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>> stateToUniqueEventMap;
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 stateToUniqueEventMap = 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 out.println("\n==> DEBUG: ----------------------------------- search finished");
183 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
184 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
185 out.println("\n==> DEBUG: Number of unique transitions (DPOR) : " + summarizeUniqueStateIds());
186 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
188 fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
189 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
190 fileWriter.println("==> DEBUG: Number of unique transitions : " + summarizeUniqueStateIds());
191 fileWriter.println();
197 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
198 if (isNotCheckedForEventsYet) {
199 // Check if this benchmark has no events
200 if (nextCG instanceof IntChoiceFromSet) {
201 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
202 Integer[] cgChoices = icsCG.getAllChoices();
203 if (cgChoices.length == 2 && cgChoices[0] == 0 && cgChoices[1] == -1) {
204 // This means the benchmark only has 2 choices, i.e., 0 and -1 which means that it has no events
205 stateReductionMode = false;
207 isNotCheckedForEventsYet = false;
210 if (stateReductionMode) {
211 // Initialize with necessary information from the CG
212 if (nextCG instanceof IntChoiceFromSet) {
213 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
214 // Tell JPF that we are performing DPOR
216 if (!isEndOfExecution) {
217 // Check if CG has been initialized, otherwise initialize it
218 Integer[] cgChoices = icsCG.getAllChoices();
219 // Record the events (from choices)
220 if (choices == null) {
222 // Make a copy of choices as reference
223 refChoices = copyChoices(choices);
224 // Record the max event choice (the last element of the choice array)
225 maxEventChoice = choices[choices.length - 1];
227 icsCG.setNewValues(choices);
229 // Use a modulo since choiceCounter is going to keep increasing
230 int choiceIndex = choiceCounter % choices.length;
231 icsCG.advance(choices[choiceIndex]);
233 // Set done all CGs while transitioning to a new execution
241 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
242 if (stateReductionMode) {
243 // Check the boolean CG and if it is flipped, we are resetting the analysis
244 if (currentCG instanceof BooleanChoiceGenerator) {
245 if (!isBooleanCGFlipped) {
246 isBooleanCGFlipped = true;
248 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
249 initializeStatesVariables();
252 // Check every choice generated and ensure fair scheduling!
253 if (currentCG instanceof IntChoiceFromSet) {
254 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
255 // If this is a new CG then we need to update data structures
256 resetStatesForNewExecution(icsCG, vm);
257 // If we don't see a fair scheduling of events/choices then we have to enforce it
258 ensureFairSchedulingAndSetupTransition(icsCG, vm);
259 // Update backtrack set of an executed event (transition): one transition before this one
260 updateBacktrackSet(currentExecution, choiceCounter - 1);
261 // Explore the next backtrack point:
262 // 1) if we have seen this state or this state contains cycles that involve all events, and
263 // 2) after the current CG is advanced at least once
264 if (choiceCounter > 0 && terminateCurrentExecution()) {
265 exploreNextBacktrackPoints(vm, icsCG);
268 countUniqueStateId(vm.getStateId(), icsCG.getNextChoice());
270 // Map state to event
271 mapStateToEvent(icsCG.getNextChoice());
272 justVisitedStates.clear();
280 // Count unique state IDs
281 private void countUniqueStateId(int stateId, int nextChoiceValue) {
282 HashSet<Integer> events;
283 // Get the set of events
284 if (!stateToUniqueEventMap.containsKey(stateId)) {
285 events = new HashSet<>();
286 stateToUniqueEventMap.put(stateId, events);
288 events = stateToUniqueEventMap.get(stateId);
291 if (!events.contains(nextChoiceValue)) {
292 events.add(nextChoiceValue);
296 // Summarize unique state IDs
297 private int summarizeUniqueStateIds() {
298 // Just count the set size of each of entry map and sum them up
299 int numOfUniqueTransitions = 0;
300 for (Map.Entry<Integer,HashSet<Integer>> entry : stateToUniqueEventMap.entrySet()) {
301 numOfUniqueTransitions = numOfUniqueTransitions + entry.getValue().size();
303 // We also need to count root and boolean CG if this is in state reduction mode (DPOR)
304 if (stateReductionMode) {
305 numOfUniqueTransitions = numOfUniqueTransitions + 3;
308 return numOfUniqueTransitions;
312 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
313 if (stateReductionMode) {
314 if (!isEndOfExecution) {
315 // Has to be initialized and it is a integer CG
316 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
317 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
318 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
319 if (currentChoice < 0) { // If choice is -1 then skip
322 currentChoice = checkAndAdjustChoice(currentChoice, vm);
323 // Record accesses from executed instructions
324 if (executedInsn instanceof JVMFieldInstruction) {
325 // We don't care about libraries
326 if (!isFieldExcluded(executedInsn)) {
327 analyzeReadWriteAccesses(executedInsn, currentChoice);
329 } else if (executedInsn instanceof INVOKEINTERFACE) {
330 // Handle the read/write accesses that occur through iterators
331 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
343 // This class compactly stores backtrack execution:
344 // 1) backtrack choice list, and
345 // 2) first backtrack point (linking with predecessor execution)
346 private class BacktrackExecution {
347 private Integer[] choiceList;
348 private TransitionEvent firstTransition;
350 public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
