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 long startTime;
50 private boolean verboseMode;
51 private boolean stateReductionMode;
52 private final PrintWriter out;
53 private PrintWriter fileWriter;
54 private String detail;
57 private Transition transition;
59 // DPOR-related fields
61 private Integer[] choices;
62 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
63 private int choiceCounter;
64 private int maxEventChoice;
65 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
66 private HashMap<Integer,Integer> currVisitedStates; // States visited in the current execution (maps to frequency)
67 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
68 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
69 private HashSet<ClassInfo> nonRelevantClasses;// Class info objects of non-relevant classes
70 private HashSet<FieldInfo> nonRelevantFields; // Field info objects of non-relevant fields
71 private HashSet<FieldInfo> relevantFields; // Field info objects of relevant fields
72 private HashMap<Integer, HashSet<Integer>> stateToEventMap; // Map state ID to events
73 // Data structure to analyze field Read/Write accesses and conflicts
74 private HashMap<Integer, LinkedList<BacktrackExecution>> backtrackMap; // Track created backtracking points
75 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
76 private Execution currentExecution; // Holds the information about the current execution
77 private HashMap<Integer, HashSet<Integer>> doneBacktrackMap; // Record state ID and trace already constructed
78 private MainSummary mainSummary; // Main summary (M) for state ID, event, and R/W set
79 private HashMap<Integer, PredecessorInfo> stateToPredInfo; // Predecessor info indexed by state ID
80 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
81 private RGraph rGraph; // R-Graph for past executions
84 private boolean isBooleanCGFlipped;
85 private boolean isEndOfExecution;
86 private boolean isNotCheckedForEventsYet;
89 private int numOfTransitions;
90 private HashMap<Integer, HashSet<Integer>> stateToUniqueTransMap;
92 public DPORStateReducerWithSummary(Config config, JPF jpf) {
93 verboseMode = config.getBoolean("printout_state_transition", false);
94 stateReductionMode = config.getBoolean("activate_state_reduction", true);
96 out = new PrintWriter(System.out, true);
100 String outputFile = config.getString("file_output");
101 if (!outputFile.isEmpty()) {
103 fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
104 } catch (IOException e) {
107 isBooleanCGFlipped = false;
108 isNotCheckedForEventsYet = true;
109 mainSummary = new MainSummary();
110 numOfTransitions = 0;
111 nonRelevantClasses = new HashSet<>();
112 nonRelevantFields = new HashSet<>();
113 relevantFields = new HashSet<>();
114 restorableStateMap = new HashMap<>();
115 stateToPredInfo = new HashMap<>();
116 stateToUniqueTransMap = new HashMap<>();
117 initializeStatesVariables();
119 // Timeout input from config is in minutes, so we need to convert into millis
120 timeout = config.getInt("timeout", 0) * 60 * 1000;
121 startTime = System.currentTimeMillis();
125 public void stateRestored(Search search) {
127 id = search.getStateId();
128 depth = search.getDepth();
129 transition = search.getTransition();
131 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
132 " and depth: " + depth + "\n");
137 public void searchStarted(Search search) {
139 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
144 public void stateAdvanced(Search search) {
146 id = search.getStateId();
147 depth = search.getDepth();
148 transition = search.getTransition();
149 if (search.isNewState()) {
155 if (search.isEndState()) {
156 out.println("\n==> DEBUG: This is the last state!\n");
159 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
160 " which is " + detail + " Transition: " + transition + "\n");
162 if (stateReductionMode) {
163 updateStateInfo(search);
168 public void stateBacktracked(Search search) {
170 id = search.getStateId();
171 depth = search.getDepth();
172 transition = search.getTransition();
175 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
176 " and depth: " + depth + "\n");
178 if (stateReductionMode) {
179 updateStateInfo(search);
183 static Logger log = JPF.getLogger("report");
186 public void searchFinished(Search search) {
188 int summaryOfUniqueTransitions = summarizeUniqueTransitions();
189 out.println("\n==> DEBUG: ----------------------------------- search finished");
190 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
191 if (choices != null) {
192 out.println("\n==> DEBUG: Number of events : " + choices.length);
194 // Without DPOR we don't have choices being assigned with a CG
195 out.println("\n==> DEBUG: Number of events : 0");
197 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
198 out.println("\n==> DEBUG: Number of unique transitions (DPOR) : " + summaryOfUniqueTransitions);
199 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
201 fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
202 if (choices != null) {
203 fileWriter.println("==> DEBUG: Number of events : " + choices.length);
205 // Without DPOR we don't have choices being assigned with a CG
206 fileWriter.println("==> DEBUG: Number of events : 0");
208 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
209 fileWriter.println("==> DEBUG: Number of unique transitions (DPOR) : " + summaryOfUniqueTransitions);
210 fileWriter.println();
216 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
217 if (isNotCheckedForEventsYet) {
218 // Check if this benchmark has no events
219 if (nextCG instanceof IntChoiceFromSet) {
220 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
221 Integer[] cgChoices = icsCG.getAllChoices();
222 if (cgChoices.length == 2 && cgChoices[0] == 0 && cgChoices[1] == -1) {
223 // This means the benchmark only has 2 choices, i.e., 0 and -1 which means that it has no events
224 stateReductionMode = false;
226 isNotCheckedForEventsYet = false;
229 if (stateReductionMode) {
230 // Initialize with necessary information from the CG
231 if (nextCG instanceof IntChoiceFromSet) {
232 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
233 // Tell JPF that we are performing DPOR
235 if (!isEndOfExecution) {
236 // Check if CG has been initialized, otherwise initialize it
237 Integer[] cgChoices = icsCG.getAllChoices();
238 // Record the events (from choices)
239 if (choices == null) {
241 // Make a copy of choices as reference
242 refChoices = copyChoices(choices);
243 // Record the max event choice (the last element of the choice array)
244 maxEventChoice = choices[choices.length - 1];
246 icsCG.setNewValues(choices);
248 // Use a modulo since choiceCounter is going to keep increasing
249 int choiceIndex = choiceCounter % choices.length;
250 icsCG.advance(choices[choiceIndex]);
252 // Set done all CGs while transitioning to a new execution
260 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
261 if (stateReductionMode) {
262 // Check the boolean CG and if it is flipped, we are resetting the analysis
263 if (currentCG instanceof BooleanChoiceGenerator) {
264 if (!isBooleanCGFlipped) {
265 isBooleanCGFlipped = true;
267 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
268 initializeStatesVariables();
271 // Check every choice generated and ensure fair scheduling!
