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.search.Search;
24 import gov.nasa.jpf.jvm.bytecode.*;
25 import gov.nasa.jpf.vm.*;
26 import gov.nasa.jpf.vm.bytecode.ReadInstruction;
27 import gov.nasa.jpf.vm.bytecode.WriteInstruction;
28 import gov.nasa.jpf.vm.choice.IntChoiceFromSet;
30 import java.io.PrintWriter;
34 // TODO: Fix for Groovy's model-checking
35 // TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
37 * Simple tool to log state changes.
39 * This DPOR implementation is augmented by the algorithm presented in this SPIN paper:
40 * http://spinroot.com/spin/symposia/ws08/spin2008_submission_33.pdf
42 * The algorithm is presented on page 11 of the paper. Basically, we create a graph G
43 * (i.e., visible operation dependency graph)
44 * that maps inter-related threads/sub-programs that trigger state changes.
45 * The key to this approach is that we evaluate graph G in every iteration/recursion to
46 * only update the backtrack sets of the threads/sub-programs that are reachable in graph G
47 * from the currently running thread/sub-program.
49 public class StateReducer extends ListenerAdapter {
52 private boolean debugMode;
53 private boolean stateReductionMode;
54 private final PrintWriter out;
55 private String detail;
58 private Transition transition;
60 // State reduction fields
61 private Integer[] choices;
62 private Integer[] refChoices;
63 private IntChoiceFromSet currCG;
64 private int choiceCounter;
65 private Integer choiceUpperBound;
66 private Integer maxUpperBound;
67 private boolean isInitialized;
68 private boolean isResetAfterAnalysis;
69 private boolean isBooleanCGFlipped;
70 private HashMap<IntChoiceFromSet, Integer> cgMap;
71 // Record the mapping between event number and field accesses (Read and Write)
72 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
73 // The following is the backtrack map (set) that stores all the backtrack information
74 // e.g., event number 1 can have two backtrack sequences: {3,1,2,4,...} and {2,1,3,4,...}
75 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap;
76 // Stores explored backtrack lists in the form of HashSet of Strings
77 private HashSet<String> backtrackSet;
78 private HashMap<Integer, HashSet<Integer>> conflictPairMap;
80 // Map that represents graph G
81 // (i.e., visible operation dependency graph (VOD Graph)
82 private HashMap<Integer, HashSet<Integer>> vodGraphMap;
83 // Set that represents hash table H
84 // (i.e., hash table that records encountered states)
85 // VOD graph is updated when the state has not yet been seen
87 private HashSet<Integer> justVisitedStates;
88 // Previous choice number
89 private int prevChoiceValue;
90 // HashSet that stores references to unused CGs
91 private HashSet<IntChoiceFromSet> unusedCG;
93 //private HashMap<Integer, ConflictTracker.Node> stateGraph;
94 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
96 // Visited states in the previous and current executions/traces for terminating condition
97 private HashSet<Integer> prevVisitedStates;
98 private HashSet<Integer> currVisitedStates;
100 public StateReducer(Config config, JPF jpf) {
101 debugMode = config.getBoolean("debug_state_transition", false);
102 stateReductionMode = config.getBoolean("activate_state_reduction", true);
104 out = new PrintWriter(System.out, true);
112 isBooleanCGFlipped = false;
113 vodGraphMap = new HashMap<>();
114 justVisitedStates = new HashSet<>();
115 prevChoiceValue = -1;
116 cgMap = new HashMap<>();
117 readWriteFieldsMap = new HashMap<>();
118 backtrackMap = new HashMap<>();
119 backtrackSet = new HashSet<>();
120 conflictPairMap = new HashMap<>();
121 unusedCG = new HashSet<>();
122 stateToEventMap = new HashMap<>();
123 prevVisitedStates = new HashSet<>();
124 currVisitedStates = new HashSet<>();
125 initializeStateReduction();
128 private void initializeStateReduction() {
