* This DPOR implementation is augmented by the algorithm presented in this SPIN paper:
* http://spinroot.com/spin/symposia/ws08/spin2008_submission_33.pdf
*
- * The algorithm is presented on page 11 of the paper. Basically, we create a graph G
- * (i.e., visible operation dependency graph)
- * that maps inter-related threads/sub-programs that trigger state changes.
- * The key to this approach is that we evaluate graph G in every iteration/recursion to
- * only update the backtrack sets of the threads/sub-programs that are reachable in graph G
- * from the currently running thread/sub-program.
+ * The algorithm is presented on page 11 of the paper. Basically, we have a graph G
+ * (i.e., visible operation dependency graph).
+ * This DPOR implementation actually fixes the algorithm in the SPIN paper that does not
+ * consider cases where a state could be matched early. In this new algorithm/implementation,
+ * each run is terminated iff:
+ * - we find a state that matches a state in a previous run, or
+ * - we have a matched state in the current run that consists of cycles that contain all choices/events.
*/
public class DPORStateReducer extends ListenerAdapter {
// DPOR-related fields
// Basic information
private Integer[] choices;
- private Integer[] refChoices;
+ private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
private int choiceCounter;
private int maxEventChoice;
// Data structure to track the events seen by each state to track cycles (containing all events) for termination
private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
private HashMap<Integer, HashSet<Integer>> stateToEventMap;
// Data structure to analyze field Read/Write accesses and conflicts
- private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
- private Stack<BacktrackPoint> btrckPtsStack; // Stack that stores backtracking points
- private List<IntChoiceFromSet> cgList; // Record CGs for backtracking points
- private HashSet<IntChoiceFromSet> btrckCGSet; // Set that records all the backtrack CGs
- private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
- private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
-
- // Visible operation dependency graph implementation (SPIN paper) related fields
- private int prevChoiceValue;
- private HashMap<Integer, HashSet<Integer>> vodGraphMap; // Visible operation dependency graph (VOD graph)
+ private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
+ private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
+ private ArrayList<BacktrackPoint> backtrackPointList; // Record backtrack points (CG, state Id, and choice)
+ private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
+ private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
+ private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
+ private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
+ private HashMap<Integer, Integer> stateToChoiceCounterMap; // Maps state IDs to the choice counter
// Boolean states
private boolean isBooleanCGFlipped;
+ private boolean isEndOfExecution;
+ // Statistics
+ private int numOfConflicts;
+ private int numOfTransitions;
+
public DPORStateReducer(Config config, JPF jpf) {
verboseMode = config.getBoolean("printout_state_transition", false);
stateReductionMode = config.getBoolean("activate_state_reduction", true);
} else {
out = null;
}
- // DPOR-related
- choices = null;
- refChoices = null;
- choiceCounter = 0;
- maxEventChoice = 0;
- // Cycle tracking
- currVisitedStates = new HashSet<>();
- justVisitedStates = new HashSet<>();
- prevVisitedStates = new HashSet<>();
- stateToEventMap = new HashMap<>();
- // Backtracking
- backtrackMap = new HashMap<>();
- btrckPtsStack = new Stack<>();
- btrckCGSet = new HashSet<>();
- cgList = new ArrayList<>();
- conflictPairMap = new HashMap<>();
- readWriteFieldsMap = new HashMap<>();
- // VOD graph
- prevChoiceValue = -1;
- vodGraphMap = new HashMap<>();
- // Booleans
isBooleanCGFlipped = false;
+ numOfConflicts = 0;
+ numOfTransitions = 0;
+ restorableStateMap = new HashMap<>();
+ initializeStatesVariables();
}
@Override
@Override
public void searchFinished(Search search) {
+ if (stateReductionMode) {
+ // Number of conflicts = first trace + subsequent backtrack points
+ numOfConflicts += 1 + doneBacktrackSet.size();
+ }
if (verboseMode) {
+ out.println("\n==> DEBUG: ----------------------------------- search finished");
+ out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
+ out.println("\n==> DEBUG: Number of conflicts : " + numOfConflicts);
+ out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
}
}
// 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];
+ if (!isEndOfExecution) {
+ // 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];
+ }
+ icsCG.setNewValues(choices);
+ icsCG.reset();
+ // Use a modulo since choiceCounter is going to keep increasing
+ int choiceIndex = choiceCounter % choices.length;
+ icsCG.advance(choices[choiceIndex]);
+ } else {
+ // Set done all CGs while transitioning to a new execution
+ icsCG.setDone();
}
- icsCG.setNewValues(choices);
- icsCG.reset();
- // 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);
}
}
}
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();
-// }
-// }
+ if (currentCG instanceof BooleanChoiceGenerator) {
+ if (!isBooleanCGFlipped) {
+ isBooleanCGFlipped = true;
+ } else {
+ // Number of conflicts = first trace + subsequent backtrack points
+ numOfConflicts = 1 + doneBacktrackSet.size();
+ // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
+ initializeStatesVariables();
+ }
+ }
// Check every choice generated and ensure fair scheduling!
