// 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
+ 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
// Visible operation dependency graph implementation (SPIN paper) related fields
private int prevChoiceValue;
// Boolean states
private boolean isBooleanCGFlipped;
+ private boolean isEndOfExecution;
public DPORStateReducer(Config config, JPF jpf) {
verboseMode = config.getBoolean("printout_state_transition", false);
} 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;
+ restorableStateMap = new HashMap<>();
+ initializeStatesVariables();
}
@Override
// 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 {
+ // 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);
+ exploreNextBacktrackPoints(vm, 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 (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)) {
- createBacktrackingPoint(currentChoice, eventCounter);
+ 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)) {
+ // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
+ if (vm.isNewState() || isReachableInVODGraph(currentChoice)) {
+ createBacktrackingPoint(currentChoice, eventCounter);
+ }
}
}
}
}
}
- // 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
+ backtrackPointList.add(new BacktrackPoint(icsCG, vm.getStateId(), refChoices[choiceIndex]));
}
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<>();
+ // VOD graph
+ prevChoiceValue = -1;
+ vodGraphMap = 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
stateToEventMap.put(stateId, eventSet);
}
justVisitedStates.add(stateId);
+ // Store restorable state object for this state (always store the latest)
+ RestorableVMState restorableState = search.getVM().getRestorableState();
+ restorableStateMap.put(stateId, restorableState);
}
// --- 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 = 0;
+ ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
+ // This is the main event CG
+ if (currentCG instanceof IntChoiceFromSet) {
+ currChoiceFromCG = currChoiceInd;
+ } else {
+ // This is the interval CG used in device handlers
+ ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
+ currChoiceFromCG = ((IntChoiceFromSet) parentCG).getNextChoiceIndex();
+ }
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;
+ }
+ //BacktrackPoint backtrackPoint = new BacktrackPoint(backtrackCG, newChoiceList);
+ 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();
+ private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
+
+ // We can start exploring the next backtrack point after the current CG is advanced at least once
+ if (choiceCounter > 0) {
+ // 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();
}
- 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();
+ // This marks a transitional period to the new CG
+ isEndOfExecution = true;
}
}
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(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;
}
+ 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 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 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 currentChoice) {
// Extract previous and current events
int choiceIndex = currentChoice % refChoices.length;
+ int prevChoIndex = (currentChoice - 1) % refChoices.length;
int currEvent = refChoices[choiceIndex];
- int prevEvent = refChoices[choiceIndex - 1];
+ int prevEvent = refChoices[prevChoIndex];
// Record visited choices as we search in the graph
HashSet<Integer> visitedChoice = new HashSet<>();
visitedChoice.add(prevEvent);
projects / jpf-core.git / blobdiff