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 IntChoiceFromSet currCG;
63 private int choiceCounter;
64 private Integer choiceUpperBound;
65 private Integer maxUpperBound;
66 private boolean isInitialized;
67 private boolean isResetAfterAnalysis;
68 private boolean isBooleanCGFlipped;
69 private HashMap<IntChoiceFromSet, Integer> cgMap;
70 // Record the mapping between event number and field accesses (Read and Write)
71 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
72 // The following is the backtrack map (set) that stores all the backtrack information
73 // e.g., event number 1 can have two backtrack sequences: {3,1,2,4,...} and {2,1,3,4,...}
74 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap;
75 // Stores explored backtrack lists in the form of HashSet of Strings
76 private HashSet<String> backtrackSet;
77 private HashMap<Integer, HashSet<Integer>> conflictPairMap;
79 // Map that represents graph G
80 // (i.e., visible operation dependency graph (VOD Graph)
81 private HashMap<Integer, HashSet<Integer>> vodGraphMap;
82 // Set that represents hash table H
83 // (i.e., hash table that records encountered states)
84 // VOD graph is updated when the state has not yet been seen
87 // Previous choice number
88 private int prevChoiceValue;
89 // HashSet that stores references to unused CGs
90 private HashSet<IntChoiceFromSet> unusedCG;
92 // Reference to the state graph in the ConflictTracker class
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<>();
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 // TODO: We are assuming that the StateReducer is always used together with the ConflictTracker
123 stateGraph = ConflictTracker.nodes;
124 stateToEventMap = new HashMap<>();
125 prevVisitedStates = new HashSet<>();
126 currVisitedStates = new HashSet<>();
127 initializeStateReduction();
130 private void initializeStateReduction() {
131 if (stateReductionMode) {
135 choiceUpperBound = 0;
137 isInitialized = false;
138 isResetAfterAnalysis = false;
140 readWriteFieldsMap.clear();
141 backtrackMap.clear();
142 backtrackSet.clear();
143 conflictPairMap.clear();
148 public void stateRestored(Search search) {
150 id = search.getStateId();
151 depth = search.getDepth();
152 transition = search.getTransition();
154 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
155 " and depth: " + depth + "\n");
159 //--- the ones we are interested in
161 public void searchStarted(Search search) {
163 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
167 private IntChoiceFromSet setNewCG(IntChoiceFromSet icsCG) {
168 icsCG.setNewValues(choices);
170 // Use a modulo since choiceCounter is going to keep increasing
171 int choiceIndex = choiceCounter % (choices.length - 1);
172 icsCG.advance(choices[choiceIndex]);
176 private void initializeChoiceGenerators(IntChoiceFromSet icsCG, Integer[] cgChoices) {
177 if (choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
178 // Update the choices of the first CG and add '-1'
179 if (choices == null) {
180 // Initialize backtrack set that stores all the explored backtrack lists
181 maxUpperBound = cgChoices.length;
182 // All the choices are always the same so we only need to update it once
183 choices = new Integer[cgChoices.length + 1];
184 System.arraycopy(cgChoices, 0, choices, 0, cgChoices.length);
185 choices[choices.length - 1] = -1;
186 String firstChoiceListString = buildStringFromChoiceList(choices);
187 backtrackSet.add(firstChoiceListString);
189 IntChoiceFromSet setCG = setNewCG(icsCG);
190 cgMap.put(setCG, choices[choiceCounter]);
192 // We repeat the same trace if a state match is not found yet
193 IntChoiceFromSet setCG = setNewCG(icsCG);
196 //choiceCounter = choiceCounter < choiceUpperBound ? choiceCounter + 1 : 0;
201 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
202 if (stateReductionMode) {
203 // Initialize with necessary information from the CG
204 if (nextCG instanceof IntChoiceFromSet) {
205 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
206 // Check if CG has been initialized, otherwise initialize it
207 Integer[] cgChoices = icsCG.getAllChoices();
208 if (!isInitialized) {
209 // Get the upper bound from the last element of the choices
210 choiceUpperBound = cgChoices[cgChoices.length - 1];
211 isInitialized = true;
213 // Record the subsequent Integer CGs only until we hit the upper bound
214 if (!isResetAfterAnalysis) {
215 initializeChoiceGenerators(icsCG, cgChoices);
217 // Set new CGs to done so that the search algorithm explores the existing CGs
224 private void resetAllCGs() {
225 // Extract the event numbers that have backtrack lists
226 Set<Integer> eventSet = backtrackMap.keySet();
227 // Return if there is no conflict at all (highly unlikely)
228 if (eventSet.isEmpty()) {
229 // Set every CG to done!
