private boolean debugMode;
private boolean stateReductionMode;
private final PrintWriter out;
- volatile private String detail;
- volatile private int depth;
- volatile private int id;
- Transition transition;
+ private String detail;
+ private int depth;
+ private int id;
+ private Transition transition;
// State reduction fields
private Integer[] choices;
+ private Integer[] refChoices;
private IntChoiceFromSet currCG;
private int choiceCounter;
private Integer choiceUpperBound;
// Stores explored backtrack lists in the form of HashSet of Strings
private HashSet<String> backtrackSet;
private HashMap<Integer, HashSet<Integer>> conflictPairMap;
- // Map choicelist with start index
- // private HashMap<Integer[],Integer> choiceListStartIndexMap;
// Map that represents graph G
// (i.e., visible operation dependency graph (VOD Graph)
// Set that represents hash table H
// (i.e., hash table that records encountered states)
// VOD graph is updated when the state has not yet been seen
- private HashSet<Integer> visitedStateSet;
// Current state
- private int stateId;
+ private HashSet<Integer> justVisitedStates;
// Previous choice number
private int prevChoiceValue;
+ // HashSet that stores references to unused CGs
+ private HashSet<IntChoiceFromSet> unusedCG;
+
+ //private HashMap<Integer, ConflictTracker.Node> stateGraph;
+ private HashMap<Integer, HashSet<Integer>> stateToEventMap;
+ // Map state to event
+ // Visited states in the previous and current executions/traces for terminating condition
+ private HashSet<Integer> prevVisitedStates;
+ private HashSet<Integer> currVisitedStates;
public StateReducer(Config config, JPF jpf) {
debugMode = config.getBoolean("debug_state_transition", false);
transition = null;
isBooleanCGFlipped = false;
vodGraphMap = new HashMap<>();
- visitedStateSet = new HashSet<>();
- stateId = -1;
+ justVisitedStates = new HashSet<>();
prevChoiceValue = -1;
+ cgMap = new HashMap<>();
+ readWriteFieldsMap = new HashMap<>();
+ backtrackMap = new HashMap<>();
+ backtrackSet = new HashSet<>();
+ conflictPairMap = new HashMap<>();
+ unusedCG = new HashSet<>();
+ stateToEventMap = new HashMap<>();
+ prevVisitedStates = new HashSet<>();
+ currVisitedStates = new HashSet<>();
initializeStateReduction();
}
private void initializeStateReduction() {
if (stateReductionMode) {
choices = null;
+ refChoices = null;
currCG = null;
choiceCounter = 0;
choiceUpperBound = 0;
maxUpperBound = 0;
isInitialized = false;
isResetAfterAnalysis = false;
- cgMap = new HashMap<>();
- readWriteFieldsMap = new HashMap<>();
- backtrackMap = new HashMap<>();
- backtrackSet = new HashSet<>();
- conflictPairMap = new HashMap<>();
+ cgMap.clear();
+ resetReadWriteAnalysis();
+ backtrackMap.clear();
+ backtrackSet.clear();
}
}
}
}
+ private void resetReadWriteAnalysis() {
+ // Reset the following data structure when the choice counter reaches 0 again
+ conflictPairMap.clear();
+ readWriteFieldsMap.clear();
+ }
+
+ private IntChoiceFromSet setNewCG(IntChoiceFromSet icsCG) {
+ icsCG.setNewValues(choices);
+ icsCG.reset();
+ // Use a modulo since choiceCounter is going to keep increasing
+ int choiceIndex = choiceCounter % choices.length;
+ icsCG.advance(choices[choiceIndex]);
+ if (choiceIndex == 0) {
+ resetReadWriteAnalysis();
+ }
+ return icsCG;
+ }
+
+ private Integer[] copyChoices(Integer[] choicesToCopy) {
+
