1) allow to set the maximum threshold for the liveness analysis. if threashold is...
[IRC.git] / Robust / src / Analysis / Prefetch / PrefetchAnalysis.java
index 2870afbd25b89bff68afd33c36b8e38470c361af..e8f8090be8d9e32f10c73871a25f83ce11a31d95 100644 (file)
@@ -2,7 +2,10 @@ package Analysis.Prefetch;
 
 import java.util.*;
 import Analysis.CallGraph.CallGraph;
+import Analysis.Locality.LocalityAnalysis;
 import Analysis.Prefetch.PrefetchPair;
+import Analysis.Prefetch.PairMap;
+import Analysis.Prefetch.IndexDescriptor;
 import IR.SymbolTable;
 import IR.State;
 import IR.TypeUtil;
@@ -12,210 +15,990 @@ import IR.*;
 import IR.ClassDescriptor;
 
 public class PrefetchAnalysis {
-    State state;
-    CallGraph callgraph;
-    TypeUtil typeutil;
-    Hashtable<FlatNode, Hashtable<PrefetchPair, Float>> prefetch_hash;
-
-    public PrefetchAnalysis(State state, CallGraph callgraph, TypeUtil typeutil) {
-       this.typeutil=typeutil;
-       this.state=state;
-       this.callgraph=callgraph;
-       prefetch_hash = new Hashtable();
-       DoPrefetch();
-    }
-
-    private void DoPrefetch() {
-       Iterator classit=state.getClassSymbolTable().getDescriptorsIterator();
-       while(classit.hasNext()) {
-           ClassDescriptor cn=(ClassDescriptor)classit.next();
-           doMethodAnalysis(cn);
-       }
-    }
-
-    private void doMethodAnalysis(ClassDescriptor cn) {
-           Iterator methodit=cn.getMethods();
-           while(methodit.hasNext()) {
-                   /* Classify parameters */
-                   MethodDescriptor md=(MethodDescriptor)methodit.next();
-                   FlatMethod fm=state.getMethodFlat(md);
-                   doFlatNodeAnalysis(fm);
-           }
-    }
-
-    private void doFlatNodeAnalysis(FlatMethod fm) {
-           Set<FlatNode> tovisit = fm.getNodeSet(); //Flat nodes to process
-           tovisit.add(fm);
-           while(!tovisit.isEmpty()) {
-                   Hashtable<PrefetchPair, Float> nodehash = new Hashtable();
-                   FlatNode fn = (FlatNode)tovisit.iterator().next();
-                   tovisit.remove(fn);
-                   //System.out.println("DEBUG -> kind = " + fn.kind());
-                   // Do self node prefetch
-                   doNodePrefetch(fn);
-                   // Do the child node analysis
-                   boolean curr_modified = doNodeChildPrefetch(fn);
-           }
-    }
-
-    private void doNodePrefetch(FlatNode fn) {
-           Hashtable<PrefetchPair, Float> nodehash = new Hashtable();
-           switch(fn.kind()) {
-                   case FKind.FlatFieldNode:
-                           FlatFieldNode currffn = (FlatFieldNode) fn;
-                           System.out.print("DEBUG -> is an object\t");
-                           System.out.println(currffn.toString());
-                           FieldDescriptor currffn_field =  currffn.getField();
-                           TempDescriptor currffn_src = currffn.getSrc();
-                           if (currffn_field.getType().isPtr()) {
-                                   System.out.println("\t pointer " + currffn_field.toString());
-                                   PrefetchPair pp = new PrefetchPair(currffn_src, (Descriptor) currffn_field, false);
-                                   Float prob = new Float((double)1.0);
-                                   nodehash.put(pp, prob);
-                                   prefetch_hash.put(fn, nodehash);
-                           }
-                           break;
-                   case FKind.FlatElementNode:
-                           FlatElementNode currfen = (FlatElementNode) fn;
-                           TempDescriptor currfen_index = currfen.getIndex();
-                           TempDescriptor currfen_src = currfen.getSrc();
-                           System.out.print("DEBUG -> is an array\t");
-                           System.out.println(currfen.toString());
-                           PrefetchPair pp = new PrefetchPair(currfen_src, (Descriptor) currfen_index, true);
-                           Float prob = new Float((double)1.0);
-                           nodehash.put(pp, prob);
-                           prefetch_hash.put(fn, nodehash);
-                           break;
-                   default:
-                           break;
-           }
-    }
-
-    private boolean doNodeChildPrefetch(FlatNode curr) {
-           boolean isCurrMod = false;
-
-           for (int i = 0; i < curr.numNext(); i++) {
-                   FlatNode child_node = curr.getNext(i);
-                   if (prefetch_hash.containsKey(child_node)) {
-                           Hashtable<PrefetchPair, Float> child_hash = prefetch_hash.get(child_node);
-                           switch(curr.kind()) {
-                                   case FKind.FlatFieldNode:
-                                           break;
-                                   case FKind.FlatElementNode:
-                                           break;
-                                   default:
-                                           if (prefetch_hash.containsKey(curr)) {
-                                                   isCurrMod = true;
-                                                   Hashtable<PrefetchPair, Float> parentcopy = prefetch_hash.get(curr);
-                                                   Hashtable<PrefetchPair, Float> tocompare = new Hashtable<PrefetchPair, Float>();
-                                                   Enumeration e = parentcopy.keys();
-                                                   while (e.hasMoreElements()) {
-                                                           PrefetchPair pp = (PrefetchPair) e.nextElement();
-                                                           if (child_hash.contains(pp)) {
-                                                                   Float cprob = child_hash.get(pp);
-                                                                   Float fprob = parentcopy.get(pp);
-                                                                   // TODO fix this