129 if (stateReductionMode) {
134 choiceUpperBound = 0;
136 isInitialized = false;
137 isResetAfterAnalysis = false;
139 resetReadWriteAnalysis();
140 backtrackMap.clear();
141 backtrackSet.clear();
146 public void stateRestored(Search search) {
148 id = search.getStateId();
149 depth = search.getDepth();
150 transition = search.getTransition();
152 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
153 " and depth: " + depth + "\n");
157 //--- the ones we are interested in
159 public void searchStarted(Search search) {
161 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
165 private void resetReadWriteAnalysis() {
166 // Reset the following data structure when the choice counter reaches 0 again
167 conflictPairMap.clear();
168 readWriteFieldsMap.clear();
171 private IntChoiceFromSet setNewCG(IntChoiceFromSet icsCG) {
172 icsCG.setNewValues(choices);
174 // Use a modulo since choiceCounter is going to keep increasing
175 int choiceIndex = choiceCounter % choices.length;
176 icsCG.advance(choices[choiceIndex]);
177 if (choiceIndex == 0) {
178 resetReadWriteAnalysis();
183 private Integer[] copyChoices(Integer[] choicesToCopy) {
185 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
186 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
187 return copyOfChoices;
190 private void continueExecutingThisTrace(IntChoiceFromSet icsCG) {
191 // We repeat the same trace if a state match is not found yet
192 IntChoiceFromSet setCG = setNewCG(icsCG);
196 private void initializeChoiceGenerators(IntChoiceFromSet icsCG, Integer[] cgChoices) {
197 if (choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
198 // Update the choices of the first CG and add '-1'
199 if (choices == null) {
200 // Initialize backtrack set that stores all the explored backtrack lists
201 maxUpperBound = cgChoices.length;
202 // All the choices are always the same so we only need to update it once
203 // Get the choice array and final choice in the array
205 // Make a copy of choices as reference
206 refChoices = copyChoices(choices);
207 String firstChoiceListString = buildStringFromChoiceList(choices);
208 backtrackSet.add(firstChoiceListString);
210 IntChoiceFromSet setCG = setNewCG(icsCG);
211 cgMap.put(setCG, refChoices[choiceCounter]);
213 continueExecutingThisTrace(icsCG);
217 private void manageChoiceGeneratorsInSubsequentTraces(IntChoiceFromSet icsCG) {
218 // If this is the first iteration of the trace then set other CGs done
219 if (choiceCounter <= choiceUpperBound) {
222 // If this is the subsequent iterations of the trace then set up new CGs to continue the execution
223 continueExecutingThisTrace(icsCG);
228 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
229 if (stateReductionMode) {
230 // Initialize with necessary information from the CG
231 if (nextCG instanceof IntChoiceFromSet) {
232 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
233 // Check if CG has been initialized, otherwise initialize it
234 Integer[] cgChoices = icsCG.getAllChoices();
235 if (!isInitialized) {
236 // Get the upper bound from the last element of the choices
237 choiceUpperBound = cgChoices[cgChoices.length - 1];
238 isInitialized = true;
240 // Record the subsequent Integer CGs only until we hit the upper bound
241 if (!isResetAfterAnalysis) {
242 initializeChoiceGenerators(icsCG, cgChoices);
244 // Set new CGs to done so that the search algorithm explores the existing CGs
246 manageChoiceGeneratorsInSubsequentTraces(icsCG);
253 private void setDoneUnusedCG() {
254 // Set done every CG in the unused CG set
255 for (IntChoiceFromSet cg : unusedCG) {
261 private void resetAllCGs() {
262 // Extract the event numbers that have backtrack lists
263 Set<Integer> eventSet = backtrackMap.keySet();
264 // Return if there is no conflict at all (highly unlikely)
265 if (eventSet.isEmpty()) {
266 // Set every CG to done!