272 if (currentCG instanceof IntChoiceFromSet) {
273 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
274 // If this is a new CG then we need to update data structures
275 resetStatesForNewExecution(icsCG, vm);
276 // If we don't see a fair scheduling of events/choices then we have to enforce it
277 ensureFairSchedulingAndSetupTransition(icsCG, vm);
278 // Update backtrack set of an executed event (transition): one transition before this one
279 updateBacktrackSet(currentExecution, choiceCounter - 1);
280 // Explore the next backtrack point:
281 // 1) if we have seen this state or this state contains cycles that involve all events, and
282 // 2) after the current CG is advanced at least once
283 if (choiceCounter > 0 && terminateCurrentExecution()) {
284 exploreNextBacktrackPoints(vm, icsCG);
286 // We only count IntChoiceFromSet CGs
288 countUniqueTransitions(vm.getStateId(), icsCG.getNextChoice());
290 // Map state to event
291 mapStateToEvent(icsCG.getNextChoice());
292 justVisitedStates.clear();
296 // We only count IntChoiceFromSet CGs
297 if (currentCG instanceof IntChoiceFromSet) {
304 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
307 if (System.currentTimeMillis() - startTime > timeout) {
308 StringBuilder sbTimeOut = new StringBuilder();
309 sbTimeOut.append("Execution timeout: " + (timeout / (60 * 1000)) + " minutes have passed!");
310 Instruction nextIns = ti.createAndThrowException("java.lang.RuntimeException", sbTimeOut.toString());
311 ti.setNextPC(nextIns);
315 if (stateReductionMode) {
316 if (!isEndOfExecution) {
317 // Has to be initialized and it is a integer CG
318 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
319 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
320 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
321 if (currentChoice < 0) { // If choice is -1 then skip
324 currentChoice = checkAndAdjustChoice(currentChoice, vm);
325 // Record accesses from executed instructions
326 if (executedInsn instanceof JVMFieldInstruction) {
327 // We don't care about libraries
328 if (!isFieldExcluded(executedInsn)) {
329 analyzeReadWriteAccesses(executedInsn, currentChoice);
331 } else if (executedInsn instanceof INVOKEINTERFACE) {
332 // Handle the read/write accesses that occur through iterators
333 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
345 // This class compactly stores backtrack execution:
346 // 1) backtrack choice list, and
347 // 2) first backtrack point (linking with predecessor execution)
348 private class BacktrackExecution {
349 private Integer[] choiceList;
350 private TransitionEvent firstTransition;
352 public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
353 choiceList = choList;
354 firstTransition = fTransition;
357 public Integer[] getChoiceList() {
361 public TransitionEvent getFirstTransition() {
362 return firstTransition;
366 // This class stores a representation of an execution
367 // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
368 // TODO: We basically need to keep track of:
369 // TODO: (1) last read/write access to each memory location
370 // TODO: (2) last state with two or more incoming events/transitions
371 private class Execution {
372 private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
373 private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
374 private boolean isNew; // Track if this is the first time it is accessed
375 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
378 cgToChoiceMap = new HashMap<>();
379 executionTrace = new ArrayList<>();
381 readWriteFieldsMap = new HashMap<>();
384 public void addTransition(TransitionEvent newBacktrackPoint) {
385 executionTrace.add(newBacktrackPoint);
388 public void clearCGToChoiceMap() {
389 cgToChoiceMap = null;
392 public int getChoiceFromCG(IntChoiceFromSet icsCG) {
393 return cgToChoiceMap.get(icsCG);
396 public ArrayList<TransitionEvent> getExecutionTrace() {
397 return executionTrace;
400 public TransitionEvent getFirstTransition() {
401 return executionTrace.get(0);
404 public TransitionEvent getLastTransition() {
405 return executionTrace.get(executionTrace.size() - 1);
408 public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
409 return readWriteFieldsMap;
412 public boolean isNew() {
414 // Right after this is accessed, it is no longer new
421 public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
422 cgToChoiceMap.put(icsCG, choice);
426 // This class compactly stores a predecessor
427 // 1) a predecessor execution
428 // 2) the predecessor choice in that predecessor execution
429 private class Predecessor {
430 private int choice; // Predecessor choice
431 private Execution execution; // Predecessor execution
433 public Predecessor(int predChoice, Execution predExec) {
435 execution = predExec;
438 public int getChoice() {
442 public Execution getExecution() {
447 // This class represents a R-Graph (in the paper it is a state transition graph R)