+ Integer[] copyOfChoices = new Integer[choicesToCopy.length];
+ System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
+ return copyOfChoices;
+ }
+
+ private void continueExecutingThisTrace(IntChoiceFromSet icsCG) {
+ // We repeat the same trace if a state match is not found yet
+ IntChoiceFromSet setCG = setNewCG(icsCG);
+ unusedCG.add(setCG);
+ }
+
+ private void initializeChoiceGenerators(IntChoiceFromSet icsCG, Integer[] cgChoices) {
+ if (choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
+ // Update the choices of the first CG and add '-1'
+ if (choices == null) {
+ // Initialize backtrack set that stores all the explored backtrack lists
+ maxUpperBound = cgChoices.length;
+ // All the choices are always the same so we only need to update it once
+ // Get the choice array and final choice in the array
+ choices = cgChoices;
+ // Make a copy of choices as reference
+ refChoices = copyChoices(choices);
+ String firstChoiceListString = buildStringFromChoiceList(choices);
+ backtrackSet.add(firstChoiceListString);
+ }
+ IntChoiceFromSet setCG = setNewCG(icsCG);
+ cgMap.put(setCG, refChoices[choiceCounter]);
+ } else {
+ continueExecutingThisTrace(icsCG);
+ }
+ }
+
+ private void manageChoiceGeneratorsInSubsequentTraces(IntChoiceFromSet icsCG) {
+ // If this is the first iteration of the trace then set other CGs done
+ if (choiceCounter <= choiceUpperBound) {
+ icsCG.setDone();
+ } else {
+ // If this is the subsequent iterations of the trace then set up new CGs to continue the execution
+ continueExecutingThisTrace(icsCG);
+ }
+ }
+
@Override
public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
if (stateReductionMode) {
isInitialized = true;
}
// Record the subsequent Integer CGs only until we hit the upper bound
- if (!isResetAfterAnalysis && choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
- // Update the choices of the first CG and add '-1'
- if (choices == null) {
- // Initialize backtrack set that stores all the explored backtrack lists
- maxUpperBound = cgChoices.length;
- // All the choices are always the same so we only need to update it once
- choices = new Integer[cgChoices.length + 1];
- System.arraycopy(cgChoices, 0, choices, 0, cgChoices.length);
- choices[choices.length - 1] = -1;
- String firstChoiceListString = buildStringFromChoiceList(choices);
- backtrackSet.add(firstChoiceListString);
- }
- icsCG.setNewValues(choices);
- icsCG.reset();
- // Advance the current Integer CG
- // This way we explore all the event numbers in the first pass
- icsCG.advance(choices[choiceCounter]);
- cgMap.put(icsCG, choices[choiceCounter]);
- choiceCounter++;
+ if (!isResetAfterAnalysis) {
+ initializeChoiceGenerators(icsCG, cgChoices);
} else {
- // Set done the subsequent CGs
- // We only need n CGs (n is event numbers)
- icsCG.setDone();
+ // Set new CGs to done so that the search algorithm explores the existing CGs
+ //icsCG.setDone();
+ manageChoiceGeneratorsInSubsequentTraces(icsCG);
}
+ choiceCounter++;
}
}
}
+ private void setDoneUnusedCG() {
+ // Set done every CG in the unused CG set
+ for (IntChoiceFromSet cg : unusedCG) {
+ cg.setDone();
+ }
+ unusedCG.clear();
+ }
+
private void resetAllCGs() {
// Extract the event numbers that have backtrack lists
Set<Integer> eventSet = backtrackMap.keySet();
// Return if there is no conflict at all (highly unlikely)
if (eventSet.isEmpty()) {
+ // Set every CG to done!