-                                                                   Float newprob = cprob.floatValue() * fprob.floatValue();
-                                                                   tocompare.put(pp, newprob);
-                                                                   child_hash.remove(pp);
-                                                           } else {
-                                                                   tocompare.put(pp, parentcopy.get(pp));
-                                                           }
-                                                   }
-                                                   e = child_hash.keys();
-                                                   while (e.hasMoreElements()) {
-                                                           tocompare.put((PrefetchPair) e.nextElement(), child_hash.get((PrefetchPair) e.nextElement()));
-                                                   }
-                                           } else {
-                                                   prefetch_hash.put(curr, child_hash);
-                                           }
-                           }
-                   } 
-           }
-           return isCurrMod;
-    }
-
-    private void doAnalysis() {
-       Iterator classit=state.getClassSymbolTable().getDescriptorsIterator();
-       while(classit.hasNext()) {
-           ClassDescriptor cn=(ClassDescriptor)classit.next();
-           Iterator methodit=cn.getMethods();
-           while(methodit.hasNext()) {
-               /* Classify parameters */
-               MethodDescriptor md=(MethodDescriptor)methodit.next();
-               FlatMethod fm=state.getMethodFlat(md);
-               System.out.println("DEBUG -> ");
-               printMethod(fm);
-           }
-       }
-    }
-
-    private void printMethod(FlatMethod fm) {
-       System.out.println(fm.getMethod()+" {");
-        HashSet tovisit=new HashSet();
-        HashSet visited=new HashSet();
-        int labelindex=0;
-        Hashtable nodetolabel=new Hashtable();
-        tovisit.add(fm);
-        FlatNode current_node=null;
-        //Assign labels 1st
-        //Node needs a label if it is
-        while(!tovisit.isEmpty()) {
-            FlatNode fn=(FlatNode)tovisit.iterator().next();
-            tovisit.remove(fn);
-            visited.add(fn);
-           System.out.println("DEBUG -> " + fn.kind());
-
-            for(int i=0;i<fn.numNext();i++) {
-                FlatNode nn=fn.getNext(i);
-                if(i>0) {
-                    //1) Edge >1 of node
-                    nodetolabel.put(nn,new Integer(labelindex++));
-                }
-                if (!visited.contains(nn)&&!tovisit.contains(nn)) {
-                    tovisit.add(nn);
+  State state;
+  CallGraph callgraph;
+  TypeUtil typeutil;
+  LoopExit loop;
+
+  Set<FlatNode> tovisit;
+  public Hashtable<FlatNode, Hashtable<PrefetchPair, Double>> prefetch_hash;  //holds all flatnodes and corresponding prefetch set
+  public Hashtable<FlatNode, Hashtable<FlatNode, PairMap>> pmap_hash;  //holds all flatnodes and mappings between child prefetch pair and parent prefetch pair
+  public static final double PROB_DIFF = 0.05;          //threshold for difference in probabilities during first phase of analysis
+  public static final double ANALYSIS_THRESHOLD_PROB = 0.10;   //threshold for prefetches to stop propagating during first phase of analysis
+  public static final double PREFETCH_THRESHOLD_PROB = 0.30;  //threshold for prefetches to stop propagating while applying prefetch rules during second phase of analysis
+  public static int prefetchsiteid = 1;   //initialized to one because there is a prefetch siteid 0 for starting remote thread
+  LocalityAnalysis locality;
+
+  public PrefetchAnalysis(State state, CallGraph callgraph, TypeUtil typeutil, LocalityAnalysis locality) {
+    this.typeutil=typeutil;
+    this.state=state;
+    this.callgraph=callgraph;
+    this.locality=locality;
+    prefetch_hash = new Hashtable<FlatNode, Hashtable<PrefetchPair,Double>>();
+    pmap_hash = new Hashtable<FlatNode, Hashtable<FlatNode, PairMap>>();
+    this.loop=new LoopExit(state);
+    DoPrefetch();
+  }
+
+
+  /** This function starts the prefetch analysis */
+  private void DoPrefetch() {
+    for (Iterator methodit=locality.getMethods().iterator(); methodit.hasNext(); ) {
+      MethodDescriptor md=(MethodDescriptor)methodit.next();
+      if (state.excprefetch.contains(md.getClassMethodName()))
+        continue;         //Skip this method
+      Hashtable<FlatNode, HashSet<PrefetchPair>> newprefetchset = new Hashtable<FlatNode, HashSet<PrefetchPair>>();
+      FlatMethod fm=state.getMethodFlat(md);
+      doFlatNodeAnalysis(fm);
+      doInsPrefetchAnalysis(fm, newprefetchset);
+      if(newprefetchset.size() > 0) {
+        addFlatPrefetchNode(newprefetchset);
+      }
+      newprefetchset = null;
+    }
+  }
+
+  /** This function calls analysis for every node in a method */
+  private void doFlatNodeAnalysis(FlatMethod fm) {
+    tovisit = fm.getNodeSet();
+    Hashtable<PrefetchPair, Double> nodehash = new Hashtable<PrefetchPair, Double>();
+    /* Create Empty Prefetch Sets for all flat nodes in the global hashtable */
+    while(!tovisit.isEmpty()) {
+      FlatNode fn = (FlatNode)tovisit.iterator().next();
+      prefetch_hash.put(fn, nodehash);
+      tovisit.remove(fn);
+    }
+
+    /* Visit and process nodes */
+    tovisit = fm.getNodeSet();
+    while(!tovisit.isEmpty()) {
+      FlatNode fn = (FlatNode)tovisit.iterator().next();
+      tovisit.remove(fn);
+
+      doChildNodeAnalysis(fm.getMethod(),fn);
+    }
+  }
+
+  /**
+   * This function generates the prefetch sets for a given Flatnode considering the kind of node
+   * It calls severals functions based on the kind of the node and
+   * returns true: if the prefetch set has changed since last time the node was analysed
+   * returns false : otherwise
+   */
+  private void doChildNodeAnalysis(MethodDescriptor md, FlatNode curr) {
+    if (curr.kind()==FKind.FlatCondBranch) {
+      processFlatCondBranch((FlatCondBranch)curr, md);
+    } else {
+      Hashtable<PrefetchPair, Double> child_prefetch_set_copy = new Hashtable<PrefetchPair, Double>();