230 for (IntChoiceFromSet cg : cgMap.keySet()) {
235 // Reset every CG with the first backtrack lists
236 for (IntChoiceFromSet cg : cgMap.keySet()) {
237 int event = cgMap.get(cg);
238 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
239 if (choiceLists != null && choiceLists.peekFirst() != null) {
240 Integer[] choiceList = choiceLists.removeFirst();
241 // Deploy the new choice list for this CG
242 cg.setNewValues(choiceList);
248 // Set done every CG in the unused CG set
249 for (IntChoiceFromSet cg : unusedCG) {
256 // Detect cycles in the current execution/trace
257 // We terminate the execution iff:
258 // (1) the state has been visited in the current execution
259 // (2) the state has one or more cycles that involve all the events
260 // With simple approach we only need to check for a re-visited state.
261 // Basically, we have to check that we have executed all events between two occurrences of such state.
262 private boolean containsCyclesWithAllEvents(int stId) {
264 HashSet<ConflictTracker.Node> visitingStates = new HashSet<>();
265 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
266 boolean containsCyclesWithAllEvts = false;
267 if (checkIfAllEventsInvolved(visitedEvents)) {
268 containsCyclesWithAllEvts = true;
271 return containsCyclesWithAllEvts;
274 // TODO: The following is a full-blown graph traversal that we can do if we need to in the future
275 // Detect cycles in the current execution/trace
276 // We terminate the execution iff:
277 // (1) the state has been visited in the current execution
278 // (2) the state has one or more cycles that involve all the events
279 // private boolean containsCyclesWithAllEvents(int stId) {
281 // HashSet<ConflictTracker.Node> visitingStates = new HashSet<>();
282 // HashSet<Integer> visitedEvents = new HashSet<>();
283 // boolean containsCyclesWithAllEvts = false;
284 // ConflictTracker.Node currNode = stateGraph.get(stId);
285 // dfsFindCycles(currNode, visitingStates, visitedEvents, new HashSet<>());
286 // if (checkIfAllEventsInvolved(visitedEvents)) {
287 // containsCyclesWithAllEvts = true;
290 // return containsCyclesWithAllEvts;
293 // private void dfsFindCycles(ConflictTracker.Node currNode, HashSet<ConflictTracker.Node> visitingStates,
294 // HashSet<Integer> visitedEvents, HashSet<Integer> visitingEvents) {
296 // // Stop when there is a cycle and record all the events
297 // if (visitingStates.contains(currNode)) {
298 // visitedEvents.addAll(visitingEvents);
300 // visitingStates.add(currNode);
301 // for(ConflictTracker.Edge edge : currNode.getOutEdges()) {
302 // visitingEvents.add(edge.getEventNumber());
303 // dfsFindCycles(edge.getDst(), visitingStates, visitedEvents, visitingEvents);
304 // visitingEvents.remove(edge.getEventNumber());
306 // visitingStates.remove(currNode);
310 private boolean checkIfAllEventsInvolved(HashSet<Integer> visitedEvents) {
312 // Check if this set contains all the event choices
313 // If not then this is not the terminating condition
314 for(int i=0; i<=choiceUpperBound; i++) {
315 if (!visitedEvents.contains(i)) {
322 private void saveVisitedStates() {
324 // Save all the visited states
325 prevVisitedStates.addAll(currVisitedStates);
326 currVisitedStates.clear();
329 private void updateChoices(IntChoiceFromSet icsCG) {
330 if (choices == null || choices != icsCG.getAllChoices()) {
332 choices = icsCG.getAllChoices();
333 // Reset a few things for the sub-graph
334 conflictPairMap.clear();
335 readWriteFieldsMap.clear();
340 private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
341 // Traverse the sub-graphs
342 if (isResetAfterAnalysis) {
343 // Advance choice counter for sub-graphs
345 // Do this for every CG after finishing each backtrack list
346 // We try to update the CG with a backtrack list if the state has been visited multiple times
347 if ((icsCG.getNextChoice() == -1 || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
348 int event = cgMap.get(icsCG);
349 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
350 if (choiceLists != null && choiceLists.peekFirst() != null) {
351 Integer[] choiceList = choiceLists.removeFirst();
352 // Deploy the new choice list for this CG
353 icsCG.setNewValues(choiceList);
356 // Set done if this was the last backtrack list
362 // Update and reset the CG if needed (do this for the first time after the analysis)
363 // Start backtracking if this is a visited state and it is not a repeating state
365 isResetAfterAnalysis = true;
370 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
372 if (stateReductionMode) {
373 // Check the boolean CG and if it is flipped, we are resetting the analysis
374 if (currentCG instanceof BooleanChoiceGenerator) {
375 if (!isBooleanCGFlipped) {
376 isBooleanCGFlipped = true;
378 initializeStateReduction();
381 // Check every choice generated and make sure that all the available choices
382 // are chosen first before repeating the same choice of value twice!