448 // This implementation stores reachable transitions from and connects with past executions
449 private class RGraph {
450 private int hiStateId; // Maximum state Id
451 private HashMap<Integer, HashSet<TransitionEvent>> graph; // Reachable transitions from past executions
455 graph = new HashMap<>();
458 public void addReachableTransition(int stateId, TransitionEvent transition) {
459 HashSet<TransitionEvent> transitionSet;
460 if (graph.containsKey(stateId)) {
461 transitionSet = graph.get(stateId);
463 transitionSet = new HashSet<>();
464 graph.put(stateId, transitionSet);
466 // Insert into the set if it does not contain it yet
467 if (!transitionSet.contains(transition)) {
468 transitionSet.add(transition);
470 // Update highest state ID
471 if (hiStateId < stateId) {
476 public HashSet<TransitionEvent> getReachableTransitionsAtState(int stateId) {
477 if (!graph.containsKey(stateId)) {
478 // This is a loop from a transition to itself, so just return the current transition
479 HashSet<TransitionEvent> transitionSet = new HashSet<>();
480 transitionSet.add(currentExecution.getLastTransition());
481 return transitionSet;
483 return graph.get(stateId);
486 public HashSet<TransitionEvent> getReachableTransitions(int stateId) {
487 HashSet<TransitionEvent> reachableTransitions = new HashSet<>();
488 // All transitions from states higher than the given state ID (until the highest state ID) are reachable
489 for(int stId = stateId; stId <= hiStateId; stId++) {
490 // We might encounter state IDs from the first round of Boolean CG
491 // The second round of Boolean CG should consider these new states
492 if (graph.containsKey(stId)) {
493 reachableTransitions.addAll(graph.get(stId));
496 return reachableTransitions;
500 // This class compactly stores Read and Write field sets
501 // We store the field name and its object ID
502 // Sharing the same field means the same field name and object ID
503 private class ReadWriteSet {
504 private HashMap<String, Integer> readMap;
505 private HashMap<String, Integer> writeMap;
507 public ReadWriteSet() {
508 readMap = new HashMap<>();
509 writeMap = new HashMap<>();
512 public void addReadField(String field, int objectId) {
513 readMap.put(field, objectId);
516 public void addWriteField(String field, int objectId) {
517 writeMap.put(field, objectId);
520 public void removeReadField(String field) {
521 readMap.remove(field);
524 public void removeWriteField(String field) {
525 writeMap.remove(field);
528 public boolean isEmpty() {
529 return readMap.isEmpty() && writeMap.isEmpty();
532 public ReadWriteSet getCopy() {
533 ReadWriteSet copyRWSet = new ReadWriteSet();
534 // Copy the maps in the set into the new object copy
535 copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
536 copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
540 public Set<String> getReadSet() {
541 return readMap.keySet();
544 public Set<String> getWriteSet() {
545 return writeMap.keySet();
548 public boolean readFieldExists(String field) {
549 return readMap.containsKey(field);
552 public boolean writeFieldExists(String field) {
553 return writeMap.containsKey(field);
556 public int readFieldObjectId(String field) {
557 return readMap.get(field);
560 public int writeFieldObjectId(String field) {
561 return writeMap.get(field);
564 private HashMap<String, Integer> getReadMap() {
568 private HashMap<String, Integer> getWriteMap() {
572 private void setReadMap(HashMap<String, Integer> rMap) {
576 private void setWriteMap(HashMap<String, Integer> wMap) {
581 // This class is a representation of a state.
582 // It stores the predecessors to a state.
583 // TODO: We also have stateToEventMap, restorableStateMap, and doneBacktrackMap that has state Id as HashMap key.
584 private class PredecessorInfo {
585 private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
586 private HashMap<Execution, HashSet<Integer>> recordedPredecessors;
587 // Memorize event and choice number to not record them twice
589 public PredecessorInfo() {
590 predecessors = new HashSet<>();
591 recordedPredecessors = new HashMap<>();
594 public HashSet<Predecessor> getPredecessors() {
598 private boolean isRecordedPredecessor(Execution execution, int choice) {
599 // See if we have recorded this predecessor earlier
600 HashSet<Integer> recordedChoices;
601 if (recordedPredecessors.containsKey(execution)) {
602 recordedChoices = recordedPredecessors.get(execution);
603 if (recordedChoices.contains(choice)) {
607 recordedChoices = new HashSet<>();
608 recordedPredecessors.put(execution, recordedChoices);
610 // Record the choice if we haven't seen it
611 recordedChoices.add(choice);
616 public void recordPredecessor(Execution execution, int choice) {
617 if (!isRecordedPredecessor(execution, choice)) {
618 predecessors.add(new Predecessor(choice, execution));
623 // This class compactly stores transitions:
627 // 4) predecessors (for backward DFS).