+ for (IntChoiceFromSet cg : cgMap.keySet()) {
+ cg.setDone();
+ }
return;
}
// Reset every CG with the first backtrack lists
cg.setDone();
}
}
+ setDoneUnusedCG();
+ saveVisitedStates();
+ }
+
+ // 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) {
+
+ HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
+ boolean containsCyclesWithAllEvts = false;
+ if (checkIfAllEventsInvolved(visitedEvents)) {
+ containsCyclesWithAllEvts = true;
+ }
+
+ return containsCyclesWithAllEvts;
+ }
+
+ private boolean checkIfAllEventsInvolved(HashSet<Integer> visitedEvents) {
+
+ // Check if this set contains all the event choices
+ // If not then this is not the terminating condition
+ for(int i=0; i<=choiceUpperBound; i++) {
+ if (!visitedEvents.contains(i)) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ private void saveVisitedStates() {
+ // CG is being reset
+ // Save all the visited states
+ prevVisitedStates.addAll(currVisitedStates);
+ currVisitedStates.clear();
+ }
+
+ private void updateChoicesForNewExecution(IntChoiceFromSet icsCG) {
+ if (choices == null || choices != icsCG.getAllChoices()) {
+ currCG = icsCG;
+ choices = icsCG.getAllChoices();
+ refChoices = copyChoices(choices);
+ // Reset a few things for the sub-graph
+ resetReadWriteAnalysis();
+ choiceCounter = 0;
+ }
+ }
+
+ private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
+ // Traverse the sub-graphs
+ if (isResetAfterAnalysis) {
+ // Do this for every CG after finishing each backtrack list
+ // We try to update the CG with a backtrack list if the state has been visited multiple times
+ //if ((icsCG.getNextChoice() == -1 || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
+ //if ((!icsCG.hasMoreChoices() || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
+ if (choiceCounter > 1 && cgMap.containsKey(icsCG)) {
+ int event = cgMap.get(icsCG);
+ LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
+ if (choiceLists != null && choiceLists.peekFirst() != null) {
+ Integer[] choiceList = choiceLists.removeFirst();
+ // Deploy the new choice list for this CG
+ icsCG.setNewValues(choiceList);
+ icsCG.reset();
+ } else {
+ // Set done if this was the last backtrack list
+ icsCG.setDone();
+ }
+ setDoneUnusedCG();
+ saveVisitedStates();
+ }
+ } else {
+ // Update and reset the CG if needed (do this for the first time after the analysis)
+ // Start backtracking if this is a visited state and it is not a repeating state
+ resetAllCGs();
+ isResetAfterAnalysis = true;
+ }
+ }
+
+ 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 - 1) % refChoices.length;
+ if (choices[choiceIndex] != icsCG.getNextChoiceIndex()) {
+ int expectedChoice = refChoices[choiceIndex];
+ int currCGIndex = icsCG.getNextChoiceIndex();
+ if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
+ icsCG.setChoice(currCGIndex, expectedChoice);
+ }
+ }
+ }
+
+ 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;
}
@Override
if (currentCG instanceof IntChoiceFromSet) {
IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
// Update the current pointer to the current set of choices
- if (choices == null || choices != icsCG.getAllChoices()) {
- currCG = icsCG;
- choices = icsCG.getAllChoices();
- // Reset a few things for the sub-graph
- conflictPairMap.clear();
- readWriteFieldsMap.clear();
- choiceCounter = 0;
- }
- // Traverse the sub-graphs
- if (isResetAfterAnalysis) {
- // Advance choice counter for sub-graphs
- choiceCounter++;
- // Do this for every CG after finishing each backtrack list
- if (icsCG.getNextChoice() == -1 || visitedStateSet.contains(stateId)) {
- int event = cgMap.get(icsCG);
- LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
- if (choiceLists != null && choiceLists.peekFirst() != null) {
- Integer[] choiceList = choiceLists.removeFirst();
- // Deploy the new choice list for this CG
- icsCG.setNewValues(choiceList);
- icsCG.reset();
- } else {
- // Set done if this was the last backtrack list
- icsCG.setDone();
- }
- }
- }
