// TODO: Fix for Groovy's model-checking
// TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
/**
- * simple tool to log state changes
+ * Simple tool to log state changes.
+ *
+ * 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.
*/
public class StateReducer extends ListenerAdapter {
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;
// 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)
+ private HashMap<Integer, HashSet<Integer>> vodGraphMap;
+ // 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
+ // Current state
+ private int stateId;
+ // 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);
id = 0;
transition = null;
isBooleanCGFlipped = false;
+ vodGraphMap = new HashMap<>();
+ stateId = -1;
+ 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();
}
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 - 1);
+ icsCG.advance(choices[choiceIndex]);
+ if (choiceIndex == 0) {
+ resetReadWriteAnalysis();
+ }
+ return icsCG;
+ }
+
+ 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
+ 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);
+ }
+ IntChoiceFromSet setCG = setNewCG(icsCG);
+ cgMap.put(setCG, choices[choiceCounter]);
+ } else {
+ // We repeat the same trace if a state match is not found yet
+ IntChoiceFromSet setCG = setNewCG(icsCG);
+ unusedCG.add(setCG);
+ }
+ choiceCounter++;
+ }
+
@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)
+ // Set new CGs to done so that the search algorithm explores the existing CGs
icsCG.setDone();
}
}
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();
}
}
+ // Set done every CG in the unused CG set
+ for (IntChoiceFromSet cg : unusedCG) {
+ cg.setDone();
+ }
+ unusedCG.clear();
+ 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 updateChoices(IntChoiceFromSet icsCG) {
+ if (choices == null || choices != icsCG.getAllChoices()) {
+ currCG = icsCG;
+ choices = icsCG.getAllChoices();
+ // Reset a few things for the sub-graph
+ resetReadWriteAnalysis();
+ choiceCounter = 0;
+ }
+ }
+
+ private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
+ // Traverse the sub-graphs
+ if (isResetAfterAnalysis) {
+ // Advance choice counter for sub-graphs
+ choiceCounter++;
+ // 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)) {
+ 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();
+ }
+ 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;
+ }
}
@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) {
- 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;
+ updateChoices(icsCG);
+ // Check if we have seen this state or this state contains cycles that involve all events
+ if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
+ exploreNextBacktrackSets(icsCG);
}
+ // Update the VOD graph always with the latest
+ updateVODGraph(icsCG.getNextChoice());
}
}
}
+ 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);
+ }
+ choiceSet.add(currChoiceValue);
+ prevChoiceValue = currChoiceValue;
+ }
+
+ private void mapStateToEvent(Search search) {
+ // 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)
+ stateId = search.getStateId();
+ currVisitedStates.add(stateId);
+ mapStateToEvent(search);
+ }
+ }
+
@Override
public void stateAdvanced(Search search) {
if (debugMode) {
out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
" which is " + detail + " Transition: " + transition + "\n");
}
+ 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
// 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;
return false;
}
+ // This method checks whether a choice is reachable in the VOD graph from a reference choice
+ // This is a BFS search
+ private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
+ // Record visited choices as we search in the graph
+ HashSet<Integer> visitedChoice = new HashSet<>();
+ visitedChoice.add(referenceChoice);
+ 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(referenceChoice)) {
+ nodesToVisit.addAll(vodGraphMap.get(referenceChoice));
+ while(!nodesToVisit.isEmpty()) {
+ int currChoice = nodesToVisit.getFirst();
+ if (currChoice == checkedChoice) {
+ return true;
+ }
+ if (visitedChoice.contains(currChoice)) {
+ // If there is a loop then we don't find it
+ return false;
+ }
+ // Continue searching
+ visitedChoice.add(currChoice);
+ HashSet<Integer> currChoiceNextNodes = vodGraphMap.get(currChoice);
+ 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);
+ }
+ }
+ }
+ }
+ return false;
+ }
+
@Override
public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
if (stateReductionMode) {
if (isInitialized) {
- if (choiceCounter > choices.length - 1) {
+ int currentChoice = (choiceCounter % (choices.length - 1)) - 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
String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
// We don't care about libraries
if (!isFieldExcluded(fieldClass)) {
- // For the main graph we go down to 0, but for subgraph, we only go down to 1 since 0 contains
- // the reversed event
-// int end = !isResetAfterAnalysis ? 0 : choiceListStartIndexMap.get(choices);
// Check for conflict (go backward from currentChoice and get the first conflict)
// If the current event has conflicts with multiple events, then these will be detected
// one by one as this recursively checks backward when backtrack set is revisited and executed.
-// for (int eventNumber = currentChoice - 1; eventNumber >= end; eventNumber--) {
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])) {
// We do not record and service the same backtrack pair/point twice!
// If it has been serviced before, we just skip this
if (recordConflictPair(currentChoice, eventNumber)) {
- createBacktrackChoiceList(currentChoice, eventNumber);
- // Break if a conflict is found!
- break;
+ // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
+ if (vm.isNewState() || isReachableInVODGraph(choices[currentChoice], choices[currentChoice-1])) {
+ createBacktrackChoiceList(currentChoice, eventNumber);
+ // Break if a conflict is found!
+ break;
+ }
}
}
}
projects / jpf-core.git / blobdiff