if (currentCG instanceof IntChoiceFromSet) {
IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
+ // If this is a new CG then we need to update data structures
+ resetStatesForNewExecution(icsCG, vm);
// If we don't see a fair scheduling of events/choices then we have to enforce it
- checkAndEnforceFairScheduling(icsCG);
+ fairSchedulingAndBacktrackPoint(icsCG, vm);
// Map state to event
mapStateToEvent(icsCG.getNextChoice());
- // Update the VOD graph always with the latest
- updateVODGraph(icsCG.getNextChoice());
- // Check if we have seen this state or this state contains cycles that involve all events
- if (terminateCurrentExecution()) {
- exploreNextBacktrackSets(icsCG);
+ // Explore the next backtrack point:
+ // 1) if we have seen this state or this state contains cycles that involve all events, and
+ // 2) after the current CG is advanced at least once
+ if (terminateCurrentExecution() && choiceCounter > 0) {
+ exploreNextBacktrackPoints(vm, icsCG);
+ } else {
+ numOfTransitions++;
}
justVisitedStates.clear();
choiceCounter++;
}
+ } else {
+ numOfTransitions++;
}
}
@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 (currentChoice < 0) { // If choice is -1 then skip
- return;
- }
- currentChoice = checkAndAdjustChoice(currentChoice, vm);
- // 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);
+ if (!isEndOfExecution) {
+ // 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 (currentChoice < 0) { // If choice is -1 then skip
+ return;
}
- } 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();
+ currentChoice = checkAndAdjustChoice(currentChoice, vm);
+ // 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)) {
- // Check for conflict (go backward from current choice and get the first conflict)
- for (int eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
- // Check for conflicts with Write fields for both Read and Write instructions
- // Check and record a backtrack set for just once!
- if (isConflictFound(nextInsn, eventCounter, fieldClass) && isNewConflict(currentChoice, eventCounter)) {
- // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
- if (vm.isNewState() || isReachableInVODGraph(currentChoice)) {
+ 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 eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
+ // Check for conflicts with Write fields for both Read and Write instructions
+ // Check and record a backtrack set for just once!