- // Update and reset the CG if needed (do this for the first time after the analysis)
- if (!isResetAfterAnalysis && icsCG.getNextChoice() == -1) {
- resetAllCGs();
- isResetAfterAnalysis = true;
+ updateChoicesForNewExecution(icsCG);
+ // Check if we have seen this state or this state contains cycles that involve all events
+ if (terminateCurrentExecution()) {
+ exploreNextBacktrackSets(icsCG);
}
+ justVisitedStates.clear();
+ // If we don't see a fair scheduling of events/choices then we have to enforce it
+ checkAndEnforceFairScheduling(icsCG);
+ // Update the VOD graph always with the latest
+ updateVODGraph(icsCG.getNextChoice());
}
}
}
- public void updateVODGraph(int prevChoice, int currChoice) {
-
+ private void updateVODGraph(int currChoiceValue) {
+ // Update the graph when we have the current choice value
HashSet<Integer> choiceSet;
- if (vodGraphMap.containsKey(prevChoice)) {
+ if (vodGraphMap.containsKey(prevChoiceValue)) {
// If the key already exists, just retrieve it
- choiceSet = vodGraphMap.get(prevChoice);
+ choiceSet = vodGraphMap.get(prevChoiceValue);
} else {
// Create a new entry
choiceSet = new HashSet<>();
- vodGraphMap.put(prevChoice, choiceSet);
+ vodGraphMap.put(prevChoiceValue, choiceSet);
+ }
+ choiceSet.add(currChoiceValue);
+ prevChoiceValue = currChoiceValue;
+ }
+
+ private void mapStateToEvent(Search search, int stateId) {
+ // Insert state ID and event choice into the map
+ HashSet<Integer> eventSet;
+ if (stateToEventMap.containsKey(stateId)) {
+ eventSet = stateToEventMap.get(stateId);
+ } else {
+ eventSet = new HashSet<>();
+ stateToEventMap.put(stateId, eventSet);
+ }
+ eventSet.add(prevChoiceValue);
+ }
+
+ private void updateStateInfo(Search search) {
+ if (stateReductionMode) {
+ // Update the state variables
+ // Line 19 in the paper page 11 (see the heading note above)
+ int stateId = search.getStateId();
+ currVisitedStates.add(stateId);
+ mapStateToEvent(search, stateId);
+ justVisitedStates.add(stateId);
}
- choiceSet.add(currChoice);
}
@Override
out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
" which is " + detail + " Transition: " + transition + "\n");
}
- if (stateReductionMode) {
- // Update vodGraph
- int currChoice = choiceCounter - 1;
- if (currChoice < 0 || currChoice > choices.length - 1 || choices[currChoice] == -1 || prevChoiceValue == choices[currChoice]) {
- // Handle all corner cases (e.g., out of bound values)
- return;
- }
- // When current choice is 0, previous choice could be -1
- updateVODGraph(prevChoiceValue, choices[currChoice]);
- // Current choice becomes previous choice in the next iteration
- prevChoiceValue = choices[currChoice];
- // Line 19 in the paper page 11 (see the heading note above)
- stateId = search.getStateId();
- // Add state ID into the visited state set
- visitedStateSet.add(stateId);
- }
+ updateStateInfo(search);
}
@Override
out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
" and depth: " + depth + "\n");
}
+ updateStateInfo(search);
}
@Override
// Do the analysis to get Read and Write accesses to fields
ReadWriteSet rwSet;
// We already have an entry
- if (readWriteFieldsMap.containsKey(choices[currentChoice])) {
- rwSet = readWriteFieldsMap.get(choices[currentChoice]);
+ if (readWriteFieldsMap.containsKey(refChoices[currentChoice])) {
+ rwSet = readWriteFieldsMap.get(refChoices[currentChoice]);
} else { // We need to create a new entry
rwSet = new ReadWriteSet();
- readWriteFieldsMap.put(choices[currentChoice], rwSet);
+ readWriteFieldsMap.put(refChoices[currentChoice], rwSet);
}
int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
// Record the field in the map
}
int maxListLength = choiceUpperBound + 1;
int listLength = maxListLength - conflictEventNumber;
- Integer[] newChoiceList = new Integer[listLength + 1];
+ Integer[] newChoiceList = new Integer[listLength];
// Put the conflicting event numbers first and reverse the order
- newChoiceList[0] = choices[currentChoice];
- newChoiceList[1] = choices[conflictEventNumber];