351 choiceList = choList;
352 firstTransition = fTransition;
355 public Integer[] getChoiceList() {
359 public TransitionEvent getFirstTransition() {
360 return firstTransition;
364 // This class stores a representation of an execution
365 // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
366 // TODO: We basically need to keep track of:
367 // TODO: (1) last read/write access to each memory location
368 // TODO: (2) last state with two or more incoming events/transitions
369 private class Execution {
370 private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
371 private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
372 private boolean isNew; // Track if this is the first time it is accessed
373 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
376 cgToChoiceMap = new HashMap<>();
377 executionTrace = new ArrayList<>();
379 readWriteFieldsMap = new HashMap<>();
382 public void addTransition(TransitionEvent newBacktrackPoint) {
383 executionTrace.add(newBacktrackPoint);
386 public void clearCGToChoiceMap() {
387 cgToChoiceMap = null;
390 public int getChoiceFromCG(IntChoiceFromSet icsCG) {
391 return cgToChoiceMap.get(icsCG);
394 public ArrayList<TransitionEvent> getExecutionTrace() {
395 return executionTrace;
398 public TransitionEvent getFirstTransition() {
399 return executionTrace.get(0);
402 public TransitionEvent getLastTransition() {
403 return executionTrace.get(executionTrace.size() - 1);
406 public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
407 return readWriteFieldsMap;
410 public boolean isNew() {
412 // Right after this is accessed, it is no longer new
419 public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
420 cgToChoiceMap.put(icsCG, choice);
424 // This class compactly stores a predecessor
425 // 1) a predecessor execution
426 // 2) the predecessor choice in that predecessor execution
427 private class Predecessor {
428 private int choice; // Predecessor choice
429 private Execution execution; // Predecessor execution
431 public Predecessor(int predChoice, Execution predExec) {
433 execution = predExec;
436 public int getChoice() {
440 public Execution getExecution() {
445 // This class represents a R-Graph (in the paper it is a state transition graph R)
446 // This implementation stores reachable transitions from and connects with past executions
447 private class RGraph {
448 private int hiStateId; // Maximum state Id
449 private HashMap<Integer, HashSet<TransitionEvent>> graph; // Reachable transitions from past executions
453 graph = new HashMap<>();
456 public void addReachableTransition(int stateId, TransitionEvent transition) {
457 HashSet<TransitionEvent> transitionSet;
458 if (graph.containsKey(stateId)) {
459 transitionSet = graph.get(stateId);
461 transitionSet = new HashSet<>();
462 graph.put(stateId, transitionSet);
464 // Insert into the set if it does not contain it yet
465 if (!transitionSet.contains(transition)) {
466 transitionSet.add(transition);
468 // Update highest state ID
469 if (hiStateId < stateId) {
474 public HashSet<TransitionEvent> getReachableTransitionsAtState(int stateId) {
475 if (!graph.containsKey(stateId)) {
476 // This is a loop from a transition to itself, so just return the current transition
477 HashSet<TransitionEvent> transitionSet = new HashSet<>();
478 transitionSet.add(currentExecution.getLastTransition());
479 return transitionSet;
481 return graph.get(stateId);
484 public HashSet<TransitionEvent> getReachableTransitions(int stateId) {
485 HashSet<TransitionEvent> reachableTransitions = new HashSet<>();
486 // All transitions from states higher than the given state ID (until the highest state ID) are reachable
487 for(int stId = stateId; stId <= hiStateId; stId++) {
488 // We might encounter state IDs from the first round of Boolean CG
489 // The second round of Boolean CG should consider these new states
490 if (graph.containsKey(stId)) {
491 reachableTransitions.addAll(graph.get(stId));
494 return reachableTransitions;
498 // This class compactly stores Read and Write field sets
499 // We store the field name and its object ID
500 // Sharing the same field means the same field name and object ID
501 private class ReadWriteSet {
502 private HashMap<String, Integer> readMap;
503 private HashMap<String, Integer> writeMap;
505 public ReadWriteSet() {
506 readMap = new HashMap<>();
507 writeMap = new HashMap<>();
510 public void addReadField(String field, int objectId) {
511 readMap.put(field, objectId);
514 public void addWriteField(String field, int objectId) {
515 writeMap.put(field, objectId);
518 public void removeReadField(String field) {
519 readMap.remove(field);
522 public void removeWriteField(String field) {
523 writeMap.remove(field);
526 public boolean isEmpty() {
527 return readMap.isEmpty() && writeMap.isEmpty();
530 public ReadWriteSet getCopy() {
531 ReadWriteSet copyRWSet = new ReadWriteSet();
532 // Copy the maps in the set into the new object copy
533 copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
534 copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
538 public Set<String> getReadSet() {
539 return readMap.keySet();
542 public Set<String> getWriteSet() {
543 return writeMap.keySet();
546 public boolean readFieldExists(String field) {
547 return readMap.containsKey(field);
550 public boolean writeFieldExists(String field) {
551 return writeMap.containsKey(field);
554 public int readFieldObjectId(String field) {
555 return readMap.get(field);
558 public int writeFieldObjectId(String field) {
559 return writeMap.get(field);
562 private HashMap<String, Integer> getReadMap() {
566 private HashMap<String, Integer> getWriteMap() {
570 private void setReadMap(HashMap<String, Integer> rMap) {
574 private void setWriteMap(HashMap<String, Integer> wMap) {
579 // This class is a representation of a state.
