2 * Copyright (C) 2014, United States Government, as represented by the
3 * Administrator of the National Aeronautics and Space Administration.
6 * The Java Pathfinder core (jpf-core) platform is licensed under the
7 * Apache License, Version 2.0 (the "License"); you may not use this file except
8 * in compliance with the License. You may obtain a copy of the License at
10 * http://www.apache.org/licenses/LICENSE-2.0.
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
18 package gov.nasa.jpf.listener;
20 import gov.nasa.jpf.Config;
21 import gov.nasa.jpf.JPF;
22 import gov.nasa.jpf.ListenerAdapter;
23 import gov.nasa.jpf.jvm.bytecode.INVOKEINTERFACE;
24 import gov.nasa.jpf.jvm.bytecode.JVMFieldInstruction;
25 import gov.nasa.jpf.report.Publisher;
26 import gov.nasa.jpf.search.Search;
27 import gov.nasa.jpf.vm.*;
28 import gov.nasa.jpf.vm.bytecode.ReadInstruction;
29 import gov.nasa.jpf.vm.bytecode.WriteInstruction;
30 import gov.nasa.jpf.vm.choice.IntChoiceFromSet;
31 import gov.nasa.jpf.vm.choice.IntIntervalGenerator;
33 import java.io.FileWriter;
34 import java.io.IOException;
35 import java.io.PrintWriter;
37 import java.util.logging.Logger;
40 * This a DPOR implementation for event-driven applications with loops that create cycles of state matching
41 * In this new DPOR algorithm/implementation, each run is terminated iff:
42 * - we find a state that matches a state in a previous run, or
43 * - we have a matched state in the current run that consists of cycles that contain all choices/events.
45 public class DPORStateReducerWithSummary extends ListenerAdapter {
47 // Information printout fields for verbose mode
48 private boolean verboseMode;
49 private boolean stateReductionMode;
50 private final PrintWriter out;
51 private PrintWriter fileWriter;
52 private String detail;
55 private Transition transition;
57 // DPOR-related fields
59 private Integer[] choices;
60 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
61 private int choiceCounter;
62 private int maxEventChoice;
63 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
64 private HashMap<Integer,Integer> currVisitedStates; // States visited in the current execution (maps to frequency)
65 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
66 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
67 private HashSet<ClassInfo> nonRelevantClasses;// Class info objects of non-relevant classes
68 private HashSet<FieldInfo> nonRelevantFields; // Field info objects of non-relevant fields
69 private HashSet<FieldInfo> relevantFields; // Field info objects of relevant fields
70 private HashMap<Integer, HashSet<Integer>> stateToEventMap; // Map state ID to events
71 // Data structure to analyze field Read/Write accesses and conflicts
72 private HashMap<Integer, LinkedList<BacktrackExecution>> backtrackMap; // Track created backtracking points
73 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
74 private Execution currentExecution; // Holds the information about the current execution
75 private HashMap<Integer, HashSet<Integer>> doneBacktrackMap; // Record state ID and trace already constructed
76 private MainSummary mainSummary; // Main summary (M) for state ID, event, and R/W set
77 private HashMap<Integer, PredecessorInfo> stateToPredInfo; // Predecessor info indexed by state ID
78 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
79 private RGraph rGraph; // R-Graph for past executions
82 private boolean isBooleanCGFlipped;
83 private boolean isEndOfExecution;
84 private boolean isNotCheckedForEventsYet;
87 private int numOfTransitions;
88 private HashMap<Integer, HashSet<Integer>> stateToUniqueTransMap;
90 public DPORStateReducerWithSummary(Config config, JPF jpf) {
91 verboseMode = config.getBoolean("printout_state_transition", false);
92 stateReductionMode = config.getBoolean("activate_state_reduction", true);
94 out = new PrintWriter(System.out, true);
98 String outputFile = config.getString("file_output");
99 if (!outputFile.isEmpty()) {
101 fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
102 } catch (IOException e) {
105 isBooleanCGFlipped = false;
106 isNotCheckedForEventsYet = true;
107 mainSummary = new MainSummary();
108 numOfTransitions = 0;
109 nonRelevantClasses = new HashSet<>();
110 nonRelevantFields = new HashSet<>();
111 relevantFields = new HashSet<>();
112 restorableStateMap = new HashMap<>();
113 stateToPredInfo = new HashMap<>();
114 stateToUniqueTransMap = new HashMap<>();
115 initializeStatesVariables();
119 public void stateRestored(Search search) {
121 id = search.getStateId();
122 depth = search.getDepth();
123 transition = search.getTransition();
125 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
126 " and depth: " + depth + "\n");
131 public void searchStarted(Search search) {
133 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
138 public void stateAdvanced(Search search) {
140 id = search.getStateId();
141 depth = search.getDepth();
142 transition = search.getTransition();
143 if (search.isNewState()) {
149 if (search.isEndState()) {
150 out.println("\n==> DEBUG: This is the last state!\n");
153 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
154 " which is " + detail + " Transition: " + transition + "\n");
156 if (stateReductionMode) {
157 updateStateInfo(search);
162 public void stateBacktracked(Search search) {
164 id = search.getStateId();
165 depth = search.getDepth();
166 transition = search.getTransition();
169 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
170 " and depth: " + depth + "\n");
172 if (stateReductionMode) {
173 updateStateInfo(search);
177 static Logger log = JPF.getLogger("report");
180 public void searchFinished(Search search) {
182 int summaryOfUniqueTransitions = summarizeUniqueTransitions();
183 out.println("\n==> DEBUG: ----------------------------------- search finished");
184 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
