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 initializeChoiceGenerators(IntChoiceFromSet icsCG, Integer[] cgChoices) {
191 if (choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
192 // Update the choices of the first CG and add '-1'
193 if (choices == null) {
194 // Initialize backtrack set that stores all the explored backtrack lists
195 maxUpperBound = cgChoices.length;
196 // All the choices are always the same so we only need to update it once
197 // Get the choice array and final choice in the array
199 // Make a copy of choices as reference
200 refChoices = copyChoices(choices);
201 String firstChoiceListString = buildStringFromChoiceList(choices);
202 backtrackSet.add(firstChoiceListString);
204 IntChoiceFromSet setCG = setNewCG(icsCG);
205 cgMap.put(setCG, refChoices[choiceCounter]);
207 // We repeat the same trace if a state match is not found yet
208 IntChoiceFromSet setCG = setNewCG(icsCG);
215 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
216 if (stateReductionMode) {
217 // Initialize with necessary information from the CG
218 if (nextCG instanceof IntChoiceFromSet) {
219 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
220 // Check if CG has been initialized, otherwise initialize it
221 Integer[] cgChoices = icsCG.getAllChoices();
222 if (!isInitialized) {
223 // Get the upper bound from the last element of the choices
224 choiceUpperBound = cgChoices[cgChoices.length - 1];
225 isInitialized = true;
227 // Record the subsequent Integer CGs only until we hit the upper bound
228 if (!isResetAfterAnalysis) {
229 initializeChoiceGenerators(icsCG, cgChoices);
231 // Set new CGs to done so that the search algorithm explores the existing CGs
238 private void setDoneUnusedCG() {
239 // Set done every CG in the unused CG set
240 for (IntChoiceFromSet cg : unusedCG) {
246 private void resetAllCGs() {
247 // Extract the event numbers that have backtrack lists
248 Set<Integer> eventSet = backtrackMap.keySet();
249 // Return if there is no conflict at all (highly unlikely)
250 if (eventSet.isEmpty()) {
251 // Set every CG to done!
252 for (IntChoiceFromSet cg : cgMap.keySet()) {
257 // Reset every CG with the first backtrack lists
258 for (IntChoiceFromSet cg : cgMap.keySet()) {
259 int event = cgMap.get(cg);
260 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
261 if (choiceLists != null && choiceLists.peekFirst() != null) {
262 Integer[] choiceList = choiceLists.removeFirst();
263 // Deploy the new choice list for this CG
264 cg.setNewValues(choiceList);
274 // Detect cycles in the current execution/trace
275 // We terminate the execution iff:
276 // (1) the state has been visited in the current execution
277 // (2) the state has one or more cycles that involve all the events
278 // With simple approach we only need to check for a re-visited state.
279 // Basically, we have to check that we have executed all events between two occurrences of such state.
280 private boolean containsCyclesWithAllEvents(int stId) {
282 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
283 boolean containsCyclesWithAllEvts = false;
284 if (checkIfAllEventsInvolved(visitedEvents)) {
285 containsCyclesWithAllEvts = true;
288 return containsCyclesWithAllEvts;
291 private boolean checkIfAllEventsInvolved(HashSet<Integer> visitedEvents) {
293 // Check if this set contains all the event choices
294 // If not then this is not the terminating condition
295 for(int i=0; i<=choiceUpperBound; i++) {
296 if (!visitedEvents.contains(i)) {
303 private void saveVisitedStates() {
305 // Save all the visited states
306 prevVisitedStates.addAll(currVisitedStates);
307 currVisitedStates.clear();
310 private void updateChoicesForNewExecution(IntChoiceFromSet icsCG) {
311 if (choices == null || choices != icsCG.getAllChoices()) {
313 choices = icsCG.getAllChoices();
314 refChoices = copyChoices(choices);
315 // Reset a few things for the sub-graph
316 resetReadWriteAnalysis();
321 private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
322 // Traverse the sub-graphs
323 if (isResetAfterAnalysis) {
324 // Advance choice counter for sub-graphs
326 // Do this for every CG after finishing each backtrack list
327 // We try to update the CG with a backtrack list if the state has been visited multiple times
328 //if ((icsCG.getNextChoice() == -1 || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
329 if ((!icsCG.hasMoreChoices() || choiceCounter > 1) && cgMap.containsKey(icsCG)) {
330 int event = cgMap.get(icsCG);
331 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
332 if (choiceLists != null && choiceLists.peekFirst() != null) {
333 Integer[] choiceList = choiceLists.removeFirst();
334 // Deploy the new choice list for this CG
335 icsCG.setNewValues(choiceList);
338 // Set done if this was the last backtrack list
344 // Update and reset the CG if needed (do this for the first time after the analysis)
345 // Start backtracking if this is a visited state and it is not a repeating state
347 isResetAfterAnalysis = true;
351 private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
352 // Check the next choice and if the value is not the same as the expected then force the expected value
353 int choiceIndex = (choiceCounter - 1) % refChoices.length;
354 if (choices[choiceIndex] != icsCG.getNextChoiceIndex()) {
355 int expectedChoice = refChoices[choiceIndex];
356 int currCGIndex = icsCG.getNextChoiceIndex();
357 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
358 icsCG.setChoice(currCGIndex, expectedChoice);
363 private boolean terminateCurrentExecution() {
364 // We need to check all the states that have just been visited
365 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
366 for(Integer stateId : justVisitedStates) {
367 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
375 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
377 if (stateReductionMode) {
378 // Check the boolean CG and if it is flipped, we are resetting the analysis
379 if (currentCG instanceof BooleanChoiceGenerator) {
380 if (!isBooleanCGFlipped) {
381 isBooleanCGFlipped = true;
383 initializeStateReduction();
386 // Check every choice generated and make sure that all the available choices
387 // are chosen first before repeating the same choice of value twice!