+      if(curr.numNext() != 0) {
+        FlatNode child_node = curr.getNext(0);
+        if(prefetch_hash.containsKey(child_node)) {
+          child_prefetch_set_copy = (Hashtable<PrefetchPair,Double>)prefetch_hash.get(child_node).clone();
+        }
+
+      }
+      switch(curr.kind()) {
+      case FKind.FlatCall:
+        processCall((FlatCall)curr,child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatBackEdge:
+      case FKind.FlatCheckNode:
+      case FKind.FlatReturnNode:
+      case FKind.FlatAtomicEnterNode:
+      case FKind.FlatAtomicExitNode:
+      case FKind.FlatFlagActionNode:
+      case FKind.FlatGlobalConvNode:
+      case FKind.FlatNop:
+      case FKind.FlatExit:
+      case FKind.FlatNew:
+      case FKind.FlatCastNode:
+      case FKind.FlatTagDeclaration:
+      case FKind.FlatInstanceOfNode:
+        processDefaultCase(curr,child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatMethod:
+        //TODO change it to take care of FlatMethod, Flatcalls
+        processFlatMethod(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatFieldNode:
+        processFlatFieldNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatElementNode:
+        processFlatElementNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatOpNode:
+        processFlatOpNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatLiteralNode:
+        processFlatLiteralNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatSetElementNode:
+        processFlatSetElementNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatSetFieldNode:
+        processFlatSetFieldNode(curr, child_prefetch_set_copy);
+        break;
+
+      case FKind.FlatOffsetNode:
+        processDefaultCase(curr,child_prefetch_set_copy);
+        break;
+
+      default:
+        throw new Error("No such Flatnode kind");
+      }
+    }
+  }
+
+  /**This function compares all the prefetch pairs in a Prefetch set hashtable and
+   * returns: true if something has changed in the new Prefetch set else
+   * returns: false
+   */
+  private boolean comparePrefetchSets(Hashtable<PrefetchPair, Double> oldPrefetchSet, Hashtable<PrefetchPair, Double> newPrefetchSet) {
+    if (oldPrefetchSet.size()!=newPrefetchSet.size())
+      return true;
+
+    for(Enumeration e = newPrefetchSet.keys(); e.hasMoreElements(); ) {
+      PrefetchPair pp = (PrefetchPair) e.nextElement();
+      double newprob = newPrefetchSet.get(pp).doubleValue();
+      if (!oldPrefetchSet.containsKey(pp))
+        return true;
+      double oldprob = oldPrefetchSet.get(pp).doubleValue();
+
+      if((newprob - oldprob) > PROB_DIFF) {
+        return true;
+      }
+      if (newprob >= PREFETCH_THRESHOLD_PROB && oldprob < PREFETCH_THRESHOLD_PROB) {
+        return true;
+      }
+      if (oldprob>newprob) {
+        System.out.println("ERROR:" + pp);
+        System.out.println(oldprob + " -> "+ newprob);
+      }
+    }
+    return false;
+  }
+
+  private void updatePairMap(FlatNode curr, PairMap pm, int index) {
+    if (index>=curr.numNext())
+      return;
+    if (!pmap_hash.containsKey(curr.getNext(index))) {
+      pmap_hash.put(curr.getNext(index), new Hashtable<FlatNode, PairMap>());
+    }
+    pmap_hash.get(curr.getNext(index)).put(curr, pm);
+  }
+
+  private void updatePrefetchSet(FlatNode curr, Hashtable<PrefetchPair, Double> newset) {
+    Hashtable<PrefetchPair, Double>oldset=prefetch_hash.get(curr);
+    if (comparePrefetchSets(oldset, newset)) {
+      for(int i=0; i<curr.numPrev(); i++) {
+        tovisit.add(curr.getPrev(i));
+      }
+      prefetch_hash.put(curr, newset);
+    }
+  }
+
+
+  /** This function processes the prefetch set of FlatFieldNode
+   * It generates a new prefetch set after comparision with its children
+   * Then compares it with its old prefetch set
+   * If old prefetch set is not same as new prefetch set then enqueue the parents
+   * of the current FlatFieldNode
+   * */
+  private void processFlatFieldNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    Hashtable<PrefetchPair, Double> currcopy = new Hashtable<PrefetchPair, Double>();
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatFieldNode currffn = (FlatFieldNode) curr;
+    PairMap pm = new PairMap();
+
+    /* Do Self analysis of the current node*/
+    FieldDescriptor currffn_field =  currffn.getField();
+    TempDescriptor currffn_src = currffn.getSrc();
+    if (currffn_field.getType().isPtr()) {
+      PrefetchPair pp = new PrefetchPair(currffn_src, (Descriptor) currffn_field);
+      Double prob = new Double(1.0);
+      tocompare.put(pp, prob);
+    }
+
+    /* Get each prefetch pair of the child and match it with the destination temp descriptor of curr FlatFieldNode */
+
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      if (childpp.base == currffn.getDst() && (childpp.getDesc()!= null)) {
+        if (currffn.getField().getType().isPtr()) {
+          ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+          newdesc.add(currffn.getField());
+          newdesc.addAll(childpp.desc);
+          PrefetchPair newpp =  new PrefetchPair(currffn.getSrc(), newdesc);
+          Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+          if (tocompare.containsKey(newpp)) {
+            Double oldprob=tocompare.get(newpp);
+            newprob=1.0-(1.0-oldprob)*(1.0-newprob);
+          }
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+        }
+        //drop if not ptr
+      } else if(childpp.base == currffn.getDst() && (childpp.getDesc() == null)) {
+        //covered by current prefetch
+        child_prefetch_set_copy.remove(childpp);
+      } else if(childpp.containsTemp(currffn.getDst())) {
+        child_prefetch_set_copy.remove(childpp);
+      } else {
+        Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+        if (tocompare.containsKey(childpp)) {
+          Double oldprob=tocompare.get(childpp);
+          newprob=1.0-(1.0-oldprob)*(1.0-newprob);
+        }
+        tocompare.put(childpp, newprob);
+        pm.addPair(childpp, childpp);
+      }
+    }
+
+    for(Iterator<PrefetchPair> it=tocompare.keySet().iterator(); it.hasNext(); ) {