628 private class TransitionEvent {
629 private int choice; // Choice chosen at this transition
630 private int choiceCounter; // Choice counter at this transition
631 private Execution execution; // The execution where this transition belongs
632 private int stateId; // State at this transition
633 private IntChoiceFromSet transitionCG; // CG at this transition
635 public TransitionEvent() {
643 public int getChoice() {
647 public int getChoiceCounter() {
648 return choiceCounter;
651 public Execution getExecution() {
655 public int getStateId() {
659 public IntChoiceFromSet getTransitionCG() { return transitionCG; }
661 public void setChoice(int cho) {
665 public void setChoiceCounter(int choCounter) {
666 choiceCounter = choCounter;
669 public void setExecution(Execution exec) {
673 public void setStateId(int stId) {
677 public void setTransitionCG(IntChoiceFromSet cg) {
682 // -- PRIVATE CLASSES RELATED TO SUMMARY
683 // This class stores the main summary of states
684 // 1) Main mapping between state ID and state summary
685 // 2) State summary is a mapping between events (i.e., event choices) and their respective R/W sets
686 private class MainSummary {
687 private HashMap<Integer, HashMap<Integer, ReadWriteSet>> mainSummary;
689 public MainSummary() {
690 mainSummary = new HashMap<>();
693 public Set<Integer> getEventChoicesAtStateId(int stateId) {
694 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
695 // Return a new set since this might get updated concurrently
696 return new HashSet<>(stateSummary.keySet());
699 public ReadWriteSet getRWSetForEventChoiceAtState(int eventChoice, int stateId) {
700 HashMap<Integer, ReadWriteSet> stateSummary = mainSummary.get(stateId);
701 return stateSummary.get(eventChoice);
704 public Set<Integer> getStateIds() {
705 return mainSummary.keySet();
708 private ReadWriteSet performUnion(ReadWriteSet recordedRWSet, ReadWriteSet rwSet) {
709 // Combine the same write accesses and record in the recordedRWSet
710 HashMap<String, Integer> recordedWriteMap = recordedRWSet.getWriteMap();
711 HashMap<String, Integer> writeMap = rwSet.getWriteMap();
712 for(Map.Entry<String, Integer> entry : recordedWriteMap.entrySet()) {
713 String writeField = entry.getKey();
714 // Remove the entry from rwSet if both field and object ID are the same
715 if (writeMap.containsKey(writeField) &&
716 (writeMap.get(writeField).equals(recordedWriteMap.get(writeField)))) {
717 writeMap.remove(writeField);
720 // Then add the rest (fields in rwSet but not in recordedRWSet)
721 // into the recorded map because these will be traversed
722 recordedWriteMap.putAll(writeMap);
723 // Combine the same read accesses and record in the recordedRWSet
724 HashMap<String, Integer> recordedReadMap = recordedRWSet.getReadMap();
725 HashMap<String, Integer> readMap = rwSet.getReadMap();
726 for(Map.Entry<String, Integer> entry : recordedReadMap.entrySet()) {
727 String readField = entry.getKey();
728 // Remove the entry from rwSet if both field and object ID are the same
729 if (readMap.containsKey(readField) &&
730 (readMap.get(readField).equals(recordedReadMap.get(readField)))) {
731 readMap.remove(readField);
734 // Then add the rest (fields in rwSet but not in recordedRWSet)
735 // into the recorded map because these will be traversed
736 recordedReadMap.putAll(readMap);
741 public ReadWriteSet updateStateSummary(int stateId, int eventChoice, ReadWriteSet rwSet) {
742 // If the state Id has not existed, insert the StateSummary object
743 // If the state Id has existed, find the event choice:
744 // 1) If the event choice has not existed, insert the ReadWriteSet object
745 // 2) If the event choice has existed, perform union between the two ReadWriteSet objects
746 if (!rwSet.isEmpty()) {
747 HashMap<Integer, ReadWriteSet> stateSummary;
748 if (!mainSummary.containsKey(stateId)) {
749 stateSummary = new HashMap<>();
750 stateSummary.put(eventChoice, rwSet.getCopy());
751 mainSummary.put(stateId, stateSummary);
753 stateSummary = mainSummary.get(stateId);
754 if (!stateSummary.containsKey(eventChoice)) {
755 stateSummary.put(eventChoice, rwSet.getCopy());
757 rwSet = performUnion(stateSummary.get(eventChoice), rwSet);
766 private final static String DO_CALL_METHOD = "doCall";
767 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
768 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
769 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
770 // Groovy library created fields
771 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
773 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
774 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
775 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
776 // Java and Groovy libraries
777 { "java", "org", "sun", "com", "gov", "groovy"};
778 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
779 private final static String GET_PROPERTY_METHOD =
780 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
781 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
782 private final static String JAVA_INTEGER = "int";
783 private final static String JAVA_STRING_LIB = "java.lang.String";
786 private Integer[] copyChoices(Integer[] choicesToCopy) {
788 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
789 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
790 return copyOfChoices;
793 private void ensureFairSchedulingAndSetupTransition(IntChoiceFromSet icsCG, VM vm) {
794 // Check the next choice and if the value is not the same as the expected then force the expected value
795 int choiceIndex = choiceCounter % refChoices.length;
796 int nextChoice = icsCG.getNextChoice();