388 if (currentCG instanceof IntChoiceFromSet) {
389 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
390 // Update the current pointer to the current set of choices
391 updateChoicesForNewExecution(icsCG);
392 // Check if we have seen this state or this state contains cycles that involve all events
393 if (terminateCurrentExecution()) {
394 exploreNextBacktrackSets(icsCG);
396 justVisitedStates.clear();
397 // If we don't see a fair scheduling of events/choices then we have to enforce it
398 checkAndEnforceFairScheduling(icsCG);
399 // Update the VOD graph always with the latest
400 updateVODGraph(icsCG.getNextChoice());
405 private void updateVODGraph(int currChoiceValue) {
406 // Update the graph when we have the current choice value
407 HashSet<Integer> choiceSet;
408 if (vodGraphMap.containsKey(prevChoiceValue)) {
409 // If the key already exists, just retrieve it
410 choiceSet = vodGraphMap.get(prevChoiceValue);
412 // Create a new entry
413 choiceSet = new HashSet<>();
414 vodGraphMap.put(prevChoiceValue, choiceSet);
416 choiceSet.add(currChoiceValue);
417 prevChoiceValue = currChoiceValue;
420 private void mapStateToEvent(Search search, int stateId) {
421 // Insert state ID and event choice into the map
422 HashSet<Integer> eventSet;
423 if (stateToEventMap.containsKey(stateId)) {
424 eventSet = stateToEventMap.get(stateId);
426 eventSet = new HashSet<>();
427 stateToEventMap.put(stateId, eventSet);
429 eventSet.add(prevChoiceValue);
432 private void updateStateInfo(Search search) {
433 if (stateReductionMode) {
434 // Update the state variables
435 // Line 19 in the paper page 11 (see the heading note above)
436 int stateId = search.getStateId();
437 currVisitedStates.add(stateId);
438 mapStateToEvent(search, stateId);
439 justVisitedStates.add(stateId);
444 public void stateAdvanced(Search search) {
446 id = search.getStateId();
447 depth = search.getDepth();
448 transition = search.getTransition();
449 if (search.isNewState()) {
455 if (search.isEndState()) {
456 out.println("\n==> DEBUG: This is the last state!\n");
459 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
460 " which is " + detail + " Transition: " + transition + "\n");
462 updateStateInfo(search);
466 public void stateBacktracked(Search search) {
468 id = search.getStateId();
469 depth = search.getDepth();
470 transition = search.getTransition();
473 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
474 " and depth: " + depth + "\n");
476 updateStateInfo(search);
480 public void searchFinished(Search search) {
482 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
486 // This class compactly stores Read and Write field sets
487 // We store the field name and its object ID
488 // Sharing the same field means the same field name and object ID
489 private class ReadWriteSet {
490 private HashMap<String, Integer> readSet;
491 private HashMap<String, Integer> writeSet;
493 public ReadWriteSet() {
494 readSet = new HashMap<>();
495 writeSet = new HashMap<>();
498 public void addReadField(String field, int objectId) {
499 readSet.put(field, objectId);
502 public void addWriteField(String field, int objectId) {
503 writeSet.put(field, objectId);
506 public boolean readFieldExists(String field) {
507 return readSet.containsKey(field);
510 public boolean writeFieldExists(String field) {
511 return writeSet.containsKey(field);
514 public int readFieldObjectId(String field) {
515 return readSet.get(field);
518 public int writeFieldObjectId(String field) {
519 return writeSet.get(field);
523 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
524 // Do the analysis to get Read and Write accesses to fields
526 // We already have an entry
527 if (readWriteFieldsMap.containsKey(refChoices[currentChoice])) {
528 rwSet = readWriteFieldsMap.get(refChoices[currentChoice]);
529 } else { // We need to create a new entry
530 rwSet = new ReadWriteSet();
531 readWriteFieldsMap.put(refChoices[currentChoice], rwSet);
533 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
534 // Record the field in the map
535 if (executedInsn instanceof WriteInstruction) {
536 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
537 for (String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
538 if (fieldClass.startsWith(str)) {
542 rwSet.addWriteField(fieldClass, objectId);
543 } else if (executedInsn instanceof ReadInstruction) {
544 rwSet.addReadField(fieldClass, objectId);
548 private boolean recordConflictPair(int currentEvent, int eventNumber) {
549 HashSet<Integer> conflictSet;
550 if (!conflictPairMap.containsKey(currentEvent)) {
