From: rtrimana <rtrimana@uci.edu>
Date: Wed, 1 Apr 2020 23:44:57 +0000 (-0700)
Subject: Reimplementing DPOR Phase 1: First trace execution, cycle detection, R/W field access... 
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;ds=sidebyside;h=cbebe94f5164064cb48640d6025de04fc47d637f;p=jpf-core.git

Reimplementing DPOR Phase 1: First trace execution, cycle detection, R/W field access analysis.
---

diff --git a/main.jpf b/main.jpf
index 0948c38..0665ff2 100644
--- a/main.jpf
+++ b/main.jpf
@@ -46,7 +46,7 @@ apps=App1,App2
 #debug_mode=true
 
 # Debug mode for StateReducer
-#printout_state_transition=true
+printout_state_transition=true
 #activate_state_reduction=true
 
 # Timeout in minutes (default is 0 which means no timeout)
diff --git a/src/main/gov/nasa/jpf/listener/DPORStateReducer.java b/src/main/gov/nasa/jpf/listener/DPORStateReducer.java
index 746adfe..a688754 100644
--- a/src/main/gov/nasa/jpf/listener/DPORStateReducer.java
+++ b/src/main/gov/nasa/jpf/listener/DPORStateReducer.java
@@ -48,7 +48,7 @@ import java.util.*;
  */
 public class DPORStateReducer extends ListenerAdapter {
 
-  // Debug info fields
+  // Information printout fields for verbose mode
   private boolean verboseMode;
   private boolean stateReductionMode;
   private final PrintWriter out;
@@ -57,6 +57,25 @@ public class DPORStateReducer extends ListenerAdapter {
   private int id;
   private Transition transition;
 
+  // DPOR-related fields
+  private Integer[] choices;
+  private Integer[] refChoices;
+  private int choiceCounter;
+  private int maxEventChoice;
+  // Record CGs for backtracking points
+  private List<IntChoiceFromSet> cgList;
+  // Data structure to track the events seen by each state to track cycles (containing all events) for termination
+  private HashMap<Integer, HashSet<Integer>> stateToEventMap;
+  private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
+  private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
+  private HashSet<Integer> currVisitedStates; // States being visited in the current execution
+  // Data structure to analyze field Read/Write accesses
+  private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
+  private HashMap<Integer, HashSet<Integer>> conflictPairMap;
+
+  // Boolean states
+  private boolean isBooleanCGFlipped;
+
   public DPORStateReducer(Config config, JPF jpf) {
     verboseMode = config.getBoolean("printout_state_transition", false);
     stateReductionMode = config.getBoolean("activate_state_reduction", true);
@@ -65,6 +84,20 @@ public class DPORStateReducer extends ListenerAdapter {
     } else {
       out = null;
     }
+    // DPOR-related
+    choices = null;
+    refChoices = null;
+    choiceCounter = 0;
+    maxEventChoice = 0;
+    cgList = new ArrayList<>();
+    stateToEventMap = new HashMap<>();
+    justVisitedStates = new HashSet<>();
+    prevVisitedStates = new HashSet<>();
+    currVisitedStates = new HashSet<>();
+    readWriteFieldsMap = new HashMap<>();
+    conflictPairMap = new HashMap<>();
+    // Booleans
+    isBooleanCGFlipped = false;
   }
 
   @Override
@@ -105,6 +138,9 @@ public class DPORStateReducer extends ListenerAdapter {
       out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
               " which is " + detail + " Transition: " + transition + "\n");
     }
+    if (stateReductionMode) {
+      updateStateInfo(search);
+    }
   }
 
   @Override
@@ -118,6 +154,9 @@ public class DPORStateReducer extends ListenerAdapter {
       out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
               " and depth: " + depth + "\n");
     }
+    if (stateReductionMode) {
+      updateStateInfo(search);
+    }
   }
 
