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;
29 import gov.nasa.jpf.vm.choice.IntIntervalGenerator;
31 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 have a graph G
43 * (i.e., visible operation dependency graph).
44 * This DPOR implementation actually fixes the algorithm in the SPIN paper that does not
45 * consider cases where a state could be matched early. In this new algorithm/implementation,
46 * each run is terminated iff:
47 * - we find a state that matches a state in a previous run, or
48 * - we have a matched state in the current run that consists of cycles that contain all choices/events.
50 public class DPORStateReducer extends ListenerAdapter {
52 // Information printout fields for verbose mode
53 private boolean verboseMode;
54 private boolean stateReductionMode;
55 private final PrintWriter out;
56 private String detail;
59 private Transition transition;
61 // DPOR-related fields
63 private Integer[] choices;
64 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
65 private int choiceCounter;
66 private int maxEventChoice;
67 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
68 private HashSet<Integer> currVisitedStates; // States being visited in the current execution
69 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
70 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
71 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
72 // Data structure to analyze field Read/Write accesses and conflicts
73 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
74 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
75 private ArrayList<BacktrackPoint> backtrackPointList; // Record backtrack points (CG, state Id, and choice)
76 private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
77 private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
78 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
79 private HashMap<Integer, RestorableState> restorableStateMap; // Maps state IDs to the restorable state object
82 private boolean isBooleanCGFlipped;
83 private boolean isEndOfExecution;
86 private int numOfConflicts;
87 private int numOfTransitions;
89 public DPORStateReducer(Config config, JPF jpf) {
90 verboseMode = config.getBoolean("printout_state_transition", false);
91 stateReductionMode = config.getBoolean("activate_state_reduction", true);
93 out = new PrintWriter(System.out, true);
97 isBooleanCGFlipped = false;
100 restorableStateMap = new HashMap<>();
101 initializeStatesVariables();
105 public void stateRestored(Search search) {
107 id = search.getStateId();
108 depth = search.getDepth();
109 transition = search.getTransition();
111 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
112 " and depth: " + depth + "\n");
117 public void searchStarted(Search search) {
119 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
124 public void stateAdvanced(Search search) {
126 id = search.getStateId();
127 depth = search.getDepth();
128 transition = search.getTransition();
129 if (search.isNewState()) {
135 if (search.isEndState()) {
136 out.println("\n==> DEBUG: This is the last state!\n");
139 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
140 " which is " + detail + " Transition: " + transition + "\n");
142 if (stateReductionMode) {
143 updateStateInfo(search);
148 public void stateBacktracked(Search search) {
150 id = search.getStateId();
151 depth = search.getDepth();
152 transition = search.getTransition();
155 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
156 " and depth: " + depth + "\n");
158 if (stateReductionMode) {
159 updateStateInfo(search);
164 public void searchFinished(Search search) {
165 if (stateReductionMode) {
166 // Number of conflicts = first trace + subsequent backtrack points
167 numOfConflicts += 1 + doneBacktrackSet.size();
170 out.println("\n==> DEBUG: ----------------------------------- search finished");
171 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
172 out.println("\n==> DEBUG: Number of conflicts : " + numOfConflicts);
173 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
174 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
179 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
180 if (stateReductionMode) {
181 // Initialize with necessary information from the CG
182 if (nextCG instanceof IntChoiceFromSet) {
183 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
184 if (!isEndOfExecution) {
185 // Check if CG has been initialized, otherwise initialize it
186 Integer[] cgChoices = icsCG.getAllChoices();
187 // Record the events (from choices)
188 if (choices == null) {
190 // Make a copy of choices as reference
191 refChoices = copyChoices(choices);
192 // Record the max event choice (the last element of the choice array)
193 maxEventChoice = choices[choices.length - 1];
195 icsCG.setNewValues(choices);
197 // Use a modulo since choiceCounter is going to keep increasing
198 int choiceIndex = choiceCounter % choices.length;
199 icsCG.advance(choices[choiceIndex]);
201 // Set done all CGs while transitioning to a new execution
209 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
211 if (stateReductionMode) {
212 // Check the boolean CG and if it is flipped, we are resetting the analysis
213 if (currentCG instanceof BooleanChoiceGenerator) {
214 if (!isBooleanCGFlipped) {
215 isBooleanCGFlipped = true;
217 // Number of conflicts = first trace + subsequent backtrack points
218 numOfConflicts = 1 + doneBacktrackSet.size();
219 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
220 initializeStatesVariables();
223 // Check every choice generated and ensure fair scheduling!