383 if (currentCG instanceof IntChoiceFromSet) {
384 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
385 // Update the current pointer to the current set of choices
386 updateChoices(icsCG);
387 // Check if we have seen this state or this state contains cycles that involve all events
388 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
389 exploreNextBacktrackSets(icsCG);
391 // Update the VOD graph always with the latest
392 updateVODGraph(icsCG.getNextChoice());
397 private void updateVODGraph(int currChoiceValue) {
398 // Update the graph when we have the current choice value
399 updateVODGraph(prevChoiceValue, currChoiceValue);
400 prevChoiceValue = currChoiceValue;
403 private void updateVODGraph(int prevChoice, int currChoice) {
405 HashSet<Integer> choiceSet;
406 if (vodGraphMap.containsKey(prevChoice)) {
407 // If the key already exists, just retrieve it
408 choiceSet = vodGraphMap.get(prevChoice);
410 // Create a new entry
411 choiceSet = new HashSet<>();
412 vodGraphMap.put(prevChoice, choiceSet);
414 choiceSet.add(currChoice);
417 private void mapStateToEvent(Search search) {
418 // Insert state ID and event choice into the map
419 HashSet<Integer> eventSet;
420 if (stateToEventMap.containsKey(stateId)) {
421 eventSet = stateToEventMap.get(stateId);
423 eventSet = new HashSet<>();
424 stateToEventMap.put(stateId, eventSet);
426 eventSet.add(prevChoiceValue);
429 private void updateStateInfo(Search search) {
430 if (stateReductionMode) {
431 // Update the state variables
432 // Line 19 in the paper page 11 (see the heading note above)
433 stateId = search.getStateId();
434 currVisitedStates.add(stateId);
435 mapStateToEvent(search);
440 public void stateAdvanced(Search search) {
442 id = search.getStateId();
443 depth = search.getDepth();
444 transition = search.getTransition();
445 if (search.isNewState()) {
451 if (search.isEndState()) {
452 out.println("\n==> DEBUG: This is the last state!\n");
455 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
456 " which is " + detail + " Transition: " + transition + "\n");
458 updateStateInfo(search);
462 public void stateBacktracked(Search search) {
464 id = search.getStateId();
465 depth = search.getDepth();
466 transition = search.getTransition();
469 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
470 " and depth: " + depth + "\n");
472 updateStateInfo(search);
476 public void searchFinished(Search search) {
478 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
482 // This class compactly stores Read and Write field sets
483 // We store the field name and its object ID
484 // Sharing the same field means the same field name and object ID
485 private class ReadWriteSet {
486 private HashMap<String, Integer> readSet;
487 private HashMap<String, Integer> writeSet;
489 public ReadWriteSet() {
490 readSet = new HashMap<>();
491 writeSet = new HashMap<>();
494 public void addReadField(String field, int objectId) {
495 readSet.put(field, objectId);
498 public void addWriteField(String field, int objectId) {
499 writeSet.put(field, objectId);
502 public boolean readFieldExists(String field) {
503 return readSet.containsKey(field);
506 public boolean writeFieldExists(String field) {
507 return writeSet.containsKey(field);
510 public int readFieldObjectId(String field) {
511 return readSet.get(field);
514 public int writeFieldObjectId(String field) {
515 return writeSet.get(field);
519 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
520 // Do the analysis to get Read and Write accesses to fields
522 // We already have an entry
523 if (readWriteFieldsMap.containsKey(choices[currentChoice])) {
524 rwSet = readWriteFieldsMap.get(choices[currentChoice]);
525 } else { // We need to create a new entry
526 rwSet = new ReadWriteSet();
527 readWriteFieldsMap.put(choices[currentChoice], rwSet);
529 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
530 // Record the field in the map
531 if (executedInsn instanceof WriteInstruction) {
532 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
533 for (String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
534 if (fieldClass.startsWith(str)) {
538 rwSet.addWriteField(fieldClass, objectId);
539 } else if (executedInsn instanceof ReadInstruction) {
540 rwSet.addReadField(fieldClass, objectId);
544 private boolean recordConflictPair(int currentEvent, int eventNumber) {
545 HashSet<Integer> conflictSet;
546 if (!conflictPairMap.containsKey(currentEvent)) {
547 conflictSet = new HashSet<>();
548 conflictPairMap.put(currentEvent, conflictSet);
