
         return "ERROR_BAD_MESSAGE";
     }