580 // It stores the predecessors to a state.
581 // TODO: We also have stateToEventMap, restorableStateMap, and doneBacktrackMap that has state Id as HashMap key.
582 private class PredecessorInfo {
583 private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
584 private HashMap<Execution, HashSet<Integer>> recordedPredecessors;
585 // Memorize event and choice number to not record them twice
587 public PredecessorInfo() {
588 predecessors = new HashSet<>();
589 recordedPredecessors = new HashMap<>();
592 public HashSet<Predecessor> getPredecessors() {
596 private boolean isRecordedPredecessor(Execution execution, int choice) {
597 // See if we have recorded this predecessor earlier
598 HashSet<Integer> recordedChoices;
599 if (recordedPredecessors.containsKey(execution)) {
600 recordedChoices = recordedPredecessors.get(execution);
601 if (recordedChoices.contains(choice)) {
605 recordedChoices = new HashSet<>();
606 recordedPredecessors.put(execution, recordedChoices);
608 // Record the choice if we haven't seen it
609 recordedChoices.add(choice);
614 public void recordPredecessor(Execution execution, int choice) {
615 if (!isRecordedPredecessor(execution, choice)) {
616 predecessors.add(new Predecessor(choice, execution));
621 // This class compactly stores transitions:
625 // 4) predecessors (for backward DFS).
626 private class TransitionEvent {
627 private int choice; // Choice chosen at this transition
628 private int choiceCounter; // Choice counter at this transition
629 private Execution execution; // The execution where this transition belongs
630 private int stateId; // State at this transition
631 private IntChoiceFromSet transitionCG; // CG at this transition
633 public TransitionEvent() {
641 public int getChoice() {
645 public int getChoiceCounter() {
646 return choiceCounter;
649 public Execution getExecution() {
653 public int getStateId() {
657 public IntChoiceFromSet getTransitionCG() { return transitionCG; }
659 public void setChoice(int cho) {
663 public void setChoiceCounter(int choCounter) {
664 choiceCounter = choCounter;
667 public void setExecution(Execution exec) {
671 public void setStateId(int stId) {
675 public void setTransitionCG(IntChoiceFromSet cg) {
680 // -- PRIVATE CLASSES RELATED TO SUMMARY
681 // This class stores the main summary of states
682 // 1) Main mapping between state ID and state summary
683 // 2) State summary is a mapping between events (i.e., event choices) and their respective R/W sets
684 private class MainSummary {
685 private HashMap<Integer, HashMap<Integer, ReadWriteSet>> mainSummary;
687 public MainSummary() {
688 mainSummary = new HashMap<>();
691 public Set<Integer> getEventChoicesAtStateId(int stateId) {
692 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
693 // Return a new set since this might get updated concurrently
694 return new HashSet<>(stateSummary.keySet());
697 public ReadWriteSet getRWSetForEventChoiceAtState(int eventChoice, int stateId) {
698 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
699 return stateSummary.get(eventChoice);
702 public Set<Integer> getStateIds() {
703 return mainSummary.keySet();
706 private ReadWriteSet performUnion(ReadWriteSet recordedRWSet, ReadWriteSet rwSet) {
707 // Combine the same write accesses and record in the recordedRWSet
708 HashMap<String, Integer> recordedWriteMap = recordedRWSet.getWriteMap();
709 HashMap<String, Integer> writeMap = rwSet.getWriteMap();
710 for(Map.Entry<String, Integer> entry : recordedWriteMap.entrySet()) {
711 String writeField = entry.getKey();
712 // Remove the entry from rwSet if both field and object ID are the same
713 if (writeMap.containsKey(writeField) &&
714 (writeMap.get(writeField).equals(recordedWriteMap.get(writeField)))) {
715 writeMap.remove(writeField);
718 // Then add the rest (fields in rwSet but not in recordedRWSet)
719 // into the recorded map because these will be traversed
720 recordedWriteMap.putAll(writeMap);
721 // Combine the same read accesses and record in the recordedRWSet
722 HashMap<String, Integer> recordedReadMap = recordedRWSet.getReadMap();
723 HashMap<String, Integer> readMap = rwSet.getReadMap();
724 for(Map.Entry<String, Integer> entry : recordedReadMap.entrySet()) {
725 String readField = entry.getKey();
726 // Remove the entry from rwSet if both field and object ID are the same
727 if (readMap.containsKey(readField) &&
728 (readMap.get(readField).equals(recordedReadMap.get(readField)))) {
729 readMap.remove(readField);