+      PrefetchPair pp=it.next();
+      if (tocompare.get(pp)<ANALYSIS_THRESHOLD_PROB)
+        it.remove();
+
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function processes the prefetch set of a FlatElementNode
+   * It generates a new prefetch set after comparision with its children
+   * It compares the old prefetch set with this new prefetch set and enqueues the parents
+   * of the current node if change occurs and updates the global flatnode hash table
+   * */
+  private void processFlatElementNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+
+    Hashtable<PrefetchPair, Double> currcopy = new Hashtable<PrefetchPair, Double>();
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatElementNode currfen = (FlatElementNode) curr;
+    PairMap pm = new PairMap();
+
+
+    /* Do Self analysis of the current node*/
+    TempDescriptor currfen_index = currfen.getIndex();
+    IndexDescriptor idesc = new IndexDescriptor(currfen_index, 0);
+    TempDescriptor currfen_src = currfen.getSrc();
+    if(currfen.getDst().getType().isPtr()) {
+      PrefetchPair pp = new PrefetchPair(currfen_src, (Descriptor) idesc);
+      Double prob = new Double(1.0);
+      currcopy.put(pp, prob);
+    }
+
+    /* Get each prefetch pair of the child and match it with the destination temp descriptor of curr FlatFieldNode */
+    PrefetchPair currpp = null;
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      if (childpp.base == currfen.getDst() && (childpp.getDesc()!= null)) {
+        if (currfen.getDst().getType().isPtr()) {
+          ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+          newdesc.add((Descriptor)idesc);
+          newdesc.addAll(childpp.desc);
+          PrefetchPair newpp =  new PrefetchPair(currfen.getSrc(), newdesc);
+          Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+          child_prefetch_set_copy.remove(childpp);
+          /* Check for independence of prefetch pairs to compute new probability */
+          if(child_prefetch_set_copy.containsKey(newpp)) {
+            newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+            if(newprob < ANALYSIS_THRESHOLD_PROB) {
+              tocompare.remove(newpp);
+            } else {
+              tocompare.put(newpp, newprob);
+              pm.addPair(newpp, newpp);
+            }
+            child_prefetch_set_copy.remove(newpp);
+          }
+        }
+      } else if(childpp.base == currfen.getDst() && (childpp.getDesc() == null)) {
+        child_prefetch_set_copy.remove(childpp);
+      } else if(childpp.containsTemp(currfen.getDst())) {
+        child_prefetch_set_copy.remove(childpp);
+      } else {
+        continue;
+      }
+    }
+    /* Check if curr prefetch set and the child prefetch set have same prefetch pairs
+     * if so calculate the new probability */
+    for(Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      for(Enumeration e = currcopy.keys(); e.hasMoreElements(); ) {
+        currpp = (PrefetchPair) e.nextElement();
+        if(currpp.equals(childpp)) {
+          pm.addPair(childpp, currpp);
+          child_prefetch_set_copy.remove(childpp);
+          break;
+        }
+      }
+    }
+
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+      child_prefetch_set_copy.remove(childpp);
+    }
+
+    /* Merge curr prefetch pairs */
+    for (Enumeration e = currcopy.keys(); e.hasMoreElements(); ) {
+      currpp = (PrefetchPair) e.nextElement();
+      tocompare.put(currpp, currcopy.get(currpp).doubleValue());
+      currcopy.remove(currpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function processes the prefetch set of a FlatSetFieldNode
+   * It generates a new prefetch set after comparision with its children
+   * It compares the old prefetch set with this new prefetch set and enqueues the parents
+   * of the current node if change occurs and then updates the global flatnode hash table
+   * */
+  private void processFlatSetFieldNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatSetFieldNode currfsfn = (FlatSetFieldNode) curr;
+    PairMap pm = new PairMap();
+
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      if(childpp.base == currfsfn.getDst()) {
+        int size = childpp.desc.size();
+        if(size >=2) {         /*e.g. x.f = g (with child prefetches x.f.g, x.f[0].j) */
+          if((childpp.getDescAt(0) instanceof FieldDescriptor) && (childpp.getDescAt(0) == currfsfn.getField())) {
+            ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+            for(int i = 0; i<(childpp.desc.size()-1); i++) {
+              newdesc.add(i,childpp.desc.get(i+1));
+            }
+            PrefetchPair newpp =  new PrefetchPair(currfsfn.getSrc(), newdesc);
+            Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+            tocompare.put(newpp, newprob);
+            pm.addPair(childpp, newpp);
+            child_prefetch_set_copy.remove(childpp);
+            /* Check for independence of prefetch pairs in newly generated prefetch pair
+             * to compute new probability */
+            if(child_prefetch_set_copy.containsKey(newpp)) {
+              newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+              if(newprob < ANALYSIS_THRESHOLD_PROB) {
+                tocompare.remove(newpp);
+              } else {
+                tocompare.put(newpp, newprob);
+                pm.addPair(newpp, newpp);
+              }
+              child_prefetch_set_copy.remove(newpp);
+            }
+          }
+        } else if(size==1) {         /* e.g x.f = g (with child prefetch x.f) */
+          if((childpp.getDescAt(0) instanceof FieldDescriptor) && (childpp.getDescAt(0) == currfsfn.getField())) {
+            child_prefetch_set_copy.remove(childpp);
+          }
+        } else {
+          continue;
+        }
+      }
+    }
+
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+      child_prefetch_set_copy.remove(childpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function processes the prefetch set of a FlatSetElementNode
+   * It generates a new prefetch set after comparision with its children
+   * It compares the old prefetch set with this new prefetch set and enqueues the parents