267 for (IntChoiceFromSet cg : cgMap.keySet()) {
272 // Reset every CG with the first backtrack lists
273 for (IntChoiceFromSet cg : cgMap.keySet()) {
274 int event = cgMap.get(cg);
275 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
276 if (choiceLists != null && choiceLists.peekFirst() != null) {
277 Integer[] choiceList = choiceLists.removeFirst();
278 // Deploy the new choice list for this CG
279 cg.setNewValues(choiceList);
289 // Detect cycles in the current execution/trace
290 // We terminate the execution iff:
291 // (1) the state has been visited in the current execution
292 // (2) the state has one or more cycles that involve all the events
293 // With simple approach we only need to check for a re-visited state.
294 // Basically, we have to check that we have executed all events between two occurrences of such state.
295 private boolean containsCyclesWithAllEvents(int stId) {
297 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
298 boolean containsCyclesWithAllEvts = false;
299 if (checkIfAllEventsInvolved(visitedEvents)) {
300 containsCyclesWithAllEvts = true;
303 return containsCyclesWithAllEvts;
306 private boolean checkIfAllEventsInvolved(HashSet<Integer> visitedEvents) {
308 // Check if this set contains all the event choices
309 // If not then this is not the terminating condition
310 for(int i=0; i<=choiceUpperBound; i++) {
311 if (!visitedEvents.contains(i)) {
318 private void saveVisitedStates() {
320 // Save all the visited states
321 prevVisitedStates.addAll(currVisitedStates);
322 currVisitedStates.clear();
325 private void updateChoicesForNewExecution(IntChoiceFromSet icsCG) {
326 if (choices == null || choices != icsCG.getAllChoices()) {
328 choices = icsCG.getAllChoices();
329 refChoices = copyChoices(choices);
330 // Reset a few things for the sub-graph
331 resetReadWriteAnalysis();
336 private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
337 // Traverse the sub-graphs
338 if (isResetAfterAnalysis) {
339 // Do this for every CG after finishing each backtrack list
340 // We try to update the CG with a backtrack list if the state has been visited multiple times
341 //if ((icsCG.getNextChoice() == -1 || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
342 //if ((!icsCG.hasMoreChoices() || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
343 if (choiceCounter > 1 && cgMap.containsKey(icsCG)) {
344 int event = cgMap.get(icsCG);
345 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
346 if (choiceLists != null && choiceLists.peekFirst() != null) {
347 Integer[] choiceList = choiceLists.removeFirst();
348 // Deploy the new choice list for this CG
349 icsCG.setNewValues(choiceList);
352 // Set done if this was the last backtrack list
359 // Update and reset the CG if needed (do this for the first time after the analysis)
360 // Start backtracking if this is a visited state and it is not a repeating state
362 isResetAfterAnalysis = true;
366 private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
367 // Check the next choice and if the value is not the same as the expected then force the expected value
368 int choiceIndex = (choiceCounter - 1) % refChoices.length;
369 if (choices[choiceIndex] != icsCG.getNextChoiceIndex()) {
370 int expectedChoice = refChoices[choiceIndex];
371 int currCGIndex = icsCG.getNextChoiceIndex();
372 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
373 icsCG.setChoice(currCGIndex, expectedChoice);
378 private boolean terminateCurrentExecution() {
379 // We need to check all the states that have just been visited
380 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
381 for(Integer stateId : justVisitedStates) {
382 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
390 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
392 if (stateReductionMode) {
393 // Check the boolean CG and if it is flipped, we are resetting the analysis
394 if (currentCG instanceof BooleanChoiceGenerator) {
395 if (!isBooleanCGFlipped) {
396 isBooleanCGFlipped = true;
398 initializeStateReduction();
401 // Check every choice generated and make sure that all the available choices
402 // are chosen first before repeating the same choice of value twice!