185 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
186 out.println("\n==> DEBUG: Number of unique transitions (DPOR) : " + summaryOfUniqueTransitions);
187 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
189 fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
190 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
191 fileWriter.println("==> DEBUG: Number of unique transitions (DPOR) : " + summaryOfUniqueTransitions);
192 fileWriter.println();
198 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
199 if (isNotCheckedForEventsYet) {
200 // Check if this benchmark has no events
201 if (nextCG instanceof IntChoiceFromSet) {
202 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
203 Integer[] cgChoices = icsCG.getAllChoices();
204 if (cgChoices.length == 2 && cgChoices[0] == 0 && cgChoices[1] == -1) {
205 // This means the benchmark only has 2 choices, i.e., 0 and -1 which means that it has no events
206 stateReductionMode = false;
208 isNotCheckedForEventsYet = false;
211 if (stateReductionMode) {
212 // Initialize with necessary information from the CG
213 if (nextCG instanceof IntChoiceFromSet) {
214 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
215 // Tell JPF that we are performing DPOR
217 if (!isEndOfExecution) {
218 // Check if CG has been initialized, otherwise initialize it
219 Integer[] cgChoices = icsCG.getAllChoices();
220 // Record the events (from choices)
221 if (choices == null) {
223 // Make a copy of choices as reference
224 refChoices = copyChoices(choices);
225 // Record the max event choice (the last element of the choice array)
226 maxEventChoice = choices[choices.length - 1];
228 icsCG.setNewValues(choices);
230 // Use a modulo since choiceCounter is going to keep increasing
231 int choiceIndex = choiceCounter % choices.length;
232 icsCG.advance(choices[choiceIndex]);
234 // Set done all CGs while transitioning to a new execution
242 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
243 if (stateReductionMode) {
244 // Check the boolean CG and if it is flipped, we are resetting the analysis
245 if (currentCG instanceof BooleanChoiceGenerator) {
246 if (!isBooleanCGFlipped) {
247 isBooleanCGFlipped = true;
249 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
250 initializeStatesVariables();
253 // Check every choice generated and ensure fair scheduling!
254 if (currentCG instanceof IntChoiceFromSet) {
255 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
256 // If this is a new CG then we need to update data structures
257 resetStatesForNewExecution(icsCG, vm);
258 // If we don't see a fair scheduling of events/choices then we have to enforce it
259 ensureFairSchedulingAndSetupTransition(icsCG, vm);
260 // Update backtrack set of an executed event (transition): one transition before this one
261 updateBacktrackSet(currentExecution, choiceCounter - 1);
262 // Explore the next backtrack point:
263 // 1) if we have seen this state or this state contains cycles that involve all events, and
264 // 2) after the current CG is advanced at least once
265 if (choiceCounter > 0 && terminateCurrentExecution()) {
266 exploreNextBacktrackPoints(vm, icsCG);
268 // We only count IntChoiceFromSet CGs
270 countUniqueTransitions(vm.getStateId(), icsCG.getNextChoice());
272 // Map state to event
273 mapStateToEvent(icsCG.getNextChoice());
274 justVisitedStates.clear();
278 // We only count IntChoiceFromSet CGs
279 if (currentCG instanceof IntChoiceFromSet) {
286 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
287 if (stateReductionMode) {
288 if (!isEndOfExecution) {
289 // Has to be initialized and it is a integer CG
290 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
291 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
292 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
293 if (currentChoice < 0) { // If choice is -1 then skip
296 currentChoice = checkAndAdjustChoice(currentChoice, vm);
297 // Record accesses from executed instructions
298 if (executedInsn instanceof JVMFieldInstruction) {
299 // We don't care about libraries
300 if (!isFieldExcluded(executedInsn)) {
301 analyzeReadWriteAccesses(executedInsn, currentChoice);
303 } else if (executedInsn instanceof INVOKEINTERFACE) {
304 // Handle the read/write accesses that occur through iterators
305 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
317 // This class compactly stores backtrack execution:
318 // 1) backtrack choice list, and
319 // 2) first backtrack point (linking with predecessor execution)
320 private class BacktrackExecution {
321 private Integer[] choiceList;
322 private TransitionEvent firstTransition;
324 public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
325 choiceList = choList;
326 firstTransition = fTransition;
329 public Integer[] getChoiceList() {
333 public TransitionEvent getFirstTransition() {
334 return firstTransition;
338 // This class stores a representation of an execution
339 // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
340 // TODO: We basically need to keep track of:
341 // TODO: (1) last read/write access to each memory location
342 // TODO: (2) last state with two or more incoming events/transitions
343 private class Execution {
344 private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
345 private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
346 private boolean isNew; // Track if this is the first time it is accessed
347 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
350 cgToChoiceMap = new HashMap<>();
351 executionTrace = new ArrayList<>();
353 readWriteFieldsMap = new HashMap<>();
356 public void addTransition(TransitionEvent newBacktrackPoint) {
357 executionTrace.add(newBacktrackPoint);
360 public void clearCGToChoiceMap() {
361 cgToChoiceMap = null;
364 public int getChoiceFromCG(IntChoiceFromSet icsCG) {
365 return cgToChoiceMap.get(icsCG);
368 public ArrayList<TransitionEvent> getExecutionTrace() {
369 return executionTrace;