+ newChoiceList[0] = refChoices[currentChoice];
+ newChoiceList[1] = refChoices[conflictEventNumber];
// Put the rest of the event numbers into the array starting from the minimum to the upper bound
for (int i = conflictEventNumber + 1, j = 2; j < listLength; i++) {
- if (choices[i] != choices[currentChoice]) {
- newChoiceList[j] = choices[i];
+ if (refChoices[i] != refChoices[currentChoice]) {
+ newChoiceList[j] = refChoices[i];
j++;
}
}
- // Set the last element to '-1' as the end of the sequence
- newChoiceList[newChoiceList.length - 1] = -1;
checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
// The start index for the recursion is always 1 (from the main branch)
} else { // This is a sub-graph
// There is a case/bug that after a re-initialization, currCG is not yet initialized
- if (currCG != null) {
+ if (currCG != null && cgMap.containsKey(currCG)) {
int backtrackListIndex = cgMap.get(currCG);
backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
- int listLength = choices.length;
+ int listLength = refChoices.length;
Integer[] newChoiceList = new Integer[listLength];
// Copy everything before the conflict number
for (int i = 0; i < conflictEventNumber; i++) {
- newChoiceList[i] = choices[i];
+ newChoiceList[i] = refChoices[i];
}
// Put the conflicting events
- newChoiceList[conflictEventNumber] = choices[currentChoice];
- newChoiceList[conflictEventNumber + 1] = choices[conflictEventNumber];
+ newChoiceList[conflictEventNumber] = refChoices[currentChoice];
+ newChoiceList[conflictEventNumber + 1] = refChoices[conflictEventNumber];
// Copy the rest
for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
- if (choices[i] != choices[currentChoice]) {
- newChoiceList[j] = choices[i];
+ if (refChoices[i] != refChoices[currentChoice]) {
+ newChoiceList[j] = refChoices[i];
j++;
}
}
- // Set the last element to '-1' as the end of the sequence
- newChoiceList[newChoiceList.length - 1] = -1;
checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
}
}
if (currChoiceNextNodes != null) {
// Add only if there is a mapping for next nodes
for (Integer nextNode : currChoiceNextNodes) {
+ // Skip cycles
+ if (nextNode == currChoice) {
+ continue;
+ }
nodesToVisit.addLast(nextNode);
}
}
public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
if (stateReductionMode) {
if (isInitialized) {
- if (choiceCounter > choices.length - 1) {
+ int currentChoice = (choiceCounter % refChoices.length) - 1;
+ if (currentChoice < 0) {
// We do not compute the conflicts for the choice '-1'
return;
}
- int currentChoice = choiceCounter - 1;
// Record accesses from executed instructions
if (executedInsn instanceof JVMFieldInstruction) {
// Analyze only after being initialized
// one by one as this recursively checks backward when backtrack set is revisited and executed.
for (int eventNumber = currentChoice - 1; eventNumber >= 0; eventNumber--) {
// Skip if this event number does not have any Read/Write set
- if (!readWriteFieldsMap.containsKey(choices[eventNumber])) {
+ if (!readWriteFieldsMap.containsKey(refChoices[eventNumber])) {
continue;
}
- ReadWriteSet rwSet = readWriteFieldsMap.get(choices[eventNumber]);
+ ReadWriteSet rwSet = readWriteFieldsMap.get(refChoices[eventNumber]);
int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
// 1) Check for conflicts with Write fields for both Read and Write instructions
if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
// If it has been serviced before, we just skip this
if (recordConflictPair(currentChoice, eventNumber)) {
// Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
- if (!visitedStateSet.contains(stateId)||
- (visitedStateSet.contains(stateId) && isReachableInVODGraph(choices[currentChoice], choices[currentChoice-1]))) {
+ if (vm.isNewState() || isReachableInVODGraph(refChoices[currentChoice], refChoices[currentChoice-1])) {
createBacktrackChoiceList(currentChoice, eventNumber);
// Break if a conflict is found!
break;
projects / jpf-core.git / blobdiff