550 conflictSet = conflictPairMap.get(currentEvent);
552 // If this conflict has been recorded before, we return false because
553 // we don't want to service this backtrack point twice
554 if (conflictSet.contains(eventNumber)) {
557 // If it hasn't been recorded, then do otherwise
558 conflictSet.add(eventNumber);
562 private String buildStringFromChoiceList(Integer[] newChoiceList) {
564 // When we see a choice list shorter than the upper bound, e.g., [3,2] for choices 0,1,2, and 3,
565 // then we have to pad the beginning before we store it, because [3,2] actually means [0,1,3,2]
566 // First, calculate the difference between this choice list and the upper bound
567 // The actual list doesn't include '-1' at the end
568 int actualListLength = newChoiceList.length - 1;
569 int diff = maxUpperBound - actualListLength;
570 StringBuilder sb = new StringBuilder();
571 // Pad the beginning if necessary
572 for (int i = 0; i < diff; i++) {
575 // Then continue with the actual choice list
576 // We don't include the '-1' at the end
577 for (int i = 0; i < newChoiceList.length - 1; i++) {
578 sb.append(newChoiceList[i]);
580 return sb.toString();
583 private void checkAndAddBacktrackList(LinkedList<Integer[]> backtrackChoiceLists, Integer[] newChoiceList) {
585 String newChoiceListString = buildStringFromChoiceList(newChoiceList);
586 // Add only if we haven't seen this combination before
587 if (!backtrackSet.contains(newChoiceListString)) {
588 backtrackSet.add(newChoiceListString);
589 backtrackChoiceLists.addLast(newChoiceList);
593 private void createBacktrackChoiceList(int currentChoice, int conflictEventNumber) {
595 LinkedList<Integer[]> backtrackChoiceLists;
596 // Create a new list of choices for backtrack based on the current choice and conflicting event number
597 // If we have a conflict between 1 and 3, then we create the list {3, 1, 2, 4, 5} for backtrack
598 // The backtrack point is the CG for event number 1 and the list length is one less than the original list
599 // (originally of length 6) since we don't start from event number 0
600 if (!isResetAfterAnalysis) {
601 // Check if we have a list for this choice number
602 // If not we create a new one for it
603 if (!backtrackMap.containsKey(conflictEventNumber)) {
604 backtrackChoiceLists = new LinkedList<>();
605 backtrackMap.put(conflictEventNumber, backtrackChoiceLists);
607 backtrackChoiceLists = backtrackMap.get(conflictEventNumber);
609 int maxListLength = choiceUpperBound + 1;
610 int listLength = maxListLength - conflictEventNumber;
611 Integer[] newChoiceList = new Integer[listLength + 1];
612 // Put the conflicting event numbers first and reverse the order
613 newChoiceList[0] = choices[currentChoice];
614 newChoiceList[1] = choices[conflictEventNumber];
615 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
616 for (int i = conflictEventNumber + 1, j = 2; j < listLength; i++) {
617 if (choices[i] != choices[currentChoice]) {
618 newChoiceList[j] = choices[i];
622 // Set the last element to '-1' as the end of the sequence
623 newChoiceList[newChoiceList.length - 1] = -1;
624 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
625 // The start index for the recursion is always 1 (from the main branch)
626 } else { // This is a sub-graph
627 // There is a case/bug that after a re-initialization, currCG is not yet initialized
628 if (currCG != null && cgMap.containsKey(currCG)) {
629 int backtrackListIndex = cgMap.get(currCG);
630 backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
631 int listLength = choices.length;
632 Integer[] newChoiceList = new Integer[listLength];
633 // Copy everything before the conflict number
634 for (int i = 0; i < conflictEventNumber; i++) {
635 newChoiceList[i] = choices[i];
637 // Put the conflicting events
638 newChoiceList[conflictEventNumber] = choices[currentChoice];
639 newChoiceList[conflictEventNumber + 1] = choices[conflictEventNumber];
641 for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
642 if (choices[i] != choices[currentChoice]) {
643 newChoiceList[j] = choices[i];
647 // Set the last element to '-1' as the end of the sequence
648 newChoiceList[newChoiceList.length - 1] = -1;
649 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
654 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
655 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
656 // Java and Groovy libraries
657 { "java", "org", "sun", "com", "gov", "groovy"};
658 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