+   * of the current node if change occurs and then updates the global flatnode hash table
+   * */
+  private void processFlatSetElementNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatSetElementNode currfsen = (FlatSetElementNode) curr;
+    PairMap pm = new PairMap();
+
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      if (childpp.base == currfsen.getDst()) {
+        int sizedesc = childpp.desc.size();
+        if((childpp.getDescAt(0) instanceof IndexDescriptor)) {
+          int sizetempdesc = ((IndexDescriptor)(childpp.getDescAt(0))).tddesc.size();
+          if(sizetempdesc == 1) {
+            if((((IndexDescriptor)childpp.getDescAt(0)).tddesc.get(0) == currfsen.getIndex()) && (sizedesc>=2)) {
+              /* For e.g. a[i] = g with child prefetch set a[i].r or a[i].r.f */
+              ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+              for(int i = 0; i<(childpp.desc.size()-1); i++) {
+                newdesc.add(i,childpp.desc.get(i+1));
+              }
+              PrefetchPair newpp =  new PrefetchPair(currfsen.getSrc(), newdesc);
+              Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+              tocompare.put(newpp, newprob);
+              pm.addPair(childpp, newpp);
+              child_prefetch_set_copy.remove(childpp);
+              /* Check for independence of prefetch pairs to compute new probability */
+              if(child_prefetch_set_copy.containsKey(newpp)) {
+                newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+                if(newprob < ANALYSIS_THRESHOLD_PROB) {
+                  tocompare.remove(newpp);
                 } else {
-                    //2) Join point
-                    nodetolabel.put(nn,new Integer(labelindex++));
+                  tocompare.put(newpp, newprob);
+                  pm.addPair(newpp, newpp);
                 }
+                child_prefetch_set_copy.remove(newpp);
+              }
+            } else if((((IndexDescriptor)childpp.getDescAt(0)).tddesc.get(0) == currfsen.getIndex()) && (sizedesc==1))
+              /* For e.g. a[i] = g with child prefetch set a[i] */
+              child_prefetch_set_copy.remove(childpp);
+          } else {
+            continue;
+          }
+        }
+      }
+    }
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+      child_prefetch_set_copy.remove(childpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function applies rules and does analysis for a FlatOpNode
+   *  And updates the global prefetch hashtable
+   * */
+  private void processFlatOpNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    int index;
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatOpNode currfopn = (FlatOpNode) curr;
+    PairMap pm = new PairMap();
+
+    if(currfopn.getOp().getOp() == Operation.ASSIGN) {
+      for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+        PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+        PrefetchPair copyofchildpp = (PrefetchPair) childpp.clone();
+
+        /* For cases like x=y  with child prefetch set x[i].z,x.g*/
+        if(childpp.base == currfopn.getDest()) {
+          ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+          newdesc.addAll(childpp.desc);
+          PrefetchPair newpp =  new PrefetchPair(currfopn.getLeft(), newdesc);
+          Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+          child_prefetch_set_copy.remove(childpp);
+          /* Check for independence of prefetch pairs to compute new probability */
+          if(child_prefetch_set_copy.containsKey(newpp)) {
+            newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+            if(newprob < ANALYSIS_THRESHOLD_PROB) {
+              tocompare.remove(newpp);
+            } else {
+              tocompare.put(newpp, newprob);
+              pm.addPair(newpp, newpp);
+            }
+            child_prefetch_set_copy.remove(newpp);
+          }
+          /* For cases like x=y  with child prefetch set r[x].p, r[p+x].q where x is a  tempdescriptor*/
+        } else if(copyofchildpp.containsTemp(currfopn.getDest())) {
+          PrefetchPair newpp=copyofchildpp.replaceTemp(currfopn.getDest(), new TempDescriptor[] {currfopn.getLeft()});
+          Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+          child_prefetch_set_copy.remove(childpp);
+          /* Check for independence of prefetch pairs to compute new probability*/
+          if(child_prefetch_set_copy.containsKey(newpp)) {
+            newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+            if(newprob < ANALYSIS_THRESHOLD_PROB) {
+              tocompare.remove(newpp);
+            } else {
+              tocompare.put(newpp, newprob);
+              pm.addPair(newpp, newpp);
+            }
+            child_prefetch_set_copy.remove(newpp);
+          }
+          newpp = null;
+        } else {
+          continue;
+        }
+      }
+      //case i = i+z with child prefetch set a[i].x
+    } else if(currfopn.getRight()!=null && (currfopn.getOp().getOp() == Operation.ADD)) {
+      for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+        PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+        PrefetchPair copyofchildpp = (PrefetchPair) childpp.clone();
+
+        if(copyofchildpp.containsTemp(currfopn.getDest())) {
+          PrefetchPair newpp=copyofchildpp.replaceTemp(currfopn.getDest(), new TempDescriptor[] {currfopn.getLeft(), currfopn.getRight()});
+          Double newprob = child_prefetch_set_copy.get(childpp).doubleValue();
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+          child_prefetch_set_copy.remove(childpp);
+          /* Check for independence of prefetch pairs to compute new probability*/
+          if(child_prefetch_set_copy.containsKey(newpp)) {
+            newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+            if(newprob < ANALYSIS_THRESHOLD_PROB) {
+              tocompare.remove(newpp);
+            } else {
+              tocompare.put(newpp, newprob);
+              pm.addPair(newpp, newpp);
             }
+            child_prefetch_set_copy.remove(newpp);
+          }
+        } else {
+          continue;