372 public TransitionEvent getFirstTransition() {
373 return executionTrace.get(0);
376 public TransitionEvent getLastTransition() {
377 return executionTrace.get(executionTrace.size() - 1);
380 public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
381 return readWriteFieldsMap;
384 public boolean isNew() {
386 // Right after this is accessed, it is no longer new
393 public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
394 cgToChoiceMap.put(icsCG, choice);
398 // This class compactly stores a predecessor
399 // 1) a predecessor execution
400 // 2) the predecessor choice in that predecessor execution
401 private class Predecessor {
402 private int choice; // Predecessor choice
403 private Execution execution; // Predecessor execution
405 public Predecessor(int predChoice, Execution predExec) {
407 execution = predExec;
410 public int getChoice() {
414 public Execution getExecution() {
419 // This class represents a R-Graph (in the paper it is a state transition graph R)
420 // This implementation stores reachable transitions from and connects with past executions
421 private class RGraph {
422 private int hiStateId; // Maximum state Id
423 private HashMap<Integer, HashSet<TransitionEvent>> graph; // Reachable transitions from past executions
427 graph = new HashMap<>();
430 public void addReachableTransition(int stateId, TransitionEvent transition) {
431 HashSet<TransitionEvent> transitionSet;
432 if (graph.containsKey(stateId)) {
433 transitionSet = graph.get(stateId);
435 transitionSet = new HashSet<>();
436 graph.put(stateId, transitionSet);
438 // Insert into the set if it does not contain it yet
439 if (!transitionSet.contains(transition)) {
440 transitionSet.add(transition);
442 // Update highest state ID
443 if (hiStateId < stateId) {
448 public HashSet<TransitionEvent> getReachableTransitionsAtState(int stateId) {
449 if (!graph.containsKey(stateId)) {
450 // This is a loop from a transition to itself, so just return the current transition
451 HashSet<TransitionEvent> transitionSet = new HashSet<>();
452 transitionSet.add(currentExecution.getLastTransition());
453 return transitionSet;
455 return graph.get(stateId);
458 public HashSet<TransitionEvent> getReachableTransitions(int stateId) {
459 HashSet<TransitionEvent> reachableTransitions = new HashSet<>();
460 // All transitions from states higher than the given state ID (until the highest state ID) are reachable
461 for(int stId = stateId; stId <= hiStateId; stId++) {
462 // We might encounter state IDs from the first round of Boolean CG
463 // The second round of Boolean CG should consider these new states
464 if (graph.containsKey(stId)) {
465 reachableTransitions.addAll(graph.get(stId));
468 return reachableTransitions;
472 // This class compactly stores Read and Write field sets
473 // We store the field name and its object ID
474 // Sharing the same field means the same field name and object ID
475 private class ReadWriteSet {
476 private HashMap<String, Integer> readMap;
477 private HashMap<String, Integer> writeMap;
479 public ReadWriteSet() {
480 readMap = new HashMap<>();
481 writeMap = new HashMap<>();
484 public void addReadField(String field, int objectId) {
485 readMap.put(field, objectId);
488 public void addWriteField(String field, int objectId) {
489 writeMap.put(field, objectId);
492 public void removeReadField(String field) {
493 readMap.remove(field);
496 public void removeWriteField(String field) {
497 writeMap.remove(field);
500 public boolean isEmpty() {
501 return readMap.isEmpty() && writeMap.isEmpty();
504 public ReadWriteSet getCopy() {
505 ReadWriteSet copyRWSet = new ReadWriteSet();
506 // Copy the maps in the set into the new object copy
507 copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
508 copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
512 public Set<String> getReadSet() {
513 return readMap.keySet();
516 public Set<String> getWriteSet() {
517 return writeMap.keySet();
520 public boolean readFieldExists(String field) {
521 return readMap.containsKey(field);
524 public boolean writeFieldExists(String field) {
525 return writeMap.containsKey(field);
528 public int readFieldObjectId(String field) {
529 return readMap.get(field);
532 public int writeFieldObjectId(String field) {
533 return writeMap.get(field);
536 private HashMap<String, Integer> getReadMap() {
540 private HashMap<String, Integer> getWriteMap() {
544 private void setReadMap(HashMap<String, Integer> rMap) {
548 private void setWriteMap(HashMap<String, Integer> wMap) {
553 // This class is a representation of a state.
554 // It stores the predecessors to a state.
555 // TODO: We also have stateToEventMap, restorableStateMap, and doneBacktrackMap that has state Id as HashMap key.
556 private class PredecessorInfo {
557 private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
558 private HashMap<Execution, HashSet<Integer>> recordedPredecessors;
559 // Memorize event and choice number to not record them twice
561 public PredecessorInfo() {
562 predecessors = new HashSet<>();
563 recordedPredecessors = new HashMap<>();
566 public HashSet<Predecessor> getPredecessors() {
570 private boolean isRecordedPredecessor(Execution execution, int choice) {
571 // See if we have recorded this predecessor earlier
572 HashSet<Integer> recordedChoices;
573 if (recordedPredecessors.containsKey(execution)) {
574 recordedChoices = recordedPredecessors.get(execution);
575 if (recordedChoices.contains(choice)) {
579 recordedChoices = new HashSet<>();
580 recordedPredecessors.put(execution, recordedChoices);
582 // Record the choice if we haven't seen it
583 recordedChoices.add(choice);
588 public void recordPredecessor(Execution execution, int choice) {
589 if (!isRecordedPredecessor(execution, choice)) {
590 predecessors.add(new Predecessor(choice, execution));
595 // This class compactly stores transitions:
599 // 4) predecessors (for backward DFS).