732 // Then add the rest (fields in rwSet but not in recordedRWSet)
733 // into the recorded map because these will be traversed
734 recordedReadMap.putAll(readMap);
739 public ReadWriteSet updateStateSummary(int stateId, int eventChoice, ReadWriteSet rwSet) {
740 // If the state Id has not existed, insert the StateSummary object
741 // If the state Id has existed, find the event choice:
742 // 1) If the event choice has not existed, insert the ReadWriteSet object
743 // 2) If the event choice has existed, perform union between the two ReadWriteSet objects
744 if (!rwSet.isEmpty()) {
745 HashMap<Integer, ReadWriteSet> stateSummary;
746 if (!mainSummary.containsKey(stateId)) {
747 stateSummary = new HashMap<>();
748 stateSummary.put(eventChoice, rwSet.getCopy());
749 mainSummary.put(stateId, stateSummary);
751 stateSummary = mainSummary.get(stateId);
752 if (!stateSummary.containsKey(eventChoice)) {
753 stateSummary.put(eventChoice, rwSet.getCopy());
755 rwSet = performUnion(stateSummary.get(eventChoice), rwSet);
764 private final static String DO_CALL_METHOD = "doCall";
765 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
766 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
767 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
768 // Groovy library created fields
769 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
771 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
772 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
773 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
774 // Java and Groovy libraries
775 { "java", "org", "sun", "com", "gov", "groovy"};
776 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
777 private final static String GET_PROPERTY_METHOD =
778 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
779 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
780 private final static String JAVA_INTEGER = "int";
781 private final static String JAVA_STRING_LIB = "java.lang.String";
784 private Integer[] copyChoices(Integer[] choicesToCopy) {
786 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
787 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
788 return copyOfChoices;
791 private void ensureFairSchedulingAndSetupTransition(IntChoiceFromSet icsCG, VM vm) {
792 // Check the next choice and if the value is not the same as the expected then force the expected value
793 int choiceIndex = choiceCounter % refChoices.length;
794 int nextChoice = icsCG.getNextChoice();
795 if (refChoices[choiceIndex] != nextChoice) {
796 int expectedChoice = refChoices[choiceIndex];
797 int currCGIndex = icsCG.getNextChoiceIndex();
798 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
799 icsCG.setChoice(currCGIndex, expectedChoice);
802 // Get state ID and associate it with this transition
803 int stateId = vm.getStateId();
804 TransitionEvent transition = setupTransition(icsCG, stateId, choiceIndex);
805 // Add new transition to the current execution and map it in R-Graph
806 for (Integer stId : justVisitedStates) { // Map this transition to all the previously passed states
807 rGraph.addReachableTransition(stId, transition);
809 currentExecution.mapCGToChoice(icsCG, choiceCounter);
810 // Store restorable state object for this state (always store the latest)
811 if (!restorableStateMap.containsKey(stateId)) {
812 RestorableVMState restorableState = vm.getRestorableState();
813 restorableStateMap.put(stateId, restorableState);
817 private TransitionEvent setupTransition(IntChoiceFromSet icsCG, int stateId, int choiceIndex) {
818 // Get a new transition
819 TransitionEvent transition;
820 if (currentExecution.isNew()) {
821 // We need to handle the first transition differently because this has a predecessor execution
822 transition = currentExecution.getFirstTransition();
824 transition = new TransitionEvent();
825 currentExecution.addTransition(transition);
826 addPredecessors(stateId);
828 transition.setExecution(currentExecution);
829 transition.setTransitionCG(icsCG);
830 transition.setStateId(stateId);
831 transition.setChoice(refChoices[choiceIndex]);
832 transition.setChoiceCounter(choiceCounter);
837 // --- Functions related to cycle detection and reachability graph
839 // Detect cycles in the current execution/trace
840 // We terminate the execution iff:
841 // (1) the state has been visited in the current execution
842 // (2) the state has one or more cycles that involve all the events
843 // With simple approach we only need to check for a re-visited state.