403 if (currentCG instanceof IntChoiceFromSet) {
404 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
405 // Update the current pointer to the current set of choices
406 updateChoicesForNewExecution(icsCG);
407 // Check if we have seen this state or this state contains cycles that involve all events
408 if (terminateCurrentExecution()) {
409 exploreNextBacktrackSets(icsCG);
411 justVisitedStates.clear();
412 // If we don't see a fair scheduling of events/choices then we have to enforce it
413 checkAndEnforceFairScheduling(icsCG);
414 // Update the VOD graph always with the latest
415 updateVODGraph(icsCG.getNextChoice());
420 private void updateVODGraph(int currChoiceValue) {
421 // Update the graph when we have the current choice value
422 HashSet<Integer> choiceSet;
423 if (vodGraphMap.containsKey(prevChoiceValue)) {
424 // If the key already exists, just retrieve it
425 choiceSet = vodGraphMap.get(prevChoiceValue);
427 // Create a new entry
428 choiceSet = new HashSet<>();
429 vodGraphMap.put(prevChoiceValue, choiceSet);
431 choiceSet.add(currChoiceValue);
432 prevChoiceValue = currChoiceValue;
435 private void mapStateToEvent(Search search, int stateId) {
436 // Insert state ID and event choice into the map
437 HashSet<Integer> eventSet;
438 if (stateToEventMap.containsKey(stateId)) {
439 eventSet = stateToEventMap.get(stateId);
441 eventSet = new HashSet<>();
442 stateToEventMap.put(stateId, eventSet);
444 eventSet.add(prevChoiceValue);
447 private void updateStateInfo(Search search) {
448 if (stateReductionMode) {
449 // Update the state variables
450 // Line 19 in the paper page 11 (see the heading note above)
451 int stateId = search.getStateId();
452 currVisitedStates.add(stateId);
453 mapStateToEvent(search, stateId);
454 justVisitedStates.add(stateId);
459 public void stateAdvanced(Search search) {
461 id = search.getStateId();
462 depth = search.getDepth();
463 transition = search.getTransition();
464 if (search.isNewState()) {
470 if (search.isEndState()) {
471 out.println("\n==> DEBUG: This is the last state!\n");
474 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
475 " which is " + detail + " Transition: " + transition + "\n");
477 updateStateInfo(search);
481 public void stateBacktracked(Search search) {
483 id = search.getStateId();
484 depth = search.getDepth();
485 transition = search.getTransition();
488 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
489 " and depth: " + depth + "\n");
491 updateStateInfo(search);
495 public void searchFinished(Search search) {
497 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
501 // This class compactly stores Read and Write field sets
502 // We store the field name and its object ID
503 // Sharing the same field means the same field name and object ID
504 private class ReadWriteSet {
505 private HashMap<String, Integer> readSet;
506 private HashMap<String, Integer> writeSet;
508 public ReadWriteSet() {
509 readSet = new HashMap<>();
510 writeSet = new HashMap<>();
513 public void addReadField(String field, int objectId) {
514 readSet.put(field, objectId);
517 public void addWriteField(String field, int objectId) {
518 writeSet.put(field, objectId);
521 public boolean readFieldExists(String field) {
522 return readSet.containsKey(field);
525 public boolean writeFieldExists(String field) {
526 return writeSet.containsKey(field);
529 public int readFieldObjectId(String field) {
530 return readSet.get(field);
533 public int writeFieldObjectId(String field) {
534 return writeSet.get(field);
538 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
539 // Do the analysis to get Read and Write accesses to fields
541 // We already have an entry
542 if (readWriteFieldsMap.containsKey(refChoices[currentChoice])) {
543 rwSet = readWriteFieldsMap.get(refChoices[currentChoice]);
544 } else { // We need to create a new entry
545 rwSet = new ReadWriteSet();
546 readWriteFieldsMap.put(refChoices[currentChoice], rwSet);
548 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
549 // Record the field in the map
550 if (executedInsn instanceof WriteInstruction) {
551 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
552 for (String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
553 if (fieldClass.startsWith(str)) {
557 rwSet.addWriteField(fieldClass, objectId);
558 } else if (executedInsn instanceof ReadInstruction) {
559 rwSet.addReadField(fieldClass, objectId);
563 private boolean recordConflictPair(int currentEvent, int eventNumber) {