+        }
+      }
+    } else if(currfopn.getRight()!=null && (currfopn.getOp().getOp() == Operation.SUB)) {
+      for(Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+        PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+        if(childpp.containsTemp(currfopn.getDest())) {
+          child_prefetch_set_copy.remove(childpp);
         }
-        //Do the actual printing
-        tovisit=new HashSet();
-        visited=new HashSet();
-        tovisit.add(fm);
-        while(current_node!=null||!tovisit.isEmpty()) {
-            if (current_node==null) {
-                current_node=(FlatNode)tovisit.iterator().next();
-                tovisit.remove(current_node);
+      }
+    } else {
+      //FIXME Is not taken care of for cases like x = -y followed by a[x].i
+    }
+
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+      child_prefetch_set_copy.remove(childpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function processes a FlatLiteralNode where cases such as
+   * for e.g. i = 0 with child prefetch sets a[i].r, a[j+i].r or a[j].b[i].r
+   * are handled */
+  private void processFlatLiteralNode(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatLiteralNode currfln = (FlatLiteralNode) curr;
+    PairMap pm = new PairMap();
+
+    if(currfln.getType().isIntegerType()) {
+      for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+        PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+        PrefetchPair copyofchildpp = (PrefetchPair) childpp.clone();
+        if(copyofchildpp.containsTemp(currfln.getDst())) {
+          ArrayList<Descriptor> copychilddesc = (ArrayList<Descriptor>)copyofchildpp.getDesc();
+          int sizetempdesc = copychilddesc.size();
+          for(ListIterator it = copychilddesc.listIterator(); it.hasNext(); ) {
+            Object o = it.next();
+            if(o instanceof IndexDescriptor) {
+              ArrayList<TempDescriptor> td = (ArrayList<TempDescriptor>)((IndexDescriptor)o).tddesc;
+              int sizetddesc = td.size();
+              if(td.contains(currfln.getDst())) {
+                int index = td.indexOf(currfln.getDst());
+                td.remove(index);
+                ((IndexDescriptor)o).offset += (Integer)currfln.getValue();
+              }
+            }
+          }
+          ArrayList<Descriptor> newdesc = new ArrayList<Descriptor>();
+          newdesc.addAll(copychilddesc);
+          PrefetchPair newpp =  new PrefetchPair(childpp.base, newdesc);
+          Double newprob = (child_prefetch_set_copy.get(childpp)).doubleValue();
+          tocompare.put(newpp, newprob);
+          pm.addPair(childpp, newpp);
+          child_prefetch_set_copy.remove(childpp);
+          /* Check for independence of prefetch pairs to compute new probability */
+          if(child_prefetch_set_copy.containsKey(newpp)) {
+            newprob = (1.0 - ((1.0 - child_prefetch_set_copy.get(newpp).doubleValue()) * (1.0 - tocompare.get(newpp).doubleValue())));
+            if(newprob < ANALYSIS_THRESHOLD_PROB) {
+              tocompare.remove(newpp);
+            } else {
+              tocompare.put(newpp, newprob);
+              pm.addPair(newpp, newpp);
             }
-            visited.add(current_node);
-            if (nodetolabel.containsKey(current_node))
-                System.out.println("L"+nodetolabel.get(current_node)+":");
-            if (current_node.numNext()==0) {
-               System.out.println("   "+current_node.toString());
-               current_node=null;
-            } else if(current_node.numNext()==1) {
-               System.out.println("   "+current_node.toString());
-                FlatNode nextnode=current_node.getNext(0);
-                if (visited.contains(nextnode)) {
-                    System.out.println("goto L"+nodetolabel.get(nextnode));
-                    current_node=null;
-                } else
-                    current_node=nextnode;
-            } else if (current_node.numNext()==2) {
-                /* Branch */
-                System.out.println("   "+((FlatCondBranch)current_node).toString("L"+nodetolabel.get(current_node.getNext(1))));
-                if (!visited.contains(current_node.getNext(1)))
-                    tovisit.add(current_node.getNext(1));
-                if (visited.contains(current_node.getNext(0))) {
-                    System.out.println("goto L"+nodetolabel.get(current_node.getNext(0)));
-                    current_node=null;
-                } else
-                    current_node=current_node.getNext(0);
-            } else throw new Error();
-        }
-        System.out.println("}");
+            child_prefetch_set_copy.remove(newpp);
+          }
+        }
+      }
+    }
+
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+      child_prefetch_set_copy.remove(childpp);
     }
 
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function processes a FlatMethod where the method propagates
+   * the entire prefetch set of its child node */
+  private void processFlatMethod(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+    FlatMethod currfm = (FlatMethod) curr;
+    PairMap pm = new PairMap();
+
+    /* Merge child prefetch pairs */
+    for (Enumeration ecld = child_prefetch_set_copy.keys(); ecld.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) ecld.nextElement();
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp).doubleValue());
+      pm.addPair(childpp, childpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function handles the processes the FlatNode of type FlatCondBranch
+   * It combines prefetches of both child elements and create a new hash table called
+   * branch_prefetch_set to contains the entries of both its children
+   */
+  private void processFlatCondBranch(FlatCondBranch fcb, MethodDescriptor md) {
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();    //temporary hash table
+    PairMap truepm = new PairMap();
+    PairMap falsepm = new PairMap();
+    Hashtable<PrefetchPair, Double> truechild=prefetch_hash.get(fcb.getNext(0));
+    Hashtable<PrefetchPair, Double> falsechild=prefetch_hash.get(fcb.getNext(1));
+
+    HashSet<PrefetchPair> allpp=new HashSet<PrefetchPair>();