+ if (isConflictFound(nextInsn, eventCounter, currentChoice, fieldClass) &&
+ isNewConflict(currentChoice, eventCounter)) {
createBacktrackingPoint(currentChoice, eventCounter);
}
}
writeSet.put(field, objectId);
}
+ public Set<String> getReadSet() {
+ return readSet.keySet();
+ }
+
+ public Set<String> getWriteSet() {
+ return writeSet.keySet();
+ }
+
public boolean readFieldExists(String field) {
return readSet.containsKey(field);
}
}
}
- // This class compactly stores backtracking points: 1) backtracking ChoiceGenerator, and 2) backtracking choices
+ // This class compactly stores backtrack points: 1) backtrack state ID, and 2) backtracking choices
private class BacktrackPoint {
- private IntChoiceFromSet backtrackCG; // CG to backtrack from
- private Integer[] backtrackChoices; // Choices to set for this backtrack CG
+ private IntChoiceFromSet backtrackCG; // CG at this backtrack point
+ private int stateId; // State at this backtrack point
+ private int choice; // Choice chosen at this backtrack point
- public BacktrackPoint(IntChoiceFromSet cg, Integer[] choices) {
+ public BacktrackPoint(IntChoiceFromSet cg, int stId, int cho) {
backtrackCG = cg;
- backtrackChoices = choices;
+ stateId = stId;
+ choice = cho;
}
- public IntChoiceFromSet getBacktrackCG() {
- return backtrackCG;
+ public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
+
+ public int getStateId() {
+ return stateId;
}
- public Integer[] getBacktrackChoices() {
- return backtrackChoices;
+ public int getChoice() {
+ return choice;
}
}
private final static String JAVA_STRING_LIB = "java.lang.String";
// -- FUNCTIONS
- private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
+ private void fairSchedulingAndBacktrackPoint(IntChoiceFromSet icsCG, VM vm) {
// 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();
icsCG.setChoice(currCGIndex, expectedChoice);
}
}
+ // Record state ID and choice/event as backtrack point
+ int stateId = vm.getStateId();
+ backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex]));
+ // Store restorable state object for this state (always store the latest)
+ RestorableVMState restorableState = vm.getRestorableState();
+ restorableStateMap.put(stateId, restorableState);
+ // Map multiple state IDs to a choice counter
+ for (Integer stId : justVisitedStates) {
+ stateToChoiceCounterMap.put(stId, choiceCounter);
+ }
}
private Integer[] copyChoices(Integer[] choicesToCopy) {
return true;
}
+ private void initializeStatesVariables() {
+ // DPOR-related
+ choices = null;
+ refChoices = null;
+ choiceCounter = 0;
+ maxEventChoice = 0;
+ // Cycle tracking
+ currVisitedStates = new HashSet<>();
+ justVisitedStates = new HashSet<>();
+ prevVisitedStates = new HashSet<>();
+ stateToEventMap = new HashMap<>();
+ // Backtracking
+ backtrackMap = new HashMap<>();
+ backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
+ backtrackPointList = new ArrayList<>();
+ conflictPairMap = new HashMap<>();
+ doneBacktrackSet = new HashSet<>();
+ readWriteFieldsMap = new HashMap<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ // Booleans
+ isEndOfExecution = false;
+ }
+
private void mapStateToEvent(int nextChoiceValue) {
// Update all states with this event/choice
// This means that all past states now see this transition
// 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);
}
+ analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
justVisitedStates.add(stateId);
+ currVisitedStates.add(stateId);
}
// --- Functions related to Read/Write access analysis on shared fields
+ private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList) {
+ // Insert backtrack point to the right state ID
+ LinkedList<Integer[]> backtrackList;
+ if (backtrackMap.containsKey(stateId)) {
+ backtrackList = backtrackMap.get(stateId);
+ } else {
+ backtrackList = new LinkedList<>();
+ backtrackMap.put(stateId, backtrackList);
+ }
+ backtrackList.addFirst(newChoiceList);
+ // Add to priority queue
+ if (!backtrackStateQ.contains(stateId)) {
+ backtrackStateQ.add(stateId);
+ }
+ }
+
// 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