224 if (currentCG instanceof IntChoiceFromSet) {
225 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
226 // If this is a new CG then we need to update data structures
227 resetStatesForNewExecution(icsCG, vm);
228 // If we don't see a fair scheduling of events/choices then we have to enforce it
229 fairSchedulingAndBacktrackPoint(icsCG, vm);
230 // Map state to event
231 mapStateToEvent(icsCG.getNextChoice());
232 // Explore the next backtrack point:
233 // 1) if we have seen this state or this state contains cycles that involve all events, and
234 // 2) after the current CG is advanced at least once
235 if (terminateCurrentExecution() && choiceCounter > 0) {
236 exploreNextBacktrackPoints(vm, icsCG);
240 justVisitedStates.clear();
249 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
250 if (stateReductionMode) {
251 if (!isEndOfExecution) {
252 // Has to be initialized and a integer CG
253 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
254 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
255 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
256 if (currentChoice < 0) { // If choice is -1 then skip
259 currentChoice = checkAndAdjustChoice(currentChoice, vm);
260 // Record accesses from executed instructions
261 if (executedInsn instanceof JVMFieldInstruction) {
262 // Analyze only after being initialized
263 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
264 // We don't care about libraries
265 if (!isFieldExcluded(fieldClass)) {
266 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
268 } else if (executedInsn instanceof INVOKEINTERFACE) {
269 // Handle the read/write accesses that occur through iterators
270 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
272 // Analyze conflicts from next instructions
273 if (nextInsn instanceof JVMFieldInstruction) {
274 // Skip the constructor because it is called once and does not have shared access with other objects
275 if (!nextInsn.getMethodInfo().getName().equals("<init>")) {
276 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
277 if (!isFieldExcluded(fieldClass)) {
278 // Check for conflict (go backward from current choice and get the first conflict)
279 for (int eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
280 // Check for conflicts with Write fields for both Read and Write instructions
281 // Check and record a backtrack set for just once!
282 if (isConflictFound(nextInsn, eventCounter, currentChoice, fieldClass) &&
283 isNewConflict(currentChoice, eventCounter)) {
284 createBacktrackingPoint(currentChoice, eventCounter);
300 // This class compactly stores Read and Write field sets
301 // We store the field name and its object ID
302 // Sharing the same field means the same field name and object ID
303 private class ReadWriteSet {
304 private HashMap<String, Integer> readSet;
305 private HashMap<String, Integer> writeSet;
307 public ReadWriteSet() {
308 readSet = new HashMap<>();
309 writeSet = new HashMap<>();
312 public void addReadField(String field, int objectId) {
313 readSet.put(field, objectId);
316 public void addWriteField(String field, int objectId) {
317 writeSet.put(field, objectId);
320 public Set<String> getReadSet() {
321 return readSet.keySet();
324 public Set<String> getWriteSet() {
325 return writeSet.keySet();
328 public boolean readFieldExists(String field) {
329 return readSet.containsKey(field);
332 public boolean writeFieldExists(String field) {
333 return writeSet.containsKey(field);
336 public int readFieldObjectId(String field) {
337 return readSet.get(field);
340 public int writeFieldObjectId(String field) {
341 return writeSet.get(field);
345 // This class compactly stores backtrack points: 1) backtrack state ID, and 2) backtracking choices
346 private class BacktrackPoint {
347 private IntChoiceFromSet backtrackCG; // CG at this backtrack point
348 private int stateId; // State at this backtrack point
349 private int choice; // Choice chosen at this backtrack point
351 public BacktrackPoint(IntChoiceFromSet cg, int stId, int cho) {
357 public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
359 public int getStateId() {
363 public int getChoice() {
368 // This class compactly stores: 1) restorable VM state, and 2) global choice counter
369 private class RestorableState {
370 private RestorableVMState restorableState;
371 private int choiceCounter;
373 public RestorableState (RestorableVMState restState, int choCtr) {
374 restorableState = restState;
375 choiceCounter = choCtr;
378 public RestorableVMState getRestorableState() {