+    allpp.addAll(truechild.keySet());
+    allpp.addAll(falsechild.keySet());
+
+    for(Iterator<PrefetchPair> ppit=allpp.iterator(); ppit.hasNext(); ) {
+      PrefetchPair pp=ppit.next();
+      double trueprob=0,falseprob=0;
+      if (truechild.containsKey(pp))
+        trueprob=truechild.get(pp).doubleValue();
+      if (falsechild.containsKey(pp))
+        falseprob=falsechild.get(pp).doubleValue();
+
+      double newprob=trueprob*fcb.getTrueProb()+falseprob*fcb.getFalseProb();
+      if (loop.isLoopingBranch(md,fcb)&&
+          newprob<falseprob) {
+        newprob=falseprob;
+      }
+
+      if(newprob < ANALYSIS_THRESHOLD_PROB)       //Skip pp that are below threshold
+        continue;
+
+      tocompare.put(pp, newprob);
+      if (truechild.containsKey(pp))
+        truepm.addPair(pp, pp);
+
+      if (falsechild.containsKey(pp))
+        falsepm.addPair(pp, pp);
+
+    }
+
+    updatePairMap(fcb, truepm, 0);
+    updatePairMap(fcb, falsepm, 1);
+    updatePrefetchSet(fcb, tocompare);
+  }
+
+  /** If FlatNode is not concerned with the prefetch set of its Child then propagate
+   * prefetches up the FlatNode*/
+  private void processDefaultCase(FlatNode curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    PairMap pm = new PairMap();
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+
+    /* Propagate all child nodes */
+nexttemp:
+    for(Enumeration e = child_prefetch_set_copy.keys(); e.hasMoreElements(); ) {
+      PrefetchPair childpp = (PrefetchPair) e.nextElement();
+      TempDescriptor[] writearray=curr.writesTemps();
+      for(int i=0; i<writearray.length; i++) {
+        TempDescriptor wtd=writearray[i];
+        if(childpp.base == wtd||
+           childpp.containsTemp(wtd))
+          continue nexttemp;
+      }
+      tocompare.put(childpp, child_prefetch_set_copy.get(childpp));
+      pm.addPair(childpp, childpp);
+    }
+
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** If FlatNode is not concerned with the prefetch set of its Child then propagate
+   * prefetches up the FlatNode*/
+  private void processCall(FlatCall curr, Hashtable<PrefetchPair, Double> child_prefetch_set_copy) {
+    PairMap pm = new PairMap();
+    Hashtable<PrefetchPair, Double> tocompare = new Hashtable<PrefetchPair, Double>();
+
+    /* Don't propagate prefetches across cache clear */
+    if (!(curr.getMethod().getClassMethodName().equals("System.clearPrefetchCache")||
+          curr.getMethod().getClassMethodName().equals("Barrier.enterBarrier"))) {
+      /* Propagate all child nodes */
+nexttemp:
+      for(Enumeration e = child_prefetch_set_copy.keys(); e.hasMoreElements(); ) {
+        PrefetchPair childpp = (PrefetchPair) e.nextElement();
+        TempDescriptor[] writearray=curr.writesTemps();
+        for(int i=0; i<writearray.length; i++) {
+          TempDescriptor wtd=writearray[i];
+          if(childpp.base == wtd||
+             childpp.containsTemp(wtd))
+            continue nexttemp;
+        }
+        tocompare.put(childpp, child_prefetch_set_copy.get(childpp));
+        pm.addPair(childpp, childpp);
+      }
+
+    }
+    updatePairMap(curr, pm, 0);
+    updatePrefetchSet(curr, tocompare);
+  }
+
+  /** This function prints the Prefetch pairs of a given flatnode */
+  private void printPrefetchPairs(FlatNode fn) {
+    System.out.println(fn);
+    if(prefetch_hash.containsKey(fn)) {
+      System.out.print("Prefetch" + "(");
+      Hashtable<PrefetchPair, Double> currhash = (Hashtable) prefetch_hash.get(fn);
+      for(Enumeration pphash= currhash.keys(); pphash.hasMoreElements(); ) {
+        PrefetchPair pp = (PrefetchPair) pphash.nextElement();
+        double v=currhash.get(pp).doubleValue();
+        if (v>.2)
+          System.out.print(pp.toString() +"-"+v + ", ");
+      }
+      System.out.println(")");
+    } else {
+      System.out.println("Flatnode is currently not present in the global hash: Prefetch Set is Empty");
+    }
+  }
+
+  private void doInsPrefetchAnalysis(FlatMethod fm, Hashtable<FlatNode, HashSet<PrefetchPair>> newprefetchset) {
+    Hashtable<FlatNode, HashSet<PrefetchPair>> pset1_hash = new Hashtable<FlatNode, HashSet<PrefetchPair>>();
+
+    Set visitset=fm.getNodeSet();
+    while(!visitset.isEmpty()) {
+      FlatNode fn = (FlatNode) visitset.iterator().next();
+      visitset.remove(fn);
+      pset1_hash.put(fn, new HashSet<PrefetchPair>());
+    }
+
+    Set tovisit=fm.getNodeSet();
+    /* Start with a top down sorted order of nodes */
+    while(!tovisit.isEmpty()) {
+      FlatNode fn=(FlatNode)tovisit.iterator().next();
+      tovisit.remove(fn);
+      applyPrefetchInsertRules(fn, tovisit, pset1_hash, newprefetchset);
+    }
+    delSubsetPPairs(newprefetchset);
+  }
+
+  /** This function deletes the smaller prefetch pair subset from a list of prefetch pairs
+   * for e.g. if there are 2 prefetch pairs a.b.c.d and a.b.c for a given flatnode
+   * then this function drops a.b.c from the prefetch set of the flatnode */
+  private void delSubsetPPairs(Hashtable<FlatNode, HashSet<PrefetchPair>> newprefetchset) {
+    for (Enumeration e = newprefetchset.keys(); e.hasMoreElements(); ) {
+      FlatNode fn = (FlatNode) e.nextElement();
+      Set<PrefetchPair> ppairs = newprefetchset.get(fn);
+      Set<PrefetchPair> toremove=new HashSet<PrefetchPair>();
+
+      for(Iterator<PrefetchPair> it1=ppairs.iterator(); it1.hasNext(); ) {
+        PrefetchPair pp1=it1.next();
+        if (toremove.contains(pp1))
+          continue;
+        int l1=pp1.desc.size()+1;
+        for(Iterator<PrefetchPair> it2=ppairs.iterator(); it2.hasNext(); ) {
+          PrefetchPair pp2=it2.next();
+          int l2=pp2.desc.size()+1;
+
+          if (l1<l2&&isSubSet(pp1,pp2))
+            toremove.add(pp1);
+          else
+          if (l2>l1&&isSubSet(pp2,pp1))
+            toremove.add(pp2);
+        }
+      }
+
+      ppairs.removeAll(toremove);
+    }
+  }
+
+  /** This function returns: true if the shorter prefetch pair is a subset of the longer prefetch
+   * pair else it returns: false */
+  private boolean isSubSet(PrefetchPair shrt, PrefetchPair lng) {
+    if (shrt.base != lng.base) {