844 // Basically, we have to check that we have executed all events between two occurrences of such state.
845 private boolean completeFullCycle(int stId) {
846 // False if the state ID hasn't been recorded
847 if (!stateToEventMap.containsKey(stId)) {
850 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
851 // Check if this set contains all the event choices
852 // If not then this is not the terminating condition
853 for(int i=0; i<=maxEventChoice; i++) {
854 if (!visitedEvents.contains(i)) {
861 private void initializeStatesVariables() {
868 if (!isBooleanCGFlipped) {
869 currVisitedStates = new HashMap<>();
870 justVisitedStates = new HashSet<>();
871 prevVisitedStates = new HashSet<>();
872 stateToEventMap = new HashMap<>();
874 currVisitedStates.clear();
875 justVisitedStates.clear();
876 prevVisitedStates.clear();
877 stateToEventMap.clear();
880 if (!isBooleanCGFlipped) {
881 backtrackMap = new HashMap<>();
883 backtrackMap.clear();
885 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
886 currentExecution = new Execution();
887 currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
888 if (!isBooleanCGFlipped) {
889 doneBacktrackMap = new HashMap<>();
891 doneBacktrackMap.clear();
893 rGraph = new RGraph();
895 isEndOfExecution = false;
898 private void mapStateToEvent(int nextChoiceValue) {
899 // Update all states with this event/choice
900 // This means that all past states now see this transition
901 Set<Integer> stateSet = stateToEventMap.keySet();
902 for(Integer stateId : stateSet) {
903 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
904 eventSet.add(nextChoiceValue);
908 private boolean terminateCurrentExecution() {
909 // We need to check all the states that have just been visited
910 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
911 boolean terminate = false;
912 Set<Integer> mainStateIds = mainSummary.getStateIds();
913 for(Integer stateId : justVisitedStates) {
914 // We exclude states that are produced by other CGs that are not integer CG
915 // When we encounter these states, then we should also encounter the corresponding integer CG state ID
916 if (mainStateIds.contains(stateId)) {
917 // We perform updates on backtrack sets for every
918 if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
919 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
922 // If frequency > 1 then this means we have visited this stateId more than once in the current execution
923 if (currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) {
924 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
931 private void updateStateInfo(Search search) {
932 // Update the state variables
933 int stateId = search.getStateId();
934 // Insert state ID into the map if it is new
935 if (!stateToEventMap.containsKey(stateId)) {
936 HashSet<Integer> eventSet = new HashSet<>();
937 stateToEventMap.put(stateId, eventSet);
939 addPredecessorToRevisitedState(stateId);
940 justVisitedStates.add(stateId);
941 if (!prevVisitedStates.contains(stateId)) {
942 // It is a currently visited states if the state has not been seen in previous executions
944 if (currVisitedStates.containsKey(stateId)) {
945 frequency = currVisitedStates.get(stateId);
947 currVisitedStates.put(stateId, frequency + 1); // Increment frequency counter
951 // --- Functions related to Read/Write access analysis on shared fields
953 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList, TransitionEvent conflictTransition) {
954 // Insert backtrack point to the right state ID
955 LinkedList<BacktrackExecution> backtrackExecList;
956 if (backtrackMap.containsKey(stateId)) {
957 backtrackExecList = backtrackMap.get(stateId);
959 backtrackExecList = new LinkedList<>();
960 backtrackMap.put(stateId, backtrackExecList);
962 // Add the new backtrack execution object
963 TransitionEvent backtrackTransition = new TransitionEvent();
964 backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
965 // Add to priority queue
966 if (!backtrackStateQ.contains(stateId)) {
967 backtrackStateQ.add(stateId);
971 private void addPredecessors(int stateId) {
972 PredecessorInfo predecessorInfo;
973 if (!stateToPredInfo.containsKey(stateId)) {
974 predecessorInfo = new PredecessorInfo();
975 stateToPredInfo.put(stateId, predecessorInfo);
976 } else { // This is a new state Id
977 predecessorInfo = stateToPredInfo.get(stateId);
979 predecessorInfo.recordPredecessor(currentExecution, choiceCounter - 1);
982 // Analyze Read/Write accesses that are directly invoked on fields
983 private void analyzeReadWriteAccesses(Instruction executedInsn, int currentChoice) {
984 // Get the field info
985 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
986 // Analyze only after being initialized
987 String fieldClass = fieldInfo.getFullName();
988 // Do the analysis to get Read and Write accesses to fields
989 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
990 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
991 // Record the field in the map
992 if (executedInsn instanceof WriteInstruction) {
993 // We first check the non-relevant fields set
994 if (!nonRelevantFields.contains(fieldInfo)) {
995 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
996 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