379 return restorableState;
382 public int getChoiceCounter() {
383 return choiceCounter;
388 private final static String DO_CALL_METHOD = "doCall";
389 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
390 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
391 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
392 // Groovy library created fields
393 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
395 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
396 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
397 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
398 // Java and Groovy libraries
399 { "java", "org", "sun", "com", "gov", "groovy"};
400 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
401 private final static String GET_PROPERTY_METHOD =
402 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
403 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
404 private final static String JAVA_INTEGER = "int";
405 private final static String JAVA_STRING_LIB = "java.lang.String";
408 private void fairSchedulingAndBacktrackPoint(IntChoiceFromSet icsCG, VM vm) {
409 // Check the next choice and if the value is not the same as the expected then force the expected value
410 int choiceIndex = choiceCounter % refChoices.length;
411 int nextChoice = icsCG.getNextChoice();
412 if (refChoices[choiceIndex] != nextChoice) {
413 int expectedChoice = refChoices[choiceIndex];
414 int currCGIndex = icsCG.getNextChoiceIndex();
415 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
416 icsCG.setChoice(currCGIndex, expectedChoice);
419 // Record state ID and choice/event as backtrack point
420 int stateId = vm.getStateId();
421 backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex]));
422 // Store restorable state object for this state (always store the latest)
423 RestorableVMState restorableState = vm.getRestorableState();
424 restorableStateMap.put(stateId, new RestorableState(restorableState, choiceCounter));
427 private Integer[] copyChoices(Integer[] choicesToCopy) {
429 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
430 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
431 return copyOfChoices;
434 // --- Functions related to cycle detection
436 // Detect cycles in the current execution/trace
437 // We terminate the execution iff:
438 // (1) the state has been visited in the current execution
439 // (2) the state has one or more cycles that involve all the events
440 // With simple approach we only need to check for a re-visited state.
441 // Basically, we have to check that we have executed all events between two occurrences of such state.
442 private boolean containsCyclesWithAllEvents(int stId) {
444 // False if the state ID hasn't been recorded
445 if (!stateToEventMap.containsKey(stId)) {
448 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
449 // Check if this set contains all the event choices
450 // If not then this is not the terminating condition
451 for(int i=0; i<=maxEventChoice; i++) {
452 if (!visitedEvents.contains(i)) {
459 private void initializeStatesVariables() {
466 currVisitedStates = new HashSet<>();
467 justVisitedStates = new HashSet<>();
468 prevVisitedStates = new HashSet<>();
469 stateToEventMap = new HashMap<>();
471 backtrackMap = new HashMap<>();
472 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
473 backtrackPointList = new ArrayList<>();
474 conflictPairMap = new HashMap<>();
475 doneBacktrackSet = new HashSet<>();
476 readWriteFieldsMap = new HashMap<>();
478 isEndOfExecution = false;
481 private void mapStateToEvent(int nextChoiceValue) {
482 // Update all states with this event/choice
483 // This means that all past states now see this transition
484 Set<Integer> stateSet = stateToEventMap.keySet();
485 for(Integer stateId : stateSet) {
486 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
487 eventSet.add(nextChoiceValue);
491 private boolean terminateCurrentExecution() {
492 // We need to check all the states that have just been visited
493 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
494 for(Integer stateId : justVisitedStates) {
495 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
502 private void updateStateInfo(Search search) {
503 // Update the state variables
504 // Line 19 in the paper page 11 (see the heading note above)
505 int stateId = search.getStateId();
506 currVisitedStates.add(stateId);
507 // Insert state ID into the map if it is new
508 if (!stateToEventMap.containsKey(stateId)) {
509 HashSet<Integer> eventSet = new HashSet<>();
510 stateToEventMap.put(stateId, eventSet);