659 // Groovy library created fields
660 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
662 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
663 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
664 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
665 private final static String[] EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
667 private boolean isFieldExcluded(String field) {
668 // Check against "starts-with" list
669 for(String str : EXCLUDED_FIELDS_STARTS_WITH_LIST) {
670 if (field.startsWith(str)) {
674 // Check against "ends-with" list
675 for(String str : EXCLUDED_FIELDS_ENDS_WITH_LIST) {
676 if (field.endsWith(str)) {
680 // Check against "contains" list
681 for(String str : EXCLUDED_FIELDS_CONTAINS_LIST) {
682 if (field.contains(str)) {
690 // This method checks whether a choice is reachable in the VOD graph from a reference choice
691 // This is a BFS search
692 private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
693 // Record visited choices as we search in the graph
694 HashSet<Integer> visitedChoice = new HashSet<>();
695 visitedChoice.add(referenceChoice);
696 LinkedList<Integer> nodesToVisit = new LinkedList<>();
697 // If the state doesn't advance as the threads/sub-programs are executed (basically there is no new state),
698 // there is a chance that the graph doesn't have new nodes---thus this check will return a null.
699 if (vodGraphMap.containsKey(referenceChoice)) {
700 nodesToVisit.addAll(vodGraphMap.get(referenceChoice));
701 while(!nodesToVisit.isEmpty()) {
702 int currChoice = nodesToVisit.getFirst();
703 if (currChoice == checkedChoice) {
706 if (visitedChoice.contains(currChoice)) {
707 // If there is a loop then we don't find it
710 // Continue searching
711 visitedChoice.add(currChoice);
712 HashSet<Integer> currChoiceNextNodes = vodGraphMap.get(currChoice);
713 if (currChoiceNextNodes != null) {
714 // Add only if there is a mapping for next nodes
715 for (Integer nextNode : currChoiceNextNodes) {
717 if (nextNode == currChoice) {
720 nodesToVisit.addLast(nextNode);
729 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
730 if (stateReductionMode) {
732 int currentChoice = (choiceCounter % (choices.length - 1)) - 1;
733 if (currentChoice < 0) {
734 // We do not compute the conflicts for the choice '-1'
737 // Record accesses from executed instructions
738 if (executedInsn instanceof JVMFieldInstruction) {
739 // Analyze only after being initialized
740 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
741 // We don't care about libraries
742 if (!isFieldExcluded(fieldClass)) {
743 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
746 // Analyze conflicts from next instructions
747 if (nextInsn instanceof JVMFieldInstruction) {
748 // The constructor is only called once when the object is initialized
749 // It does not have shared access with other objects
750 MethodInfo mi = nextInsn.getMethodInfo();
751 if (!mi.getName().equals("<init>")) {
752 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
753 // We don't care about libraries
754 if (!isFieldExcluded(fieldClass)) {
755 // Check for conflict (go backward from currentChoice and get the first conflict)
756 // If the current event has conflicts with multiple events, then these will be detected
757 // one by one as this recursively checks backward when backtrack set is revisited and executed.
758 for (int eventNumber = currentChoice - 1; eventNumber >= 0; eventNumber--) {
759 // Skip if this event number does not have any Read/Write set
760 if (!readWriteFieldsMap.containsKey(choices[eventNumber])) {
763 ReadWriteSet rwSet = readWriteFieldsMap.get(choices[eventNumber]);
764 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
765 // 1) Check for conflicts with Write fields for both Read and Write instructions
766 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
767 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
768 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
769 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
770 // We do not record and service the same backtrack pair/point twice!
771 // If it has been serviced before, we just skip this
772 if (recordConflictPair(currentChoice, eventNumber)) {
773 // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
774 if (vm.isNewState() ||
775 (!vm.isNewState() && isReachableInVODGraph(choices[currentChoice], choices[currentChoice-1]))) {
776 createBacktrackChoiceList(currentChoice, eventNumber);
777 // Break if a conflict is found!