564 HashSet<Integer> conflictSet;
565 if (!conflictPairMap.containsKey(currentEvent)) {
566 conflictSet = new HashSet<>();
567 conflictPairMap.put(currentEvent, conflictSet);
569 conflictSet = conflictPairMap.get(currentEvent);
571 // If this conflict has been recorded before, we return false because
572 // we don't want to service this backtrack point twice
573 if (conflictSet.contains(eventNumber)) {
576 // If it hasn't been recorded, then do otherwise
577 conflictSet.add(eventNumber);
581 private String buildStringFromChoiceList(Integer[] newChoiceList) {
583 // When we see a choice list shorter than the upper bound, e.g., [3,2] for choices 0,1,2, and 3,
584 // then we have to pad the beginning before we store it, because [3,2] actually means [0,1,3,2]
585 // First, calculate the difference between this choice list and the upper bound
586 // The actual list doesn't include '-1' at the end
587 int actualListLength = newChoiceList.length - 1;
588 int diff = maxUpperBound - actualListLength;
589 StringBuilder sb = new StringBuilder();
590 // Pad the beginning if necessary
591 for (int i = 0; i < diff; i++) {
594 // Then continue with the actual choice list
595 // We don't include the '-1' at the end
596 for (int i = 0; i < newChoiceList.length - 1; i++) {
597 sb.append(newChoiceList[i]);
599 return sb.toString();
602 private void checkAndAddBacktrackList(LinkedList<Integer[]> backtrackChoiceLists, Integer[] newChoiceList) {
604 String newChoiceListString = buildStringFromChoiceList(newChoiceList);
605 // Add only if we haven't seen this combination before
606 if (!backtrackSet.contains(newChoiceListString)) {
607 backtrackSet.add(newChoiceListString);
608 backtrackChoiceLists.addLast(newChoiceList);
612 private void createBacktrackChoiceList(int currentChoice, int conflictEventNumber) {
614 LinkedList<Integer[]> backtrackChoiceLists;
615 // Create a new list of choices for backtrack based on the current choice and conflicting event number
616 // If we have a conflict between 1 and 3, then we create the list {3, 1, 2, 4, 5} for backtrack
617 // The backtrack point is the CG for event number 1 and the list length is one less than the original list
618 // (originally of length 6) since we don't start from event number 0
619 if (!isResetAfterAnalysis) {
620 // Check if we have a list for this choice number
621 // If not we create a new one for it
622 if (!backtrackMap.containsKey(conflictEventNumber)) {
623 backtrackChoiceLists = new LinkedList<>();
624 backtrackMap.put(conflictEventNumber, backtrackChoiceLists);
626 backtrackChoiceLists = backtrackMap.get(conflictEventNumber);
628 int maxListLength = choiceUpperBound + 1;
629 int listLength = maxListLength - conflictEventNumber;
630 Integer[] newChoiceList = new Integer[listLength];
631 // Put the conflicting event numbers first and reverse the order
632 newChoiceList[0] = refChoices[currentChoice];
633 newChoiceList[1] = refChoices[conflictEventNumber];
634 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
635 for (int i = conflictEventNumber + 1, j = 2; j < listLength; i++) {
636 if (refChoices[i] != refChoices[currentChoice]) {
637 newChoiceList[j] = refChoices[i];
641 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
642 // The start index for the recursion is always 1 (from the main branch)
643 } else { // This is a sub-graph
644 // There is a case/bug that after a re-initialization, currCG is not yet initialized
645 if (currCG != null && cgMap.containsKey(currCG)) {
646 int backtrackListIndex = cgMap.get(currCG);
647 backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
648 int listLength = refChoices.length;
649 Integer[] newChoiceList = new Integer[listLength];
650 // Copy everything before the conflict number
651 for (int i = 0; i < conflictEventNumber; i++) {
652 newChoiceList[i] = refChoices[i];
654 // Put the conflicting events
655 newChoiceList[conflictEventNumber] = refChoices[currentChoice];
656 newChoiceList[conflictEventNumber + 1] = refChoices[conflictEventNumber];
658 for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
659 if (refChoices[i] != refChoices[currentChoice]) {
660 newChoiceList[j] = refChoices[i];
664 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
669 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
670 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
671 // Java and Groovy libraries
672 { "java", "org", "sun", "com", "gov", "groovy"};
673 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