// If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
// for certain method calls in the infrastructure, e.g., eventSince()
int currChoiceInd = currentChoice % refChoices.length;
- int currChoiceFromCG = getCurrentChoice(vm);
+ int currChoiceFromCG = currChoiceInd;
+ ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
+ // This is the main event CG
+ if (currentCG instanceof IntIntervalGenerator) {
+ // This is the interval CG used in device handlers
+ ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
+ int actualEvtNum = ((IntChoiceFromSet) parentCG).getNextChoice();
+ // Find the index of the event/choice in refChoices
+ for (int i = 0; i<refChoices.length; i++) {
+ if (actualEvtNum == refChoices[i]) {
+ currChoiceFromCG = i;
+ break;
+ }
+ }
+ }
if (currChoiceInd != currChoiceFromCG) {
currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
}
Integer[] newChoiceList = new Integer[refChoices.length];
// Put the conflicting event numbers first and reverse the order
int actualCurrCho = currentChoice % refChoices.length;
- int actualConfEvtNum = confEvtNum % refChoices.length;
- newChoiceList[0] = refChoices[actualCurrCho];
- newChoiceList[1] = refChoices[actualConfEvtNum];
+ // We use the actual choices here in case they have been modified/adjusted by the fair scheduling method
+ newChoiceList[0] = choices[actualCurrCho];
+ newChoiceList[1] = backtrackPointList.get(confEvtNum).getChoice();
// Put the rest of the event numbers into the array starting from the minimum to the upper bound
for (int i = 0, j = 2; i < refChoices.length; i++) {
if (refChoices[i] != newChoiceList[0] && refChoices[i] != newChoiceList[1]) {
j++;
}
}
- // Record the backtracking point in the stack as well
- IntChoiceFromSet backtrackCG = cgList.get(confEvtNum);
- BacktrackPoint backtrackPoint = new BacktrackPoint(backtrackCG, newChoiceList);
- btrckPtsStack.push(backtrackPoint);
- // Also record the CG in the set
- btrckCGSet.add(backtrackCG);
+ // Get the backtrack CG for this backtrack point
+ int stateId = backtrackPointList.get(confEvtNum).getStateId();
+ // Check if this trace has been done starting from this state
+ if (isTraceAlreadyConstructed(newChoiceList, stateId)) {
+ return;
+ }
+ addNewBacktrackPoint(stateId, newChoiceList);
}
private boolean excludeThisForItContains(String[] excludedStrings, String className) {
return false;
}
- // TODO: THIS METHOD IS STILL UNTESTED AT THIS POINT
- private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
- // We try to update the CG with a backtrack list if the state has been visited multiple times
- if (icsCG.getNextChoiceIndex() > 0) {
- if (btrckPtsStack.empty()) {
- // TODO: PROBABLY NEED TO DO CONTEXT SWITCHING HERE
- return;
- }
- BacktrackPoint backtrackPoint = btrckPtsStack.pop();
- Integer[] choiceList = backtrackPoint.getBacktrackChoices();
- IntChoiceFromSet backtrackCG = backtrackPoint.getBacktrackCG();
- // Deploy the new choice list for this CG
- backtrackCG.setNewValues(choiceList);
- backtrackCG.reset();
- // Clear unused CGs
- for(IntChoiceFromSet cg : cgList) {
- if (!btrckCGSet.contains(cg)) {
- cg.setDone();
- }
- }
- cgList.clear();
- btrckCGSet.clear();
- // 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 void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
+
+ // Check if we are reaching the end of our execution: no more backtracking points to explore
+ // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
+ if (!backtrackStateQ.isEmpty()) {
+ // Set done all the other backtrack points
+ for (BacktrackPoint backtrackPoint : backtrackPointList) {
+ backtrackPoint.getBacktrackCG().setDone();
+ }
+ // Reset the next backtrack point with the latest state
+ int hiStateId = backtrackStateQ.peek();
+ // Restore the state first if necessary
+ if (vm.getStateId() != hiStateId) {
+ RestorableVMState restorableState = restorableStateMap.get(hiStateId);
+ vm.restoreState(restorableState);
+ }
+ // Set the backtrack CG
+ IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
+ setBacktrackCG(hiStateId, backtrackCG);
+ } else {
+ // Set done this last CG (we save a few rounds)