   @Override
@@ -126,4 +165,402 @@ public class DPORStateReducer extends ListenerAdapter {
       out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
     }
   }
+
+  @Override
+  public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
+    if (stateReductionMode) {
+      // Initialize with necessary information from the CG
+      if (nextCG instanceof IntChoiceFromSet) {
+        IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
+        // Check if CG has been initialized, otherwise initialize it
+        Integer[] cgChoices = icsCG.getAllChoices();
+        // Record the events (from choices)
+        if (choices == null) {
+          choices = cgChoices;
+          // Make a copy of choices as reference
+          refChoices = copyChoices(choices);
+          // Record the max event choice (the last element of the choice array)
+          maxEventChoice = choices[choices.length - 1];
+        }
+        // Use a modulo since choiceCounter is going to keep increasing
+        int choiceIndex = choiceCounter % choices.length;
+        icsCG.advance(choices[choiceIndex]);
+        // Index the ChoiceGenerator to set backtracking points
+        cgList.add(icsCG);
+      }
+    }
+  }
+
+  @Override
+  public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
+
+    if (stateReductionMode) {
+      // Check the boolean CG and if it is flipped, we are resetting the analysis
+//      if (currentCG instanceof BooleanChoiceGenerator) {
+//        if (!isBooleanCGFlipped) {
+//          isBooleanCGFlipped = true;
+//        } else {
+//          initializeStateReduction();
+//        }
+//      }
+      // Check every choice generated and ensure fair scheduling!
+      if (currentCG instanceof IntChoiceFromSet) {
+        IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
+        // If we don't see a fair scheduling of events/choices then we have to enforce it
+        checkAndEnforceFairScheduling(icsCG);
+        // Map state to event
+        mapStateToEvent(icsCG.getNextChoice());
+        // Check if we have seen this state or this state contains cycles that involve all events
+        if (terminateCurrentExecution()) {
+          exploreNextBacktrackSets(icsCG);
+        }
+        justVisitedStates.clear();
+        choiceCounter++;
+      }
+    }
+  }
+
+  @Override
+  public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
+    if (stateReductionMode) {
+      // Has to be initialized and a integer CG
+      ChoiceGenerator<?> cg = vm.getChoiceGenerator();
+      if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
+        int currentChoice = choiceCounter - 1;  // Accumulative choice w.r.t the current trace
+        //if (getCurrentChoice(vm) < 0) { // If choice is -1 then skip
+        if (currentChoice < 0) { // If choice is -1 then skip
+          return;
+        }
+        // Record accesses from executed instructions
+        if (executedInsn instanceof JVMFieldInstruction) {
+          // Analyze only after being initialized
+          String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
+          // We don't care about libraries
+          if (!isFieldExcluded(fieldClass)) {
+            analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
+          }
+        } else if (executedInsn instanceof INVOKEINTERFACE) {
+          // Handle the read/write accesses that occur through iterators
+          analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
+        }
+        // Analyze conflicts from next instructions
+        if (nextInsn instanceof JVMFieldInstruction) {
+          // Skip the constructor because it is called once and does not have shared access with other objects
+          if (!nextInsn.getMethodInfo().getName().equals("<init>")) {
+            String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
+            if (!isFieldExcluded(fieldClass)) {
+              // Check for conflict (go backward from current choice and get the first conflict)
+              for (int evtCntr = currentChoice - 1; evtCntr >= 0; evtCntr--) {
+                if (!readWriteFieldsMap.containsKey(evtCntr)) { // Skip if this event does not have any Read/Write set
+                  continue;
+                }
+                ReadWriteSet rwSet = readWriteFieldsMap.get(evtCntr);
+                int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
+                // Check for conflicts with Write fields for both Read and Write instructions
+                if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
+                      rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
+                     (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
+                      rwSet.readFieldObjectId(fieldClass) == currObjId)) {
+                  // Check and record a backtrack set for just once!
+                  if (successfullyRecordConflictPair(currentChoice, evtCntr)) {
+                    // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
+//                    if (vm.isNewState() || isReachableInVODGraph(refChoices[currentChoice], refChoices[currentChoice-1])) {
+//                      createBacktrackChoiceList(currentChoice, eventNumber);
+//                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+
+  // == HELPERS
+  // -- INNER CLASS
+  // This class compactly stores Read and Write field sets
+  // We store the field name and its object ID
+  // Sharing the same field means the same field name and object ID