997 if (fieldClass.startsWith(str)) {
998 nonRelevantFields.add(fieldInfo);
1003 // If we have this field in the non-relevant fields set then we return right away
1006 rwSet.addWriteField(fieldClass, objectId);
1007 } else if (executedInsn instanceof ReadInstruction) {
1008 rwSet.addReadField(fieldClass, objectId);
1012 // Analyze Read accesses that are indirect (performed through iterators)
1013 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
1014 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
1016 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
1017 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
1018 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
1019 // Extract info from the stack frame
1020 StackFrame frame = ti.getTopFrame();
1021 int[] frameSlots = frame.getSlots();
1022 // Get the Groovy callsite library at index 0
1023 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
1024 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
1027 // Get the iterated object whose property is accessed
1028 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
1029 if (eiAccessObj == null) {
1032 // We exclude library classes (they start with java, org, etc.) and some more
1033 ClassInfo classInfo = eiAccessObj.getClassInfo();
1034 String objClassName = classInfo.getName();
1035 // Check if this class info is part of the non-relevant classes set already
1036 if (!nonRelevantClasses.contains(classInfo)) {
1037 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName) ||
1038 excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName)) {
1039 nonRelevantClasses.add(classInfo);
1043 // If it is part of the non-relevant classes set then return immediately
1046 // Extract fields from this object and put them into the read write
1047 int numOfFields = eiAccessObj.getNumberOfFields();
1048 for(int i=0; i<numOfFields; i++) {
1049 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
1050 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
1051 String fieldClass = fieldInfo.getFullName();
1052 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
1053 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
1054 // Record the field in the map
1055 rwSet.addReadField(fieldClass, objectId);
1061 private int checkAndAdjustChoice(int currentChoice, VM vm) {
1062 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
1063 // for certain method calls in the infrastructure, e.g., eventSince()
1064 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
1065 // This is the main event CG
1066 if (currentCG instanceof IntIntervalGenerator) {
1067 // This is the interval CG used in device handlers
1068 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
1069 // Iterate until we find the IntChoiceFromSet CG
1070 while (!(parentCG instanceof IntChoiceFromSet)) {
1071 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
1073 // Find the choice related to the IntIntervalGenerator CG from the map
1074 currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
1076 return currentChoice;
1079 private void createBacktrackingPoint(int eventChoice, Execution conflictExecution, int conflictChoice) {
1080 // Create a new list of choices for backtrack based on the current choice and conflicting event number
1081 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
1082 // for the original set {0, 1, 2, 3}
1084 // eventChoice represents the event/transaction that will be put into the backtracking set of
1085 // conflictExecution/conflictChoice
1086 Integer[] newChoiceList = new Integer[refChoices.length];
1087 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1088 int stateId = conflictTrace.get(conflictChoice).getStateId();
1089 // Check if this trace has been done from this state
1090 if (isTraceAlreadyConstructed(eventChoice, stateId)) {
1093 // Put the conflicting event numbers first and reverse the order
1094 newChoiceList[0] = eventChoice;
1095 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
1096 for (int i = 0, j = 1; i < refChoices.length; i++) {
1097 if (refChoices[i] != newChoiceList[0]) {
1098 newChoiceList[j] = refChoices[i];
1102 // Predecessor of the new backtrack point is the same as the conflict point's
1103 addNewBacktrackPoint(stateId, newChoiceList, conflictTrace.get(conflictChoice));
1106 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
1107 for (String excludedField : excludedStrings) {
1108 if (className.contains(excludedField)) {
1115 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
1116 for (String excludedField : excludedStrings) {
1117 if (className.endsWith(excludedField)) {
1124 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
1125 for (String excludedField : excludedStrings) {
1126 if (className.startsWith(excludedField)) {
1133 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
1134 // Check if we are reaching the end of our execution: no more backtracking points to explore
1135 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
1136 if (!backtrackStateQ.isEmpty()) {
1137 // Set done all the other backtrack points
1138 for (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
1139 backtrackTransition.getTransitionCG().setDone();
1141 // Reset the next backtrack point with the latest state