797 if (refChoices[choiceIndex] != nextChoice) {
798 int expectedChoice = refChoices[choiceIndex];
799 int currCGIndex = icsCG.getNextChoiceIndex();
800 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
801 icsCG.setChoice(currCGIndex, expectedChoice);
804 // Get state ID and associate it with this transition
805 int stateId = vm.getStateId();
806 TransitionEvent transition = setupTransition(icsCG, stateId, choiceIndex);
807 // Add new transition to the current execution and map it in R-Graph
808 for (Integer stId : justVisitedStates) { // Map this transition to all the previously passed states
809 rGraph.addReachableTransition(stId, transition);
811 currentExecution.mapCGToChoice(icsCG, choiceCounter);
812 // Store restorable state object for this state (always store the latest)
813 if (!restorableStateMap.containsKey(stateId)) {
814 RestorableVMState restorableState = vm.getRestorableState();
815 restorableStateMap.put(stateId, restorableState);
819 private TransitionEvent setupTransition(IntChoiceFromSet icsCG, int stateId, int choiceIndex) {
820 // Get a new transition
821 TransitionEvent transition;
822 if (currentExecution.isNew()) {
823 // We need to handle the first transition differently because this has a predecessor execution
824 transition = currentExecution.getFirstTransition();
826 transition = new TransitionEvent();
827 currentExecution.addTransition(transition);
828 addPredecessors(stateId);
830 transition.setExecution(currentExecution);
831 transition.setTransitionCG(icsCG);
832 transition.setStateId(stateId);
833 transition.setChoice(refChoices[choiceIndex]);
834 transition.setChoiceCounter(choiceCounter);
839 // --- Functions related to statistics counting
840 // Count unique state IDs
841 private void countUniqueTransitions(int stateId, int nextChoiceValue) {
842 HashSet<Integer> events;
843 // Get the set of events
844 if (!stateToUniqueTransMap.containsKey(stateId)) {
845 events = new HashSet<>();
846 stateToUniqueTransMap.put(stateId, events);
848 events = stateToUniqueTransMap.get(stateId);
851 if (!events.contains(nextChoiceValue)) {
852 events.add(nextChoiceValue);
856 // Summarize unique state IDs
857 private int summarizeUniqueTransitions() {
858 // Just count the set size of each of entry map and sum them up
859 int numOfUniqueTransitions = 0;
860 for (Map.Entry<Integer,HashSet<Integer>> entry : stateToUniqueTransMap.entrySet()) {
861 numOfUniqueTransitions = numOfUniqueTransitions + entry.getValue().size();
864 return numOfUniqueTransitions;
867 // --- Functions related to cycle detection and reachability graph
869 // Detect cycles in the current execution/trace
870 // We terminate the execution iff:
871 // (1) the state has been visited in the current execution
872 // (2) the state has one or more cycles that involve all the events
873 // With simple approach we only need to check for a re-visited state.
874 // Basically, we have to check that we have executed all events between two occurrences of such state.
875 private boolean completeFullCycle(int stId) {
876 // False if the state ID hasn't been recorded
877 if (!stateToEventMap.containsKey(stId)) {
880 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
881 // Check if this set contains all the event choices
882 // If not then this is not the terminating condition
883 for(int i=0; i<=maxEventChoice; i++) {
884 if (!visitedEvents.contains(i)) {
891 private void initializeStatesVariables() {
898 if (!isBooleanCGFlipped) {
899 currVisitedStates = new HashMap<>();
900 justVisitedStates = new HashSet<>();
901 prevVisitedStates = new HashSet<>();
902 stateToEventMap = new HashMap<>();
904 currVisitedStates.clear();
905 justVisitedStates.clear();
906 prevVisitedStates.clear();
907 stateToEventMap.clear();
910 if (!isBooleanCGFlipped) {
911 backtrackMap = new HashMap<>();
913 backtrackMap.clear();
915 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
916 currentExecution = new Execution();
917 currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
918 if (!isBooleanCGFlipped) {
919 doneBacktrackMap = new HashMap<>();
921 doneBacktrackMap.clear();
923 rGraph = new RGraph();
925 isEndOfExecution = false;
928 private void mapStateToEvent(int nextChoiceValue) {
929 // Update all states with this event/choice
930 // This means that all past states now see this transition
931 Set<Integer> stateSet = stateToEventMap.keySet();
932 for(Integer stateId : stateSet) {
933 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
934 eventSet.add(nextChoiceValue);
938 private boolean terminateCurrentExecution() {
939 // We need to check all the states that have just been visited
940 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
941 boolean terminate = false;
942 Set<Integer> mainStateIds = mainSummary.getStateIds();
943 for(Integer stateId : justVisitedStates) {
944 // We exclude states that are produced by other CGs that are not integer CG
945 // When we encounter these states, then we should also encounter the corresponding integer CG state ID
946 if (mainStateIds.contains(stateId)) {
947 // We perform updates on backtrack sets for every
948 if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
949 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
952 // If frequency > 1 then this means we have visited this stateId more than once in the current execution
953 if (currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) {
954 updateBacktrackSetsFromGraph(stateId, currentExecution, choiceCounter - 1);
961 private void updateStateInfo(Search search) {
962 // Update the state variables
963 int stateId = search.getStateId();
964 // Insert state ID into the map if it is new