+  private class ReadWriteSet {
+    private HashMap<String, Integer> readSet;
+    private HashMap<String, Integer> writeSet;
+
+    public ReadWriteSet() {
+      readSet = new HashMap<>();
+      writeSet = new HashMap<>();
+    }
+
+    public void addReadField(String field, int objectId) {
+      readSet.put(field, objectId);
+    }
+
+    public void addWriteField(String field, int objectId) {
+      writeSet.put(field, objectId);
+    }
+
+    public boolean readFieldExists(String field) {
+      return readSet.containsKey(field);
+    }
+
+    public boolean writeFieldExists(String field) {
+      return writeSet.containsKey(field);
+    }
+
+    public int readFieldObjectId(String field) {
+      return readSet.get(field);
+    }
+
+    public int writeFieldObjectId(String field) {
+      return writeSet.get(field);
+    }
+  }
+
+  // -- CONSTANTS
+  private final static String DO_CALL_METHOD = "doCall";
+  // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
+  private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
+  private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
+          // Groovy library created fields
+          {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
+          // Infrastructure
+          "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
+          "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
+  private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
+          // Java and Groovy libraries
+          { "java", "org", "sun", "com", "gov", "groovy"};
+  private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
+  private final static String GET_PROPERTY_METHOD =
+          "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
+  private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
+  private final static String JAVA_INTEGER = "int";
+  private final static String JAVA_STRING_LIB = "java.lang.String";
+
+  // -- FUNCTIONS
+  private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
+    // Check the next choice and if the value is not the same as the expected then force the expected value
+    int choiceIndex = choiceCounter % refChoices.length;
+    int nextChoice = icsCG.getNextChoice();
+    if (refChoices[choiceIndex] != nextChoice) {
+      int expectedChoice = refChoices[choiceIndex];
+      int currCGIndex = icsCG.getNextChoiceIndex();
+      if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
+        icsCG.setChoice(currCGIndex, expectedChoice);
+      }
+    }
+  }
+
+  private Integer[] copyChoices(Integer[] choicesToCopy) {
+
+    Integer[] copyOfChoices = new Integer[choicesToCopy.length];
+    System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
+    return copyOfChoices;
+  }
+
+  // --- Functions related to cycle detection
+
+  // Detect cycles in the current execution/trace
+  // We terminate the execution iff:
+  // (1) the state has been visited in the current execution
+  // (2) the state has one or more cycles that involve all the events
+  // With simple approach we only need to check for a re-visited state.
+  // Basically, we have to check that we have executed all events between two occurrences of such state.
+  private boolean containsCyclesWithAllEvents(int stId) {
+
+    // False if the state ID hasn't been recorded
+    if (!stateToEventMap.containsKey(stId)) {
+      return false;
+    }
+    HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
+    // Check if this set contains all the event choices
+    // If not then this is not the terminating condition
+    for(int i=0; i<=maxEventChoice; i++) {
+      if (!visitedEvents.contains(i)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  private void mapStateToEvent(int nextChoiceValue) {
+    // Update all states with this event/choice
+    // This means that all past states now see this transition
+    Set<Integer> stateSet = stateToEventMap.keySet();
+    for(Integer stateId : stateSet) {
+      HashSet<Integer> eventSet = stateToEventMap.get(stateId);
+      eventSet.add(nextChoiceValue);
+    }
+  }
+
+  private boolean terminateCurrentExecution() {
+    // We need to check all the states that have just been visited
+    // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
+    for(Integer stateId : justVisitedStates) {
+      if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private void updateStateInfo(Search search) {
+    // Update the state variables
+    // Line 19 in the paper page 11 (see the heading note above)
+    int stateId = search.getStateId();
+    currVisitedStates.add(stateId);
+    // Insert state ID into the map if it is new
+    if (!stateToEventMap.containsKey(stateId)) {
+      HashSet<Integer> eventSet = new HashSet<>();
+      stateToEventMap.put(stateId, eventSet);
+    }
+    justVisitedStates.add(stateId);
+  }
+
+  // --- Functions related to Read/Write access analysis on shared fields
+
+  // Analyze Read/Write accesses that are directly invoked on fields
+  private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
+    // Do the analysis to get Read and Write accesses to fields
+    ReadWriteSet rwSet = getReadWriteSet(currentChoice);
+    int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
+    // Record the field in the map
+    if (executedInsn instanceof WriteInstruction) {
+      // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
+      for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