1142 int hiStateId = backtrackStateQ.peek();
1143 // Restore the state first if necessary
1144 if (vm.getStateId() != hiStateId) {
1145 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
1146 vm.restoreState(restorableState);
1148 // Set the backtrack CG
1149 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
1150 setBacktrackCG(hiStateId, backtrackCG);
1152 // Set done this last CG (we save a few rounds)
1155 // Save all the visited states when starting a new execution of trace
1156 prevVisitedStates.addAll(currVisitedStates.keySet());
1157 // This marks a transitional period to the new CG
1158 isEndOfExecution = true;
1161 private boolean isConflictFound(int eventChoice, Execution conflictExecution, int conflictChoice,
1162 ReadWriteSet currRWSet) {
1163 // conflictExecution/conflictChoice represent a predecessor event/transaction that can potentially have a conflict
1164 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1165 HashMap<Integer, ReadWriteSet> confRWFieldsMap = conflictExecution.getReadWriteFieldsMap();
1166 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
1167 if (!confRWFieldsMap.containsKey(conflictChoice) || eventChoice == conflictTrace.get(conflictChoice).getChoice()) {
1170 // R/W set of choice/event that may have a potential conflict
1171 ReadWriteSet confRWSet = confRWFieldsMap.get(conflictChoice);
1172 // Check for conflicts with Read and Write fields for Write instructions
1173 Set<String> currWriteSet = currRWSet.getWriteSet();
1174 for(String writeField : currWriteSet) {
1175 int currObjId = currRWSet.writeFieldObjectId(writeField);
1176 if ((confRWSet.readFieldExists(writeField) && confRWSet.readFieldObjectId(writeField) == currObjId) ||
1177 (confRWSet.writeFieldExists(writeField) && confRWSet.writeFieldObjectId(writeField) == currObjId)) {
1178 // Remove this from the write set as we are tracking per memory location
1179 currRWSet.removeWriteField(writeField);
1183 // Check for conflicts with Write fields for Read instructions
1184 Set<String> currReadSet = currRWSet.getReadSet();
1185 for(String readField : currReadSet) {
1186 int currObjId = currRWSet.readFieldObjectId(readField);
1187 if (confRWSet.writeFieldExists(readField) && confRWSet.writeFieldObjectId(readField) == currObjId) {
1188 // Remove this from the read set as we are tracking per memory location
1189 currRWSet.removeReadField(readField);
1193 // Return false if no conflict is found
1197 private boolean isFieldExcluded(Instruction executedInsn) {
1198 // Get the field info
1199 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
1200 // Check if the non-relevant fields set already has it
1201 if (nonRelevantFields.contains(fieldInfo)) {
1204 // Check if the relevant fields set already has it
1205 if (relevantFields.contains(fieldInfo)) {
1208 // Analyze only after being initialized
1209 String field = fieldInfo.getFullName();
1210 // Check against "starts-with", "ends-with", and "contains" list
1211 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
1212 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
1213 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
1214 nonRelevantFields.add(fieldInfo);
1217 relevantFields.add(fieldInfo);
1221 // Check if this trace is already constructed
1222 private boolean isTraceAlreadyConstructed(int firstChoice, int stateId) {
1223 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
1224 // Check if the trace has been constructed as a backtrack point for this state
1225 // TODO: THIS IS AN OPTIMIZATION!
1226 HashSet<Integer> choiceSet;
1227 if (doneBacktrackMap.containsKey(stateId)) {
1228 choiceSet = doneBacktrackMap.get(stateId);
1229 if (choiceSet.contains(firstChoice)) {
1233 choiceSet = new HashSet<>();
1234 doneBacktrackMap.put(stateId, choiceSet);
1236 choiceSet.add(firstChoice);
1241 private HashSet<Predecessor> getPredecessors(int stateId) {
1242 // Get a set of predecessors for this state ID
1243 HashSet<Predecessor> predecessors;
1244 if (stateToPredInfo.containsKey(stateId)) {
1245 PredecessorInfo predecessorInfo = stateToPredInfo.get(stateId);
1246 predecessors = predecessorInfo.getPredecessors();
1248 predecessors = new HashSet<>();
1251 return predecessors;
1254 private ReadWriteSet getReadWriteSet(int currentChoice) {
1255 // Do the analysis to get Read and Write accesses to fields
1257 // We already have an entry
1258 HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
1259 if (currReadWriteFieldsMap.containsKey(currentChoice)) {
1260 rwSet = currReadWriteFieldsMap.get(currentChoice);
1261 } else { // We need to create a new entry
1262 rwSet = new ReadWriteSet();
1263 currReadWriteFieldsMap.put(currentChoice, rwSet);
1268 // Reset data structure for each new execution
1269 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
1270 if (choices == null || choices != icsCG.getAllChoices()) {
1271 // Reset state variables
1273 choices = icsCG.getAllChoices();
1274 refChoices = copyChoices(choices);
1275 // Clear data structures
1276 currVisitedStates.clear();
1277 stateToEventMap.clear();
1278 isEndOfExecution = false;
1282 // Set a backtrack point for a particular state
1283 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
1284 // Set a backtrack CG based on a state ID