965 if (!stateToEventMap.containsKey(stateId)) {
966 HashSet<Integer> eventSet = new HashSet<>();
967 stateToEventMap.put(stateId, eventSet);
969 addPredecessorToRevisitedState(stateId);
970 justVisitedStates.add(stateId);
971 if (!prevVisitedStates.contains(stateId)) {
972 // It is a currently visited states if the state has not been seen in previous executions
974 if (currVisitedStates.containsKey(stateId)) {
975 frequency = currVisitedStates.get(stateId);
977 currVisitedStates.put(stateId, frequency + 1); // Increment frequency counter
981 // --- Functions related to Read/Write access analysis on shared fields
983 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList, TransitionEvent conflictTransition) {
984 // Insert backtrack point to the right state ID
985 LinkedList<BacktrackExecution> backtrackExecList;
986 if (backtrackMap.containsKey(stateId)) {
987 backtrackExecList = backtrackMap.get(stateId);
989 backtrackExecList = new LinkedList<>();
990 backtrackMap.put(stateId, backtrackExecList);
992 // Add the new backtrack execution object
993 TransitionEvent backtrackTransition = new TransitionEvent();
994 backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
995 // Add to priority queue
996 if (!backtrackStateQ.contains(stateId)) {
997 backtrackStateQ.add(stateId);
1001 private void addPredecessors(int stateId) {
1002 PredecessorInfo predecessorInfo;
1003 if (!stateToPredInfo.containsKey(stateId)) {
1004 predecessorInfo = new PredecessorInfo();
1005 stateToPredInfo.put(stateId, predecessorInfo);
1006 } else { // This is a new state Id
1007 predecessorInfo = stateToPredInfo.get(stateId);
1009 predecessorInfo.recordPredecessor(currentExecution, choiceCounter - 1);
1012 // Analyze Read/Write accesses that are directly invoked on fields
1013 private void analyzeReadWriteAccesses(Instruction executedInsn, int currentChoice) {
1014 // Get the field info
1015 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
1016 // Analyze only after being initialized
1017 String fieldClass = fieldInfo.getFullName();
1018 // Do the analysis to get Read and Write accesses to fields
1019 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
1020 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
1021 // Record the field in the map
1022 if (executedInsn instanceof WriteInstruction) {
1023 // We first check the non-relevant fields set
1024 if (!nonRelevantFields.contains(fieldInfo)) {
1025 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
1026 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
1027 if (fieldClass.startsWith(str)) {
1028 nonRelevantFields.add(fieldInfo);
1033 // If we have this field in the non-relevant fields set then we return right away
1036 rwSet.addWriteField(fieldClass, objectId);
1037 } else if (executedInsn instanceof ReadInstruction) {
1038 rwSet.addReadField(fieldClass, objectId);
1042 // Analyze Read accesses that are indirect (performed through iterators)
1043 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
1044 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
1046 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
1047 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
1048 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
1049 // Extract info from the stack frame
1050 StackFrame frame = ti.getTopFrame();
1051 int[] frameSlots = frame.getSlots();
1052 // Get the Groovy callsite library at index 0
1053 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
1054 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
1057 // Get the iterated object whose property is accessed
1058 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
1059 if (eiAccessObj == null) {
1062 // We exclude library classes (they start with java, org, etc.) and some more
1063 ClassInfo classInfo = eiAccessObj.getClassInfo();
1064 String objClassName = classInfo.getName();
1065 // Check if this class info is part of the non-relevant classes set already
1066 if (!nonRelevantClasses.contains(classInfo)) {
1067 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName) ||
1068 excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName)) {
1069 nonRelevantClasses.add(classInfo);
1073 // If it is part of the non-relevant classes set then return immediately
1076 // Extract fields from this object and put them into the read write
1077 int numOfFields = eiAccessObj.getNumberOfFields();
1078 for(int i=0; i<numOfFields; i++) {
1079 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
1080 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
1081 String fieldClass = fieldInfo.getFullName();
1082 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
1083 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
1084 // Record the field in the map
1085 rwSet.addReadField(fieldClass, objectId);
1091 private int checkAndAdjustChoice(int currentChoice, VM vm) {
1092 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
1093 // for certain method calls in the infrastructure, e.g., eventSince()
1094 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
1095 // This is the main event CG
1096 if (currentCG instanceof IntIntervalGenerator) {
1097 // This is the interval CG used in device handlers
1098 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
1099 // Iterate until we find the IntChoiceFromSet CG
1100 while (!(parentCG instanceof IntChoiceFromSet)) {
1101 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
1103 // Find the choice related to the IntIntervalGenerator CG from the map
1104 currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
1106 return currentChoice;
1109 private void createBacktrackingPoint(int eventChoice, Execution conflictExecution, int conflictChoice) {