600 private class TransitionEvent {
601 private int choice; // Choice chosen at this transition
602 private int choiceCounter; // Choice counter at this transition
603 private Execution execution; // The execution where this transition belongs
604 private int stateId; // State at this transition
605 private IntChoiceFromSet transitionCG; // CG at this transition
607 public TransitionEvent() {
615 public int getChoice() {
619 public int getChoiceCounter() {
620 return choiceCounter;
623 public Execution getExecution() {
627 public int getStateId() {
631 public IntChoiceFromSet getTransitionCG() { return transitionCG; }
633 public void setChoice(int cho) {
637 public void setChoiceCounter(int choCounter) {
638 choiceCounter = choCounter;
641 public void setExecution(Execution exec) {
645 public void setStateId(int stId) {
649 public void setTransitionCG(IntChoiceFromSet cg) {
654 // -- PRIVATE CLASSES RELATED TO SUMMARY
655 // This class stores the main summary of states
656 // 1) Main mapping between state ID and state summary
657 // 2) State summary is a mapping between events (i.e., event choices) and their respective R/W sets
658 private class MainSummary {
659 private HashMap<Integer, HashMap<Integer, ReadWriteSet>> mainSummary;
661 public MainSummary() {
662 mainSummary = new HashMap<>();
665 public Set<Integer> getEventChoicesAtStateId(int stateId) {
666 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
667 // Return a new set since this might get updated concurrently
668 return new HashSet<>(stateSummary.keySet());
671 public ReadWriteSet getRWSetForEventChoiceAtState(int eventChoice, int stateId) {
672 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
673 return stateSummary.get(eventChoice);
676 public Set<Integer> getStateIds() {
677 return mainSummary.keySet();
680 private ReadWriteSet performUnion(ReadWriteSet recordedRWSet, ReadWriteSet rwSet) {
681 // Combine the same write accesses and record in the recordedRWSet
682 HashMap<String, Integer> recordedWriteMap = recordedRWSet.getWriteMap();
683 HashMap<String, Integer> writeMap = rwSet.getWriteMap();
684 for(Map.Entry<String, Integer> entry : recordedWriteMap.entrySet()) {
685 String writeField = entry.getKey();
686 // Remove the entry from rwSet if both field and object ID are the same
687 if (writeMap.containsKey(writeField) &&
688 (writeMap.get(writeField).equals(recordedWriteMap.get(writeField)))) {
689 writeMap.remove(writeField);
692 // Then add the rest (fields in rwSet but not in recordedRWSet)
693 // into the recorded map because these will be traversed
694 recordedWriteMap.putAll(writeMap);
695 // Combine the same read accesses and record in the recordedRWSet
696 HashMap<String, Integer> recordedReadMap = recordedRWSet.getReadMap();
697 HashMap<String, Integer> readMap = rwSet.getReadMap();
698 for(Map.Entry<String, Integer> entry : recordedReadMap.entrySet()) {
699 String readField = entry.getKey();
700 // Remove the entry from rwSet if both field and object ID are the same
701 if (readMap.containsKey(readField) &&
702 (readMap.get(readField).equals(recordedReadMap.get(readField)))) {
703 readMap.remove(readField);
706 // Then add the rest (fields in rwSet but not in recordedRWSet)
707 // into the recorded map because these will be traversed
708 recordedReadMap.putAll(readMap);
713 public ReadWriteSet updateStateSummary(int stateId, int eventChoice, ReadWriteSet rwSet) {
714 // If the state Id has not existed, insert the StateSummary object
715 // If the state Id has existed, find the event choice:
716 // 1) If the event choice has not existed, insert the ReadWriteSet object
717 // 2) If the event choice has existed, perform union between the two ReadWriteSet objects
718 if (!rwSet.isEmpty()) {
719 HashMap<Integer, ReadWriteSet> stateSummary;
720 if (!mainSummary.containsKey(stateId)) {
721 stateSummary = new HashMap<>();
722 stateSummary.put(eventChoice, rwSet.getCopy());
723 mainSummary.put(stateId, stateSummary);
725 stateSummary = mainSummary.get(stateId);
726 if (!stateSummary.containsKey(eventChoice)) {
727 stateSummary.put(eventChoice, rwSet.getCopy());
729 rwSet = performUnion(stateSummary.get(eventChoice), rwSet);
738 private final static String DO_CALL_METHOD = "doCall";
739 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
740 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
741 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
742 // Groovy library created fields
743 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
745 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
746 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
747 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
748 // Java and Groovy libraries
749 { "java", "org", "sun", "com", "gov", "groovy"};
750 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
751 private final static String GET_PROPERTY_METHOD =
752 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
753 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
754 private final static String JAVA_INTEGER = "int";
755 private final static String JAVA_STRING_LIB = "java.lang.String";
758 private Integer[] copyChoices(Integer[] choicesToCopy) {
760 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
761 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
762 return copyOfChoices;
765 private void ensureFairSchedulingAndSetupTransition(IntChoiceFromSet icsCG, VM vm) {
766 // Check the next choice and if the value is not the same as the expected then force the expected value
767 int choiceIndex = choiceCounter % refChoices.length;
768 int nextChoice = icsCG.getNextChoice();