1285 LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
1286 BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
1287 backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
1288 backtrackCG.setStateId(stateId);
1289 backtrackCG.reset();
1290 // Update current execution with this new execution
1291 Execution newExecution = new Execution();
1292 TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
1293 newExecution.addTransition(firstTransition);
1294 // Try to free some memory since this map is only used for the current execution
1295 currentExecution.clearCGToChoiceMap();
1296 currentExecution = newExecution;
1297 // Remove from the queue if we don't have more backtrack points for that state
1298 if (backtrackExecutions.isEmpty()) {
1299 backtrackMap.remove(stateId);
1300 backtrackStateQ.remove(stateId);
1304 // Update backtrack sets
1305 // 1) recursively, and
1306 // 2) track accesses per memory location (per shared variable/field)
1307 private void updateBacktrackSet(Execution execution, int currentChoice) {
1308 // Copy ReadWriteSet object
1309 HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
1310 ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice);
1311 if (currRWSet == null) {
1314 currRWSet = currRWSet.getCopy();
1315 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1316 HashSet<TransitionEvent> visited = new HashSet<>();
1317 // Conflict TransitionEvent is essentially the current TransitionEvent
1318 TransitionEvent confTrans = execution.getExecutionTrace().get(currentChoice);
1319 // Update backtrack set recursively
1320 updateBacktrackSetDFS(execution, currentChoice, confTrans.getChoice(), currRWSet, visited);
1323 private void updateBacktrackSetDFS(Execution execution, int currentChoice, int conflictEventChoice,
1324 ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
1325 TransitionEvent currTrans = execution.getExecutionTrace().get(currentChoice);
1326 // Record this transition into the state summary of main summary
1327 currRWSet = mainSummary.updateStateSummary(currTrans.getStateId(), conflictEventChoice, currRWSet);
1328 // Halt when we have visited this transition (in a cycle)
1329 if (visited.contains(currTrans)) {
1332 visited.add(currTrans);
1333 // Check the predecessors only if the set is not empty
1334 if (!currRWSet.isEmpty()) {
1335 // Explore all predecessors
1336 for (Predecessor predecessor : getPredecessors(currTrans.getStateId())) {
1337 // Get the predecessor (previous conflict choice)
1338 int predecessorChoice = predecessor.getChoice();
1339 Execution predecessorExecution = predecessor.getExecution();
1340 // Push up one happens-before transition
1341 int newConflictEventChoice = conflictEventChoice;
1342 // Check if a conflict is found
1343 ReadWriteSet newCurrRWSet = currRWSet.getCopy();
1344 if (isConflictFound(conflictEventChoice, predecessorExecution, predecessorChoice, newCurrRWSet)) {
1345 createBacktrackingPoint(conflictEventChoice, predecessorExecution, predecessorChoice);
1346 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1347 newConflictEventChoice = predecessorExecution.getExecutionTrace().get(predecessorChoice).getChoice();
1349 // Continue performing DFS if conflict is not found
1350 updateBacktrackSetDFS(predecessorExecution, predecessorChoice, newConflictEventChoice,
1351 newCurrRWSet, visited);
1356 // --- Functions related to the reachability analysis when there is a state match
1358 private void addPredecessorToRevisitedState(int stateId) {
1359 // Perform this analysis only when:
1360 // 1) this is not during a switch to a new execution,
1361 // 2) at least 2 choices/events have been explored (choiceCounter > 1),
1362 // 3) state > 0 (state 0 is for boolean CG)
1363 if (!isEndOfExecution && choiceCounter > 1 && stateId > 0) {
1364 if ((currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) ||
1365 prevVisitedStates.contains(stateId)) {
1366 // Record a new predecessor for a revisited state
1367 addPredecessors(stateId);
1372 // Update the backtrack sets from previous executions
1373 private void updateBacktrackSetsFromGraph(int stateId, Execution currExecution, int currChoice) {
1374 // Get events/choices at this state ID
1375 Set<Integer> eventChoicesAtStateId = mainSummary.getEventChoicesAtStateId(stateId);
1376 for (Integer eventChoice : eventChoicesAtStateId) {
1377 // Get the ReadWriteSet object for this event at state ID
1378 ReadWriteSet rwSet = mainSummary.getRWSetForEventChoiceAtState(eventChoice, stateId).getCopy();
1379 // We have to first check for conflicts between the event and the current transition
1380 // Push up one happens-before transition
1381 int conflictEventChoice = eventChoice;
1382 if (isConflictFound(eventChoice, currExecution, currChoice, rwSet)) {
1383 createBacktrackingPoint(eventChoice, currExecution, currChoice);
1384 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1385 conflictEventChoice = currExecution.getExecutionTrace().get(currChoice).getChoice();
1387 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1388 HashSet<TransitionEvent> visited = new HashSet<>();
1389 // Update the backtrack sets recursively
1390 updateBacktrackSetDFS(currExecution, currChoice, conflictEventChoice, rwSet, visited);