1110 // Create a new list of choices for backtrack based on the current choice and conflicting event number
1111 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
1112 // for the original set {0, 1, 2, 3}
1114 // eventChoice represents the event/transaction that will be put into the backtracking set of
1115 // conflictExecution/conflictChoice
1116 Integer[] newChoiceList = new Integer[refChoices.length];
1117 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1118 int stateId = conflictTrace.get(conflictChoice).getStateId();
1119 // Check if this trace has been done from this state
1120 if (isTraceAlreadyConstructed(eventChoice, stateId)) {
1123 // Put the conflicting event numbers first and reverse the order
1124 newChoiceList[0] = eventChoice;
1125 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
1126 for (int i = 0, j = 1; i < refChoices.length; i++) {
1127 if (refChoices[i] != newChoiceList[0]) {
1128 newChoiceList[j] = refChoices[i];
1132 // Predecessor of the new backtrack point is the same as the conflict point's
1133 addNewBacktrackPoint(stateId, newChoiceList, conflictTrace.get(conflictChoice));
1136 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
1137 for (String excludedField : excludedStrings) {
1138 if (className.contains(excludedField)) {
1145 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
1146 for (String excludedField : excludedStrings) {
1147 if (className.endsWith(excludedField)) {
1154 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
1155 for (String excludedField : excludedStrings) {
1156 if (className.startsWith(excludedField)) {
1163 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
1164 // Check if we are reaching the end of our execution: no more backtracking points to explore
1165 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
1166 if (!backtrackStateQ.isEmpty()) {
1167 // Set done all the other backtrack points
1168 for (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
1169 backtrackTransition.getTransitionCG().setDone();
1171 // Reset the next backtrack point with the latest state
1172 int hiStateId = backtrackStateQ.peek();
1173 // Restore the state first if necessary
1174 if (vm.getStateId() != hiStateId) {
1175 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
1176 vm.restoreState(restorableState);
1178 // Set the backtrack CG
1179 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
1180 setBacktrackCG(hiStateId, backtrackCG);
1182 // Set done this last CG (we save a few rounds)
1185 // Save all the visited states when starting a new execution of trace
1186 prevVisitedStates.addAll(currVisitedStates.keySet());
1187 // This marks a transitional period to the new CG
1188 isEndOfExecution = true;
1191 private boolean isConflictFound(int eventChoice, Execution conflictExecution, int conflictChoice,
1192 ReadWriteSet currRWSet) {
1193 // conflictExecution/conflictChoice represent a predecessor event/transaction that can potentially have a conflict
1194 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1195 HashMap<Integer, ReadWriteSet> confRWFieldsMap = conflictExecution.getReadWriteFieldsMap();
1196 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
1197 if (!confRWFieldsMap.containsKey(conflictChoice) || eventChoice == conflictTrace.get(conflictChoice).getChoice()) {
1200 // R/W set of choice/event that may have a potential conflict
1201 ReadWriteSet confRWSet = confRWFieldsMap.get(conflictChoice);
1202 // Check for conflicts with Read and Write fields for Write instructions
1203 Set<String> currWriteSet = currRWSet.getWriteSet();
1204 for(String writeField : currWriteSet) {
1205 int currObjId = currRWSet.writeFieldObjectId(writeField);
1206 if ((confRWSet.readFieldExists(writeField) && confRWSet.readFieldObjectId(writeField) == currObjId) ||
1207 (confRWSet.writeFieldExists(writeField) && confRWSet.writeFieldObjectId(writeField) == currObjId)) {
1208 // Remove this from the write set as we are tracking per memory location
1209 currRWSet.removeWriteField(writeField);
1213 // Check for conflicts with Write fields for Read instructions
1214 Set<String> currReadSet = currRWSet.getReadSet();
1215 for(String readField : currReadSet) {
1216 int currObjId = currRWSet.readFieldObjectId(readField);
1217 if (confRWSet.writeFieldExists(readField) && confRWSet.writeFieldObjectId(readField) == currObjId) {
1218 // Remove this from the read set as we are tracking per memory location
1219 currRWSet.removeReadField(readField);
1223 // Return false if no conflict is found
1227 private boolean isFieldExcluded(Instruction executedInsn) {
1228 // Get the field info
1229 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
1230 // Check if the non-relevant fields set already has it
1231 if (nonRelevantFields.contains(fieldInfo)) {
1234 // Check if the relevant fields set already has it
1235 if (relevantFields.contains(fieldInfo)) {
1238 // Analyze only after being initialized
1239 String field = fieldInfo.getFullName();
1240 // Check against "starts-with", "ends-with", and "contains" list
1241 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
1242 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
1243 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
1244 nonRelevantFields.add(fieldInfo);
1247 relevantFields.add(fieldInfo);
1251 // Check if this trace is already constructed
1252 private boolean isTraceAlreadyConstructed(int firstChoice, int stateId) {
1253 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
1254 // Check if the trace has been constructed as a backtrack point for this state
1255 // TODO: THIS IS AN OPTIMIZATION!