769 if (refChoices[choiceIndex] != nextChoice) {
770 int expectedChoice = refChoices[choiceIndex];
771 int currCGIndex = icsCG.getNextChoiceIndex();
772 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
773 icsCG.setChoice(currCGIndex, expectedChoice);
776 // Get state ID and associate it with this transition
777 int stateId = vm.getStateId();
778 TransitionEvent transition = setupTransition(icsCG, stateId, choiceIndex);
779 // Add new transition to the current execution and map it in R-Graph
780 for (Integer stId : justVisitedStates) { // Map this transition to all the previously passed states
781 rGraph.addReachableTransition(stId, transition);
783 currentExecution.mapCGToChoice(icsCG, choiceCounter);
784 // Store restorable state object for this state (always store the latest)
785 if (!restorableStateMap.containsKey(stateId)) {
786 RestorableVMState restorableState = vm.getRestorableState();
787 restorableStateMap.put(stateId, restorableState);
791 private TransitionEvent setupTransition(IntChoiceFromSet icsCG, int stateId, int choiceIndex) {
792 // Get a new transition
793 TransitionEvent transition;
794 if (currentExecution.isNew()) {
795 // We need to handle the first transition differently because this has a predecessor execution
796 transition = currentExecution.getFirstTransition();
798 transition = new TransitionEvent();
799 currentExecution.addTransition(transition);
800 addPredecessors(stateId);
802 transition.setExecution(currentExecution);
803 transition.setTransitionCG(icsCG);
804 transition.setStateId(stateId);
805 transition.setChoice(refChoices[choiceIndex]);
806 transition.setChoiceCounter(choiceCounter);
811 // --- Functions related to statistics counting
812 // Count unique state IDs
813 private void countUniqueTransitions(int stateId, int nextChoiceValue) {
814 HashSet<Integer> events;
815 // Get the set of events
816 if (!stateToUniqueTransMap.containsKey(stateId)) {
817 events = new HashSet<>();
818 stateToUniqueTransMap.put(stateId, events);
820 events = stateToUniqueTransMap.get(stateId);
823 if (!events.contains(nextChoiceValue)) {
824 events.add(nextChoiceValue);
828 // Summarize unique state IDs
829 private int summarizeUniqueTransitions() {
830 // Just count the set size of each of entry map and sum them up
831 int numOfUniqueTransitions = 0;
832 for (Map.Entry<Integer,HashSet<Integer>> entry : stateToUniqueTransMap.entrySet()) {
833 numOfUniqueTransitions = numOfUniqueTransitions + entry.getValue().size();
836 return numOfUniqueTransitions;
839 // --- Functions related to cycle detection and reachability graph
841 // Detect cycles in the current execution/trace
842 // We terminate the execution iff:
843 // (1) the state has been visited in the current execution
844 // (2) the state has one or more cycles that involve all the events
845 // With simple approach we only need to check for a re-visited state.
846 // Basically, we have to check that we have executed all events between two occurrences of such state.
847 private boolean completeFullCycle(int stId) {
848 // False if the state ID hasn't been recorded
849 if (!stateToEventMap.containsKey(stId)) {
852 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
853 // Check if this set contains all the event choices
854 // If not then this is not the terminating condition
855 for(int i=0; i<=maxEventChoice; i++) {
856 if (!visitedEvents.contains(i)) {
863 private void initializeStatesVariables() {
870 if (!isBooleanCGFlipped) {
871 currVisitedStates = new HashMap<>();
872 justVisitedStates = new HashSet<>();
873 prevVisitedStates = new HashSet<>();
874 stateToEventMap = new HashMap<>();
876 currVisitedStates.clear();
877 justVisitedStates.clear();
878 prevVisitedStates.clear();
879 stateToEventMap.clear();
882 if (!isBooleanCGFlipped) {
883 backtrackMap = new HashMap<>();
885 backtrackMap.clear();
887 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
888 currentExecution = new Execution();
889 currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
890 if (!isBooleanCGFlipped) {
891 doneBacktrackMap = new HashMap<>();
893 doneBacktrackMap.clear();
895 rGraph = new RGraph();
897 isEndOfExecution = false;
900 private void mapStateToEvent(int nextChoiceValue) {
901 // Update all states with this event/choice
902 // This means that all past states now see this transition
903 Set<Integer> stateSet = stateToEventMap.keySet();
904 for(Integer stateId : stateSet) {
905 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
906 eventSet.add(nextChoiceValue);
910 private boolean terminateCurrentExecution() {
911 // We need to check all the states that have just been visited
912 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
913 boolean terminate = false;
914 Set<Integer> mainStateIds = mainSummary.getStateIds();
915 for(Integer stateId : justVisitedStates) {
916 // We exclude states that are produced by other CGs that are not integer CG
917 // When we encounter these states, then we should also encounter the corresponding integer CG state ID
918 if (mainStateIds.contains(stateId)) {
919 // We perform updates on backtrack sets for every
920 if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
921 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
924 // If frequency > 1 then this means we have visited this stateId more than once in the current execution
925 if (currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) {
926 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
933 private void updateStateInfo(Search search) {
934 // Update the state variables
935 int stateId = search.getStateId();
936 // Insert state ID into the map if it is new