+ icsCG.setDone();
+ }
+ // Save all the visited states when starting a new execution of trace
+ prevVisitedStates.addAll(currVisitedStates);
+ currVisitedStates.clear();
+ // This marks a transitional period to the new CG
+ isEndOfExecution = true;
}
private ReadWriteSet getReadWriteSet(int currentChoice) {
return rwSet;
}
- private boolean isConflictFound(Instruction nextInsn, int eventCounter, String fieldClass) {
- // Skip if this event does not have any Read/Write set
- if (!readWriteFieldsMap.containsKey(eventCounter)) {
+ private boolean isConflictFound(int eventCounter, int currentChoice) {
+
+ int actualCurrCho = currentChoice % refChoices.length;
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!readWriteFieldsMap.containsKey(eventCounter) ||
+ choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
+ return false;
+ }
+ // Current R/W set
+ ReadWriteSet currRWSet = readWriteFieldsMap.get(currentChoice);
+ // R/W set of choice/event that may have a potential conflict
+ ReadWriteSet evtRWSet = readWriteFieldsMap.get(eventCounter);
+ // Check for conflicts with Read and Write fields for Write instructions
+ Set<String> currWriteSet = currRWSet.getWriteSet();
+ for(String writeField : currWriteSet) {
+ int currObjId = currRWSet.writeFieldObjectId(writeField);
+ if ((evtRWSet.readFieldExists(writeField) && evtRWSet.readFieldObjectId(writeField) == currObjId) ||
+ (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId)) {
+ return true;
+ }
+ }
+ // Check for conflicts with Write fields for Read instructions
+ Set<String> currReadSet = currRWSet.getReadSet();
+ for(String readField : currReadSet) {
+ int currObjId = currRWSet.readFieldObjectId(readField);
+ if (evtRWSet.writeFieldExists(readField) && evtRWSet.writeFieldObjectId(readField) == currObjId) {
+ return true;
+ }
+ }
+ // Return false if no conflict is found
+ return false;
+ }
+
+ private boolean isConflictFound(Instruction nextInsn, int eventCounter, int currentChoice, String fieldClass) {
+
+ int actualCurrCho = currentChoice % refChoices.length;
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!readWriteFieldsMap.containsKey(eventCounter) ||
+ choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
return false;
}
ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
return true;
}
- // --- Functions related to the visible operation dependency graph implementation discussed in the SPIN paper
-
- // This method checks whether a choice is reachable in the VOD graph from a reference choice (BFS algorithm)
- //private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
- private boolean isReachableInVODGraph(int currentChoice) {
- // Extract previous and current events
- int choiceIndex = currentChoice % refChoices.length;
- int currEvent = refChoices[choiceIndex];
- int prevEvent = refChoices[choiceIndex - 1];
- // Record visited choices as we search in the graph
- HashSet<Integer> visitedChoice = new HashSet<>();
- visitedChoice.add(prevEvent);
- LinkedList<Integer> nodesToVisit = new LinkedList<>();
- // If the state doesn't advance as the threads/sub-programs are executed (basically there is no new state),
- // there is a chance that the graph doesn't have new nodes---thus this check will return a null.
- if (vodGraphMap.containsKey(prevEvent)) {
- nodesToVisit.addAll(vodGraphMap.get(prevEvent));
- while(!nodesToVisit.isEmpty()) {
- int choice = nodesToVisit.getFirst();
- if (choice == currEvent) {
- return true;
- }
- if (visitedChoice.contains(choice)) { // If there is a loop then we don't find it
- return false;
- }
- // Continue searching
- visitedChoice.add(choice);
- HashSet<Integer> choiceNextNodes = vodGraphMap.get(choice);
- if (choiceNextNodes != null) {
- // Add only if there is a mapping for next nodes
- for (Integer nextNode : choiceNextNodes) {
- // Skip cycles
- if (nextNode == choice) {
- continue;
- }
- nodesToVisit.addLast(nextNode);
- }
- }
- }
+ private boolean isTraceAlreadyConstructed(Integer[] choiceList, int stateId) {
+ // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
+ // TODO: THIS IS AN OPTIMIZATION!
+ // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
+ // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
+ // The second time this event 1 is explored, it will generate the same state as the first one
+ StringBuilder sb = new StringBuilder();
+ sb.append(stateId);
+ sb.append(':');
+ sb.append(choiceList[0]);
+ // Check if the trace has been constructed as a backtrack point for this state
+ if (doneBacktrackSet.contains(sb.toString())) {
+ return true;
}
+ doneBacktrackSet.add(sb.toString());
return false;
}
- private void updateVODGraph(int currChoiceValue) {
- // Update the graph when we have the current choice value
- HashSet<Integer> choiceSet;
- if (vodGraphMap.containsKey(prevChoiceValue)) {
- // If the key already exists, just retrieve it
- choiceSet = vodGraphMap.get(prevChoiceValue);
- } else {
- // Create a new entry
- choiceSet = new HashSet<>();
- vodGraphMap.put(prevChoiceValue, choiceSet);
+ private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
+ if (choices == null || choices != icsCG.getAllChoices()) {
+ // Reset state variables
+ choiceCounter = 0;
+ choices = icsCG.getAllChoices();
+ refChoices = copyChoices(choices);
+ // Clearing data structures
+ conflictPairMap.clear();
+ readWriteFieldsMap.clear();
+ stateToEventMap.clear();
+ isEndOfExecution = false;
+ backtrackPointList.clear();
+ }
+ }
+
+ private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
+ // Set a backtrack CG based on a state ID
+ LinkedList<Integer[]> backtrackChoices = backtrackMap.get(stateId);
+ backtrackCG.setNewValues(backtrackChoices.removeLast()); // Get the last from the queue
+ backtrackCG.setStateId(stateId);
+ backtrackCG.reset();
+ // Remove from the queue if we don't have more backtrack points for that state
+ if (backtrackChoices.isEmpty()) {
+ backtrackMap.remove(stateId);
+ backtrackStateQ.remove(stateId);
+ }
+ }
+
+ // --- Functions related to the reachability analysis when there is a state match
+
+ // We use backtrackPointsList to analyze the reachable states/events when there is a state match:
+ // 1) Whenever there is state match, there is a cycle of events
+ // 2) We need to analyze and find conflicts for the reachable choices/events in the cycle
+ // 3) Then we create a new backtrack point for every new conflict
+ private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
+ // Perform this analysis only when:
+ // 1) there is a state match,
+ // 2) this is not during a switch to a new execution,
+ // 3) at least 2 choices/events have been explored (choiceCounter > 1),
+ // 4) the matched state has been encountered in the current execution, and
+ // 5) state > 0 (state 0 is for boolean CG)
+ if (!vm.isNewState() && !isEndOfExecution && choiceCounter > 1 &&
+ currVisitedStates.contains(stateId) && (stateId > 0)) {
+ // Find the choice/event that marks the start of this cycle: first choice we explore for conflicts
+ int conflictChoice = stateToChoiceCounterMap.get(stateId);
+ int currentChoice = choiceCounter - 1;
+ // Find conflicts between choices/events in this cycle (we scan forward in the cycle, not backward)
+ while (conflictChoice < currentChoice) {
+ for (int eventCounter = conflictChoice + 1; eventCounter <= currentChoice; eventCounter++) {
+ if (isConflictFound(eventCounter, conflictChoice) && isNewConflict(conflictChoice, eventCounter)) {
+ createBacktrackingPoint(conflictChoice, eventCounter);
+ }
+ }
+ conflictChoice++;
+ }
}
- choiceSet.add(currChoiceValue);
- prevChoiceValue = currChoiceValue;
}
}
projects / jpf-core.git / blobdiff