1256 HashSet<Integer> choiceSet;
1257 if (doneBacktrackMap.containsKey(stateId)) {
1258 choiceSet = doneBacktrackMap.get(stateId);
1259 if (choiceSet.contains(firstChoice)) {
1263 choiceSet = new HashSet<>();
1264 doneBacktrackMap.put(stateId, choiceSet);
1266 choiceSet.add(firstChoice);
1271 private HashSet<Predecessor> getPredecessors(int stateId) {
1272 // Get a set of predecessors for this state ID
1273 HashSet<Predecessor> predecessors;
1274 if (stateToPredInfo.containsKey(stateId)) {
1275 PredecessorInfo predecessorInfo = stateToPredInfo.get(stateId);
1276 predecessors = predecessorInfo.getPredecessors();
1278 predecessors = new HashSet<>();
1281 return predecessors;
1284 private ReadWriteSet getReadWriteSet(int currentChoice) {
1285 // Do the analysis to get Read and Write accesses to fields
1287 // We already have an entry
1288 HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
1289 if (currReadWriteFieldsMap.containsKey(currentChoice)) {
1290 rwSet = currReadWriteFieldsMap.get(currentChoice);
1291 } else { // We need to create a new entry
1292 rwSet = new ReadWriteSet();
1293 currReadWriteFieldsMap.put(currentChoice, rwSet);
1298 // Reset data structure for each new execution
1299 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
1300 if (choices == null || choices != icsCG.getAllChoices()) {
1301 // Reset state variables
1303 choices = icsCG.getAllChoices();
1304 refChoices = copyChoices(choices);
1305 // Clear data structures
1306 currVisitedStates.clear();
1307 stateToEventMap.clear();
1308 isEndOfExecution = false;
1312 // Set a backtrack point for a particular state
1313 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
1314 // Set a backtrack CG based on a state ID
1315 LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
1316 BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
1317 backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
1318 backtrackCG.setStateId(stateId);
1319 backtrackCG.reset();
1320 // Update current execution with this new execution
1321 Execution newExecution = new Execution();
1322 TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
1323 newExecution.addTransition(firstTransition);
1324 // Try to free some memory since this map is only used for the current execution
1325 currentExecution.clearCGToChoiceMap();
1326 currentExecution = newExecution;
1327 // Remove from the queue if we don't have more backtrack points for that state
1328 if (backtrackExecutions.isEmpty()) {
1329 backtrackMap.remove(stateId);
1330 backtrackStateQ.remove(stateId);
1334 // Update backtrack sets
1335 // 1) recursively, and
1336 // 2) track accesses per memory location (per shared variable/field)
1337 private void updateBacktrackSet(Execution execution, int currentChoice) {
1338 // Copy ReadWriteSet object
1339 HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
1340 ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice);
1341 if (currRWSet == null) {
1344 currRWSet = currRWSet.getCopy();
1345 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1346 HashSet<TransitionEvent> visited = new HashSet<>();
1347 // Conflict TransitionEvent is essentially the current TransitionEvent
1348 TransitionEvent confTrans = execution.getExecutionTrace().get(currentChoice);
1349 // Update backtrack set recursively
1350 updateBacktrackSetDFS(execution, currentChoice, confTrans.getChoice(), currRWSet, visited);
1353 private void updateBacktrackSetDFS(Execution execution, int currentChoice, int conflictEventChoice,
1354 ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
1355 TransitionEvent currTrans = execution.getExecutionTrace().get(currentChoice);
1356 // Record this transition into the state summary of main summary
1357 currRWSet = mainSummary.updateStateSummary(currTrans.getStateId(), conflictEventChoice, currRWSet);
1358 // Halt when we have visited this transition (in a cycle)
1359 if (visited.contains(currTrans)) {
1362 visited.add(currTrans);
1363 // Check the predecessors only if the set is not empty
1364 if (!currRWSet.isEmpty()) {
1365 // Explore all predecessors
1366 for (Predecessor predecessor : getPredecessors(currTrans.getStateId())) {
1367 // Get the predecessor (previous conflict choice)
1368 int predecessorChoice = predecessor.getChoice();
1369 Execution predecessorExecution = predecessor.getExecution();
1370 // Push up one happens-before transition
1371 int newConflictEventChoice = conflictEventChoice;
1372 // Check if a conflict is found
1373 ReadWriteSet newCurrRWSet = currRWSet.getCopy();
1374 if (isConflictFound(conflictEventChoice, predecessorExecution, predecessorChoice, newCurrRWSet)) {
1375 createBacktrackingPoint(conflictEventChoice, predecessorExecution, predecessorChoice);
1376 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1377 newConflictEventChoice = predecessorExecution.getExecutionTrace().get(predecessorChoice).getChoice();
1379 // Continue performing DFS if conflict is not found
1380 updateBacktrackSetDFS(predecessorExecution, predecessorChoice, newConflictEventChoice,
1381 newCurrRWSet, visited);
1386 // --- Functions related to the reachability analysis when there is a state match
1388 private void addPredecessorToRevisitedState(int stateId) {
1389 // Perform this analysis only when:
1390 // 1) this is not during a switch to a new execution,
1391 // 2) at least 2 choices/events have been explored (choiceCounter > 1),
1392 // 3) state > 0 (state 0 is for boolean CG)
1393 if (!isEndOfExecution && choiceCounter > 1 && stateId > 0) {
1394 if ((currVisitedStates.containsKey(stateId) && currVisitedStates.get(stateId) > 1) ||
1395 prevVisitedStates.contains(stateId)) {
1396 // Record a new predecessor for a revisited state
1397 addPredecessors(stateId);
1402 // Update the backtrack sets from previous executions
1403 private void updateBacktrackSetsFromGraph(int stateId, Execution currExecution, int currChoice) {
1404 // Get events/choices at this state ID
1405 Set<Integer> eventChoicesAtStateId = mainSummary.getEventChoicesAtStateId(stateId);
1406 for (Integer eventChoice : eventChoicesAtStateId) {
1407 // Get the ReadWriteSet object for this event at state ID
1408 ReadWriteSet rwSet = mainSummary.getRWSetForEventChoiceAtState(eventChoice, stateId).getCopy();
1409 // We have to first check for conflicts between the event and the current transition
1410 // Push up one happens-before transition
1411 int conflictEventChoice = eventChoice;
1412 if (isConflictFound(eventChoice, currExecution, currChoice, rwSet)) {
1413 createBacktrackingPoint(eventChoice, currExecution, currChoice);
1414 // We need to extract the pushed happens-before event choice from the predecessor execution and choice
1415 conflictEventChoice = currExecution.getExecutionTrace().get(currChoice).getChoice();
1417 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1418 HashSet<TransitionEvent> visited = new HashSet<>();
1419 // Update the backtrack sets recursively
1420 updateBacktrackSetDFS(currExecution, currChoice, conflictEventChoice, rwSet, visited);