937 if (!stateToEventMap.containsKey(stateId)) {
938 HashSet<Integer> eventSet = new HashSet<>();
939 stateToEventMap.put(stateId, eventSet);
941 addPredecessorToRevisitedState(stateId);
942 justVisitedStates.add(stateId);
943 if (!prevVisitedStates.contains(stateId)) {
944 // It is a currently visited states if the state has not been seen in previous executions
946 if (currVisitedStates.containsKey(stateId)) {
947 frequency = currVisitedStates.get(stateId);
949 currVisitedStates.put(stateId, frequency + 1); // Increment frequency counter
953 // --- Functions related to Read/Write access analysis on shared fields
955 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList, TransitionEvent conflictTransition) {
956 // Insert backtrack point to the right state ID
957 LinkedList<BacktrackExecution> backtrackExecList;
958 if (backtrackMap.containsKey(stateId)) {
959 backtrackExecList = backtrackMap.get(stateId);
961 backtrackExecList = new LinkedList<>();
962 backtrackMap.put(stateId, backtrackExecList);
964 // Add the new backtrack execution object
965 TransitionEvent backtrackTransition = new TransitionEvent();
966 backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
967 // Add to priority queue
968 if (!backtrackStateQ.contains(stateId)) {
969 backtrackStateQ.add(stateId);
973 private void addPredecessors(int stateId) {
974 PredecessorInfo predecessorInfo;
975 if (!stateToPredInfo.containsKey(stateId)) {
976 predecessorInfo = new PredecessorInfo();
977 stateToPredInfo.put(stateId, predecessorInfo);
978 } else { // This is a new state Id
979 predecessorInfo = stateToPredInfo.get(stateId);
981 predecessorInfo.recordPredecessor(currentExecution, choiceCounter - 1);
984 // Analyze Read/Write accesses that are directly invoked on fields
985 private void analyzeReadWriteAccesses(Instruction executedInsn, int currentChoice) {
986 // Get the field info
987 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
988 // Analyze only after being initialized
989 String fieldClass = fieldInfo.getFullName();
990 // Do the analysis to get Read and Write accesses to fields
991 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
992 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
993 // Record the field in the map
994 if (executedInsn instanceof WriteInstruction) {
995 // We first check the non-relevant fields set
996 if (!nonRelevantFields.contains(fieldInfo)) {
997 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
998 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
999 if (fieldClass.startsWith(str)) {
1000 nonRelevantFields.add(fieldInfo);
1005 // If we have this field in the non-relevant fields set then we return right away
1008 rwSet.addWriteField(fieldClass, objectId);
1009 } else if (executedInsn instanceof ReadInstruction) {
1010 rwSet.addReadField(fieldClass, objectId);
1014 // Analyze Read accesses that are indirect (performed through iterators)
1015 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
1016 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
1018 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
1019 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
1020 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
1021 // Extract info from the stack frame
1022 StackFrame frame = ti.getTopFrame();
1023 int[] frameSlots = frame.getSlots();
1024 // Get the Groovy callsite library at index 0
1025 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
1026 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
1029 // Get the iterated object whose property is accessed
1030 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
1031 if (eiAccessObj == null) {
1034 // We exclude library classes (they start with java, org, etc.) and some more
1035 ClassInfo classInfo = eiAccessObj.getClassInfo();
1036 String objClassName = classInfo.getName();
1037 // Check if this class info is part of the non-relevant classes set already
1038 if (!nonRelevantClasses.contains(classInfo)) {
1039 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName) ||
1040 excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName)) {
1041 nonRelevantClasses.add(classInfo);
1045 // If it is part of the non-relevant classes set then return immediately
1048 // Extract fields from this object and put them into the read write
1049 int numOfFields = eiAccessObj.getNumberOfFields();
1050 for(int i=0; i<numOfFields; i++) {
1051 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
1052 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
1053 String fieldClass = fieldInfo.getFullName();
1054 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
1055 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
1056 // Record the field in the map
1057 rwSet.addReadField(fieldClass, objectId);
1063 private int checkAndAdjustChoice(int currentChoice, VM vm) {
1064 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
1065 // for certain method calls in the infrastructure, e.g., eventSince()
1066 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
1067 // This is the main event CG
1068 if (currentCG instanceof IntIntervalGenerator) {
1069 // This is the interval CG used in device handlers
1070 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
1071 // Iterate until we find the IntChoiceFromSet CG
1072 while (!(parentCG instanceof IntChoiceFromSet)) {
1073 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
1075 // Find the choice related to the IntIntervalGenerator CG from the map
1076 currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
1078 return currentChoice;
1081 private void createBacktrackingPoint(int eventChoice, Execution conflictExecution, int conflictChoice) {