674 // Groovy library created fields
675 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
677 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
678 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
679 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
680 private final static String[] EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
682 private boolean isFieldExcluded(String field) {
683 // Check against "starts-with" list
684 for(String str : EXCLUDED_FIELDS_STARTS_WITH_LIST) {
685 if (field.startsWith(str)) {
689 // Check against "ends-with" list
690 for(String str : EXCLUDED_FIELDS_ENDS_WITH_LIST) {
691 if (field.endsWith(str)) {
695 // Check against "contains" list
696 for(String str : EXCLUDED_FIELDS_CONTAINS_LIST) {
697 if (field.contains(str)) {
705 // This method checks whether a choice is reachable in the VOD graph from a reference choice
706 // This is a BFS search
707 private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
708 // Record visited choices as we search in the graph
709 HashSet<Integer> visitedChoice = new HashSet<>();
710 visitedChoice.add(referenceChoice);
711 LinkedList<Integer> nodesToVisit = new LinkedList<>();
712 // If the state doesn't advance as the threads/sub-programs are executed (basically there is no new state),
713 // there is a chance that the graph doesn't have new nodes---thus this check will return a null.
714 if (vodGraphMap.containsKey(referenceChoice)) {
715 nodesToVisit.addAll(vodGraphMap.get(referenceChoice));
716 while(!nodesToVisit.isEmpty()) {
717 int currChoice = nodesToVisit.getFirst();
718 if (currChoice == checkedChoice) {
721 if (visitedChoice.contains(currChoice)) {
722 // If there is a loop then we don't find it
725 // Continue searching
726 visitedChoice.add(currChoice);
727 HashSet<Integer> currChoiceNextNodes = vodGraphMap.get(currChoice);
728 if (currChoiceNextNodes != null) {
729 // Add only if there is a mapping for next nodes
730 for (Integer nextNode : currChoiceNextNodes) {
732 if (nextNode == currChoice) {
735 nodesToVisit.addLast(nextNode);
744 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
745 if (stateReductionMode) {
747 int currentChoice = (choiceCounter % refChoices.length) - 1;
748 if (currentChoice < 0) {
749 // We do not compute the conflicts for the choice '-1'
752 // Record accesses from executed instructions
753 if (executedInsn instanceof JVMFieldInstruction) {
754 // Analyze only after being initialized
755 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
756 // We don't care about libraries
757 if (!isFieldExcluded(fieldClass)) {
758 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
761 // Analyze conflicts from next instructions
762 if (nextInsn instanceof JVMFieldInstruction) {
763 // The constructor is only called once when the object is initialized
764 // It does not have shared access with other objects
765 MethodInfo mi = nextInsn.getMethodInfo();
766 if (!mi.getName().equals("<init>")) {
767 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
768 // We don't care about libraries
769 if (!isFieldExcluded(fieldClass)) {
770 // Check for conflict (go backward from currentChoice and get the first conflict)
771 // If the current event has conflicts with multiple events, then these will be detected
772 // one by one as this recursively checks backward when backtrack set is revisited and executed.
773 for (int eventNumber = currentChoice - 1; eventNumber >= 0; eventNumber--) {
774 // Skip if this event number does not have any Read/Write set
775 if (!readWriteFieldsMap.containsKey(refChoices[eventNumber])) {
778 ReadWriteSet rwSet = readWriteFieldsMap.get(refChoices[eventNumber]);
779 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
780 // 1) Check for conflicts with Write fields for both Read and Write instructions
781 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
782 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
783 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
784 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
785 // We do not record and service the same backtrack pair/point twice!
786 // If it has been serviced before, we just skip this
787 if (recordConflictPair(currentChoice, eventNumber)) {
788 // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
789 if (vm.isNewState() || isReachableInVODGraph(refChoices[currentChoice], refChoices[currentChoice-1])) {
790 createBacktrackChoiceList(currentChoice, eventNumber);
791 // Break if a conflict is found!