551 conflictSet = new HashSet<>();
552 conflictPairMap.put(currentEvent, conflictSet);
554 conflictSet = conflictPairMap.get(currentEvent);
556 // If this conflict has been recorded before, we return false because
557 // we don't want to service this backtrack point twice
558 if (conflictSet.contains(eventNumber)) {
561 // If it hasn't been recorded, then do otherwise
562 conflictSet.add(eventNumber);
566 private String buildStringFromChoiceList(Integer[] newChoiceList) {
568 // When we see a choice list shorter than the upper bound, e.g., [3,2] for choices 0,1,2, and 3,
569 // then we have to pad the beginning before we store it, because [3,2] actually means [0,1,3,2]
570 // First, calculate the difference between this choice list and the upper bound
571 // The actual list doesn't include '-1' at the end
572 int actualListLength = newChoiceList.length - 1;
573 int diff = maxUpperBound - actualListLength;
574 StringBuilder sb = new StringBuilder();
575 // Pad the beginning if necessary
576 for (int i = 0; i < diff; i++) {
579 // Then continue with the actual choice list
580 // We don't include the '-1' at the end
581 for (int i = 0; i < newChoiceList.length - 1; i++) {
582 sb.append(newChoiceList[i]);
584 return sb.toString();
587 private void checkAndAddBacktrackList(LinkedList<Integer[]> backtrackChoiceLists, Integer[] newChoiceList) {
589 String newChoiceListString = buildStringFromChoiceList(newChoiceList);
590 // Add only if we haven't seen this combination before
591 if (!backtrackSet.contains(newChoiceListString)) {
592 backtrackSet.add(newChoiceListString);
593 backtrackChoiceLists.addLast(newChoiceList);
597 private void createBacktrackChoiceList(int currentChoice, int conflictEventNumber) {
599 LinkedList<Integer[]> backtrackChoiceLists;
600 // Create a new list of choices for backtrack based on the current choice and conflicting event number
601 // If we have a conflict between 1 and 3, then we create the list {3, 1, 2, 4, 5} for backtrack
602 // The backtrack point is the CG for event number 1 and the list length is one less than the original list
603 // (originally of length 6) since we don't start from event number 0
604 if (!isResetAfterAnalysis) {
605 // Check if we have a list for this choice number
606 // If not we create a new one for it
607 if (!backtrackMap.containsKey(conflictEventNumber)) {
608 backtrackChoiceLists = new LinkedList<>();
609 backtrackMap.put(conflictEventNumber, backtrackChoiceLists);
611 backtrackChoiceLists = backtrackMap.get(conflictEventNumber);
613 int maxListLength = choiceUpperBound + 1;
614 int listLength = maxListLength - conflictEventNumber;
615 Integer[] newChoiceList = new Integer[listLength];
616 // Put the conflicting event numbers first and reverse the order
617 newChoiceList[0] = refChoices[currentChoice];
618 newChoiceList[1] = refChoices[conflictEventNumber];
619 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
620 for (int i = conflictEventNumber + 1, j = 2; j < listLength; i++) {
621 if (refChoices[i] != refChoices[currentChoice]) {
622 newChoiceList[j] = refChoices[i];
626 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
627 // The start index for the recursion is always 1 (from the main branch)
628 } else { // This is a sub-graph
629 // There is a case/bug that after a re-initialization, currCG is not yet initialized
630 if (currCG != null && cgMap.containsKey(currCG)) {
631 int backtrackListIndex = cgMap.get(currCG);
632 backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
633 int listLength = refChoices.length;
634 Integer[] newChoiceList = new Integer[listLength];
635 // Copy everything before the conflict number
636 for (int i = 0; i < conflictEventNumber; i++) {
637 newChoiceList[i] = refChoices[i];
639 // Put the conflicting events
640 newChoiceList[conflictEventNumber] = refChoices[currentChoice];
641 newChoiceList[conflictEventNumber + 1] = refChoices[conflictEventNumber];
643 for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
644 if (refChoices[i] != refChoices[currentChoice]) {
645 newChoiceList[j] = refChoices[i];
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 % refChoices.length) - 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(refChoices[eventNumber])) {
763 ReadWriteSet rwSet = readWriteFieldsMap.get(refChoices[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() || isReachableInVODGraph(refChoices[currentChoice], refChoices[currentChoice-1])) {
775 createBacktrackChoiceList(currentChoice, eventNumber);
776 // Break if a conflict is found!