1082 // Create a new list of choices for backtrack based on the current choice and conflicting event number
1083 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
1084 // for the original set {0, 1, 2, 3}
1086 // eventChoice represents the event/transaction that will be put into the backtracking set of
1087 // conflictExecution/conflictChoice
1088 Integer[] newChoiceList = new Integer[refChoices.length];
1089 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1090 int stateId = conflictTrace.get(conflictChoice).getStateId();
1091 // Check if this trace has been done from this state
1092 if (isTraceAlreadyConstructed(eventChoice, stateId)) {
1095 // Put the conflicting event numbers first and reverse the order
1096 newChoiceList[0] = eventChoice;
1097 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
1098 for (int i = 0, j = 1; i < refChoices.length; i++) {
1099 if (refChoices[i] != newChoiceList[0]) {
1100 newChoiceList[j] = refChoices[i];
1104 // Predecessor of the new backtrack point is the same as the conflict point's
1105 addNewBacktrackPoint(stateId, newChoiceList, conflictTrace.get(conflictChoice));
1108 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
1109 for (String excludedField : excludedStrings) {
1110 if (className.contains(excludedField)) {
1117 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
1118 for (String excludedField : excludedStrings) {
1119 if (className.endsWith(excludedField)) {
1126 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
1127 for (String excludedField : excludedStrings) {
1128 if (className.startsWith(excludedField)) {
1135 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
1136 // Check if we are reaching the end of our execution: no more backtracking points to explore
1137 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
1138 if (!backtrackStateQ.isEmpty()) {
1139 // Set done all the other backtrack points
1140 for (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
1141 backtrackTransition.getTransitionCG().setDone();
1143 // Reset the next backtrack point with the latest state
1144 int hiStateId = backtrackStateQ.peek();
1145 // Restore the state first if necessary
1146 if (vm.getStateId() != hiStateId) {
1147 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
1148 vm.restoreState(restorableState);
1150 // Set the backtrack CG
1151 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
1152 setBacktrackCG(hiStateId, backtrackCG);
1154 // Set done this last CG (we save a few rounds)
1157 // Save all the visited states when starting a new execution of trace
1158 prevVisitedStates.addAll(currVisitedStates.keySet());
1159 // This marks a transitional period to the new CG
1160 isEndOfExecution = true;
1163 private boolean isConflictFound(int eventChoice, Execution conflictExecution, int conflictChoice,
1164 ReadWriteSet currRWSet) {
1165 // conflictExecution/conflictChoice represent a predecessor event/transaction that can potentially have a conflict
1166 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1167 HashMap<Integer, ReadWriteSet> confRWFieldsMap = conflictExecution.getReadWriteFieldsMap();
1168 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
1169 if (!confRWFieldsMap.containsKey(conflictChoice) || eventChoice == conflictTrace.get(conflictChoice).getChoice()) {
1172 // R/W set of choice/event that may have a potential conflict
1173 ReadWriteSet confRWSet = confRWFieldsMap.get(conflictChoice);
1174 // Check for conflicts with Read and Write fields for Write instructions
1175 Set<String> currWriteSet = currRWSet.getWriteSet();
1176 for(String writeField : currWriteSet) {
1177 int currObjId = currRWSet.writeFieldObjectId(writeField);
1178 if ((confRWSet.readFieldExists(writeField) && confRWSet.readFieldObjectId(writeField) == currObjId) ||
1179 (confRWSet.writeFieldExists(writeField) && confRWSet.writeFieldObjectId(writeField) == currObjId)) {
1180 // Remove this from the write set as we are tracking per memory location
1181 currRWSet.removeWriteField(writeField);
1185 // Check for conflicts with Write fields for Read instructions
1186 Set<String> currReadSet = currRWSet.getReadSet();
1187 for(String readField : currReadSet) {
1188 int currObjId = currRWSet.readFieldObjectId(readField);
1189 if (confRWSet.writeFieldExists(readField) && confRWSet.writeFieldObjectId(readField) == currObjId) {
1190 // Remove this from the read set as we are tracking per memory location
1191 currRWSet.removeReadField(readField);
1195 // Return false if no conflict is found
1199 private boolean isFieldExcluded(Instruction executedInsn) {
1200 // Get the field info
1201 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
1202 // Check if the non-relevant fields set already has it
1203 if (nonRelevantFields.contains(fieldInfo)) {
1206 // Check if the relevant fields set already has it
1207 if (relevantFields.contains(fieldInfo)) {
1210 // Analyze only after being initialized
1211 String field = fieldInfo.getFullName();
1212 // Check against "starts-with", "ends-with", and "contains" list
1213 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
1214 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
1215 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
1216 nonRelevantFields.add(fieldInfo);
1219 relevantFields.add(fieldInfo);
1223 // Check if this trace is already constructed
1224 private boolean isTraceAlreadyConstructed(int firstChoice, int stateId) {
1225 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
1226 // Check if the trace has been constructed as a backtrack point for this state
1227 // TODO: THIS IS AN OPTIMIZATION!