+      return false;
+    }
+    for (int j = 0; j < shrt.desc.size(); j++) {
+      if(shrt.getDescAt(j) instanceof IndexDescriptor) {
+        IndexDescriptor shrtid = (IndexDescriptor) shrt.getDescAt(j);
+        if(lng.getDescAt(j) instanceof IndexDescriptor) {
+          IndexDescriptor lngid = (IndexDescriptor) lng.getDescAt(j);
+          if(shrtid.equals(lngid)) {
+            continue;
+          } else {
+            return false;
+          }
+        } else {
+          return false;
+        }
+      } else  {
+        if ((Descriptor)shrt.getDescAt(j) != (Descriptor)lng.getDescAt(j)) {
+          return false;
+        }
+      }
+    }
+    return true;
+  }
+
+  /**This function compares all the prefetch pairs in a Prefetch set hashtable and
+   * returns: true if something has changed in the new Prefetch set else
+   * returns: false
+   */
+  private boolean comparePSet1(HashSet<PrefetchPair> oldPSet, HashSet<PrefetchPair>newPSet) {
+    if(oldPSet.size() != newPSet.size()) {
+      return true;
+    } else {
+      for(Iterator it = newPSet.iterator(); it.hasNext(); ) {
+        if(!oldPSet.contains((PrefetchPair)it.next())) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  /** This function creates a set called pset1 that contains prefetch pairs that have already
+   * been prefetched. While traversing the graph of a flat representation in a top down fashion,
+   * this function creates pset1 such that it contains prefetch pairs that have been prefetched at
+   * the previous nodes */
+
+  private void applyPrefetchInsertRules(FlatNode fn, Set tovisit, Hashtable<FlatNode, HashSet<PrefetchPair>> pset1_hash, Hashtable<FlatNode, HashSet<PrefetchPair>> newprefetchset) {
+    if(fn.kind() == FKind.FlatMethod) {
+      HashSet<PrefetchPair> pset1 = new HashSet<PrefetchPair>();
+      Hashtable<PrefetchPair, Double> prefetchset = prefetch_hash.get(fn);
+      for(Enumeration e = prefetchset.keys(); e.hasMoreElements(); ) {
+        PrefetchPair pp = (PrefetchPair) e.nextElement();
+        /* Apply initial rule */
+        if(prefetchset.get(pp).doubleValue() >= PREFETCH_THRESHOLD_PROB) {
+          pset1.add(pp);
+        }
+      }
+      /* Enqueue child node if Pset1 has changed */
+      if (comparePSet1(pset1_hash.get(fn), pset1)) {
+        for(int j=0; j<fn.numNext(); j++) {
+          FlatNode nn = fn.getNext(j);
+          tovisit.add(nn);
+        }
+        pset1_hash.put(fn, pset1);
+      }
+      newprefetchset.put(fn, pset1);
+    } else {     /* Nodes other than Flat Method Node */
+      HashSet<PrefetchPair> pset2 = new HashSet<PrefetchPair>();
+      HashSet<PrefetchPair> newpset = new HashSet<PrefetchPair>();
+      Hashtable<PrefetchPair, Double> prefetchset = prefetch_hash.get(fn);
+      Hashtable<FlatNode, PairMap> ppairmaphash = pmap_hash.get(fn);
+      for(Enumeration epset = prefetchset.keys(); epset.hasMoreElements(); ) {
+        PrefetchPair pp = (PrefetchPair) epset.nextElement();
+        boolean pprobIsGreater = (prefetchset.get(pp).doubleValue() >= PREFETCH_THRESHOLD_PROB);
+        boolean mapprobIsLess=false;
+        boolean mapIsPresent=true;
+        for(int i=0; i<fn.numPrev(); i++) {
+          FlatNode parentnode=fn.getPrev(i);
+          PairMap pm = (PairMap) ppairmaphash.get(parentnode);
+          //Find if probability is less for previous node
+          if(pm!=null&&pm.getPair(pp) != null) {
+            PrefetchPair mappedpp = pm.getPair(pp);
+            if(prefetch_hash.get(parentnode).containsKey(mappedpp)) {
+              double prob = prefetch_hash.get(parentnode).get(mappedpp).doubleValue();
+              if(prob < PREFETCH_THRESHOLD_PROB)
+                mapprobIsLess = true;
+            } else
+              mapprobIsLess = true;
+          } else {
+            mapprobIsLess = true;
+          }
+          /* Build pset2 */
+          if(pm !=null) {
+            HashSet pset = pset1_hash.get(parentnode);
+            if(!pset.contains((PrefetchPair) pm.getPair(pp)))
+              mapIsPresent = false;
+          } else
+            mapIsPresent=false;
+        }
+
+        if(mapIsPresent)
+          pset2.add(pp);
+
+        if(pprobIsGreater && mapprobIsLess)
+          newpset.add(pp);
+      }
+
+      HashSet<PrefetchPair> pset1 = new HashSet<PrefetchPair>();
+      pset1.addAll(pset2);
+      pset1.addAll(newpset);
+
+      /* Enqueue child node if Pset1 has changed */
+      if (comparePSet1(pset1_hash.get(fn), pset1)) {
+        for(int i=0; i<fn.numNext(); i++) {
+          FlatNode nn = fn.getNext(i);
+          tovisit.add(nn);
+        }
+        pset1_hash.put(fn, pset1);
+      }
+
+      /* To insert prefetch, apply rule: if the newpset minus pset2 is nonempty
+       * then insert a new prefetch node here*/
+
+      HashSet<PrefetchPair> s = new HashSet<PrefetchPair>();
+      s.addAll(newpset);
+      s.removeAll(pset2);
+      newprefetchset.put(fn, s);
+    }
+  }
+
+  private void addFlatPrefetchNode(Hashtable<FlatNode, HashSet<PrefetchPair>> newprefetchset) {
+    /* This modifies the Flat representation graph */
+    for(Enumeration e = newprefetchset.keys(); e.hasMoreElements(); ) {
+      FlatNode fn = (FlatNode) e.nextElement();
+      FlatPrefetchNode fpn = new FlatPrefetchNode();
+      if(newprefetchset.get(fn).size() > 0) {
+        fpn.insAllpp((HashSet)newprefetchset.get(fn));
+        if(fn.kind() == FKind.FlatMethod) {
+          FlatNode nn = fn.getNext(0);
+          fn.setNext(0, fpn);
+          fpn.addNext(nn);
+          fpn.siteid = prefetchsiteid++;
+        } else {
+          /* Check if previous node of this FlatNode is a NEW node
+           * If yes, delete this flatnode and its prefetch set from hash table
+           * This eliminates prefetches for NULL ptrs*/
+          while(fn.numPrev() > 0) {
+            FlatNode nn = fn.getPrev(0);
+            for(int j = 0; j<nn.numNext(); j++) {
+              if(nn.getNext(j) == fn) {
+                nn.setNext(j, fpn);
+              }
+            }
+          }
+          fpn.addNext(fn);
+          fpn.siteid = prefetchsiteid++;
+        }   //end of else
+      }       //End of if
+    }     //end of for
+  }
 }