+        if (fieldClass.startsWith(str)) {
+          return;
+        }
+      }
+      rwSet.addWriteField(fieldClass, objectId);
+    } else if (executedInsn instanceof ReadInstruction) {
+      rwSet.addReadField(fieldClass, objectId);
+    }
+  }
+
+  // Analyze Read accesses that are indirect (performed through iterators)
+  // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
+  private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
+    // Get method name
+    INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
+    if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
+            insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
+      // Extract info from the stack frame
+      StackFrame frame = ti.getTopFrame();
+      int[] frameSlots = frame.getSlots();
+      // Get the Groovy callsite library at index 0
+      ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
+      if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
+        return;
+      }
+      // Get the iterated object whose property is accessed
+      ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
+      // We exclude library classes (they start with java, org, etc.) and some more
+      String objClassName = eiAccessObj.getClassInfo().getName();
+      if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
+          excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName)) {
+        return;
+      }
+      // Extract fields from this object and put them into the read write
+      int numOfFields = eiAccessObj.getNumberOfFields();
+      for(int i=0; i<numOfFields; i++) {
+        FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
+        if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
+          String fieldClass = fieldInfo.getFullName();
+          ReadWriteSet rwSet = getReadWriteSet(currentChoice);
+          int objectId = fieldInfo.getClassInfo().getClassObjectRef();
+          // Record the field in the map
+          rwSet.addReadField(fieldClass, objectId);
+        }
+      }
+    }
+  }
+
+  private boolean excludeThisForItContains(String[] excludedStrings, String className) {
+    for (String excludedField : excludedStrings) {
+      if (className.contains(excludedField)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
+    for (String excludedField : excludedStrings) {
+      if (className.endsWith(excludedField)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
+    for (String excludedField : excludedStrings) {
+      if (className.startsWith(excludedField)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
+    // Save all the visited states when starting a new execution of trace
+    prevVisitedStates.addAll(currVisitedStates);
+    currVisitedStates.clear();
+
+  }
+
+  private int getCurrentChoice(VM vm) {
+    ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
+    // This is the main event CG
+    if (currentCG instanceof IntChoiceFromSet) {
+      return ((IntChoiceFromSet) currentCG).getNextChoiceIndex();
+    } else {
+      // This is the interval CG used in device handlers
+      ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
+      return ((IntChoiceFromSet) parentCG).getNextChoiceIndex();
+    }
+  }
+
+  private ReadWriteSet getReadWriteSet(int currentChoice) {
+    // Do the analysis to get Read and Write accesses to fields
+    ReadWriteSet rwSet;
+    // We already have an entry
+    if (readWriteFieldsMap.containsKey(currentChoice)) {
+      rwSet = readWriteFieldsMap.get(currentChoice);
+    } else { // We need to create a new entry
+      rwSet = new ReadWriteSet();
+      readWriteFieldsMap.put(currentChoice, rwSet);
+    }
+    return rwSet;
+  }
+
+  private boolean isFieldExcluded(String field) {
+    // Check against "starts-with", "ends-with", and "contains" list
+    if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
+            excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
+            excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
+      return true;
+    }
+
+    return false;
+  }
+
+  private boolean successfullyRecordConflictPair(int currentEvent, int eventNumber) {
+    HashSet<Integer> conflictSet;
+    if (!conflictPairMap.containsKey(currentEvent)) {
+      conflictSet = new HashSet<>();
+      conflictPairMap.put(currentEvent, conflictSet);
+    } else {
+      conflictSet = conflictPairMap.get(currentEvent);
+    }
+    // If this conflict has been recorded before, we return false because
+    // we don't want to service this backtrack point twice
+    if (conflictSet.contains(eventNumber)) {
+      return false;
+    }
+    // If it hasn't been recorded, then do otherwise
+    conflictSet.add(eventNumber);
+    return true;
+  }
 }
diff --git a/src/main/gov/nasa/jpf/listener/StateReducer.java b/src/main/gov/nasa/jpf/listener/StateReducer.java
index a1a01c2..b17b29a 100644
--- a/src/main/gov/nasa/jpf/listener/StateReducer.java
+++ b/src/main/gov/nasa/jpf/listener/StateReducer.java
@@ -421,9 +421,6 @@ public class StateReducer extends ListenerAdapter {
   public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
 
     if (stateReductionMode) {
-      if (vm.getNextChoiceGenerator() instanceof BooleanChoiceGenerator) {
-        System.out.println("Next CG is a booleanCG");
-      }
       // Check the boolean CG and if it is flipped, we are resetting the analysis
       if (currentCG instanceof BooleanChoiceGenerator) {
         if (!isBooleanCGFlipped) {