1228 HashSet<Integer> choiceSet;
1229 if (doneBacktrackMap.containsKey(stateId)) {
1230 choiceSet = doneBacktrackMap.get(stateId);
1231 if (choiceSet.contains(firstChoice)) {
1235 choiceSet = new HashSet<>();
1236 doneBacktrackMap.put(stateId, choiceSet);
1238 choiceSet.add(firstChoice);
1243 private HashSet<Predecessor> getPredecessors(int stateId) {
1244 // Get a set of predecessors for this state ID
1245 HashSet<Predecessor> predecessors;
1246 if (stateToPredInfo.containsKey(stateId)) {
1247 PredecessorInfo predecessorInfo = stateToPredInfo.get(stateId);
1248 predecessors = predecessorInfo.getPredecessors();
1250 predecessors = new HashSet<>();
1253 return predecessors;
1256 private ReadWriteSet getReadWriteSet(int currentChoice) {
1257 // Do the analysis to get Read and Write accesses to fields
1259 // We already have an entry
1260 HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
1261 if (currReadWriteFieldsMap.containsKey(currentChoice)) {
1262 rwSet = currReadWriteFieldsMap.get(currentChoice);
1263 } else { // We need to create a new entry
1264 rwSet = new ReadWriteSet();
1265 currReadWriteFieldsMap.put(currentChoice, rwSet);
1270 // Reset data structure for each new execution
1271 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
1272 if (choices == null || choices != icsCG.getAllChoices()) {
1273 // Reset state variables
1275 choices = icsCG.getAllChoices();
1276 refChoices = copyChoices(choices);
1277 // Clear data structures
1278 currVisitedStates.clear();
1279 stateToEventMap.clear();
1280 isEndOfExecution = false;
1284 // Set a backtrack point for a particular state
1285 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
1286 // Set a backtrack CG based on a state ID
1287 LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
1288 BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
1289 backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
1290 backtrackCG.setStateId(stateId);
1291 backtrackCG.reset();
1292 // Update current execution with this new execution
1293 Execution newExecution = new Execution();
1294 TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
1295 newExecution.addTransition(firstTransition);
1296 // Try to free some memory since this map is only used for the current execution
1297 currentExecution.clearCGToChoiceMap();
1298 currentExecution = newExecution;
1299 // Remove from the queue if we don't have more backtrack points for that state
1300 if (backtrackExecutions.isEmpty()) {
1301 backtrackMap.remove(stateId);
1302 backtrackStateQ.remove(stateId);
1306 // Update backtrack sets
1307 // 1) recursively, and
1308 // 2) track accesses per memory location (per shared variable/field)
1309 private void updateBacktrackSet(Execution execution, int currentChoice) {
1310 // Copy ReadWriteSet object
1311 HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
1312 ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice);
1313 if (currRWSet == null) {
1316 currRWSet = currRWSet.getCopy();
1317 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1318 HashSet<TransitionEvent> visited = new HashSet<>();
1319 // Conflict TransitionEvent is essentially the current TransitionEvent
1320 TransitionEvent confTrans = execution.getExecutionTrace().get(currentChoice);
1321 // Update backtrack set recursively
1322 updateBacktrackSetDFS(execution, currentChoice, confTrans.getChoice(), currRWSet, visited);
1325 private void updateBacktrackSetDFS(Execution execution, int currentChoice, int conflictEventChoice,
1326 ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
1327 TransitionEvent currTrans = execution.getExecutionTrace().get(currentChoice);
1328 // Record this transition into the state summary of main summary
1329 currRWSet = mainSummary.updateStateSummary(currTrans.getStateId(), conflictEventChoice, currRWSet);
1330 // Halt when we have visited this transition (in a cycle)
1331 if (visited.contains(currTrans)) {
1334 visited.add(currTrans);
1335 // Check the predecessors only if the set is not empty
1336 if (!currRWSet.isEmpty()) {
1337 // Explore all predecessors
1338 for (Predecessor predecessor : getPredecessors(currTrans.getStateId())) {
1339 // Get the predecessor (previous conflict choice)
1340 int predecessorChoice = predecessor.getChoice();
1341 Execution predecessorExecution = predecessor.getExecution();
1342 // Push up one happens-before transition
1343 int newConflictEventChoice = conflictEventChoice;
1344 // Check if a conflict is found
1345 ReadWriteSet newCurrRWSet = currRWSet.getCopy();
1346 if (isConflictFound(conflictEventChoice, predecessorExecution, predecessorChoice, newCurrRWSet)) {
1347 createBacktrackingPoint(conflictEventChoice, predecessorExecution, predecessorChoice);
1348 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1349 newConflictEventChoice = predecessorExecution.getExecutionTrace().get(predecessorChoice).getChoice();
1351 // Continue performing DFS if conflict is not found
1352 updateBacktrackSetDFS(predecessorExecution, predecessorChoice, newConflictEventChoice,
1353 newCurrRWSet, visited);
1358 // --- Functions related to the reachability analysis when there is a state match
1360 private void addPredecessorToRevisitedState(int stateId) {
1361 // Perform this analysis only when:
1362 // 1) this is not during a switch to a new execution,
1363 // 2) at least 2 choices/events have been explored (choiceCounter > 1),
1364 // 3) state > 0 (state 0 is for boolean CG)
1365 if (!isEndOfExecution && choiceCounter > 1 && stateId > 0) {
1366 if ((currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) ||
1367 prevVisitedStates.contains(stateId)) {
1368 // Record a new predecessor for a revisited state
1369 addPredecessors(stateId);
1374 // Update the backtrack sets from previous executions
1375 private void updateBacktrackSetsFromGraph(int stateId, Execution currExecution, int currChoice) {
1376 // Get events/choices at this state ID
1377 Set<Integer> eventChoicesAtStateId = mainSummary.getEventChoicesAtStateId(stateId);
1378 for (Integer eventChoice : eventChoicesAtStateId) {
1379 // Get the ReadWriteSet object for this event at state ID
1380 ReadWriteSet rwSet = mainSummary.getRWSetForEventChoiceAtState(eventChoice, stateId).getCopy();
1381 // We have to first check for conflicts between the event and the current transition
1382 // Push up one happens-before transition
1383 int conflictEventChoice = eventChoice;
1384 if (isConflictFound(eventChoice, currExecution, currChoice, rwSet)) {
1385 createBacktrackingPoint(eventChoice, currExecution, currChoice);
1386 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1387 conflictEventChoice = currExecution.getExecutionTrace().get(currChoice).getChoice();
1389 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1390 HashSet<TransitionEvent> visited = new HashSet<>();
1391 // Update the backtrack sets recursively
1392 updateBacktrackSetDFS(currExecution, currChoice, conflictEventChoice, rwSet, visited);