512 justVisitedStates.add(stateId);
513 analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
516 // --- Functions related to Read/Write access analysis on shared fields
518 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList) {
519 // Insert backtrack point to the right state ID
520 LinkedList<Integer[]> backtrackList;
521 if (backtrackMap.containsKey(stateId)) {
522 backtrackList = backtrackMap.get(stateId);
524 backtrackList = new LinkedList<>();
525 backtrackMap.put(stateId, backtrackList);
527 backtrackList.addFirst(newChoiceList);
528 // Add to priority queue
529 if (!backtrackStateQ.contains(stateId)) {
530 backtrackStateQ.add(stateId);
534 // Analyze Read/Write accesses that are directly invoked on fields
535 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
536 // Do the analysis to get Read and Write accesses to fields
537 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
538 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
539 // Record the field in the map
540 if (executedInsn instanceof WriteInstruction) {
541 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
542 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
543 if (fieldClass.startsWith(str)) {
547 rwSet.addWriteField(fieldClass, objectId);
548 } else if (executedInsn instanceof ReadInstruction) {
549 rwSet.addReadField(fieldClass, objectId);
553 // Analyze Read accesses that are indirect (performed through iterators)
554 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
555 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
557 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
558 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
559 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
560 // Extract info from the stack frame
561 StackFrame frame = ti.getTopFrame();
562 int[] frameSlots = frame.getSlots();
563 // Get the Groovy callsite library at index 0
564 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
565 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
568 // Get the iterated object whose property is accessed
569 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
570 if (eiAccessObj == null) {
573 // We exclude library classes (they start with java, org, etc.) and some more
574 String objClassName = eiAccessObj.getClassInfo().getName();
575 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
576 excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName)) {
579 // Extract fields from this object and put them into the read write
580 int numOfFields = eiAccessObj.getNumberOfFields();
581 for(int i=0; i<numOfFields; i++) {
582 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
583 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
584 String fieldClass = fieldInfo.getFullName();
585 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
586 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
587 // Record the field in the map
588 rwSet.addReadField(fieldClass, objectId);
594 private int checkAndAdjustChoice(int currentChoice, VM vm) {
595 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
596 // for certain method calls in the infrastructure, e.g., eventSince()
597 int currChoiceInd = currentChoice % refChoices.length;
598 int currChoiceFromCG = currChoiceInd;
599 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
600 // This is the main event CG
601 if (currentCG instanceof IntIntervalGenerator) {
602 // This is the interval CG used in device handlers
603 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
604 int actualEvtNum = ((IntChoiceFromSet) parentCG).getNextChoice();
605 // Find the index of the event/choice in refChoices
606 for (int i = 0; i<refChoices.length; i++) {
607 if (actualEvtNum == refChoices[i]) {
608 currChoiceFromCG = i;
613 if (currChoiceInd != currChoiceFromCG) {
614 currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
616 return currentChoice;
619 private void createBacktrackingPoint(int currentChoice, int confEvtNum) {
621 // Create a new list of choices for backtrack based on the current choice and conflicting event number
622 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
623 // for the original set {0, 1, 2, 3}
624 Integer[] newChoiceList = new Integer[refChoices.length];
625 // Put the conflicting event numbers first and reverse the order
626 int actualCurrCho = currentChoice % refChoices.length;
627 // We use the actual choices here in case they have been modified/adjusted by the fair scheduling method
628 newChoiceList[0] = choices[actualCurrCho];
629 newChoiceList[1] = backtrackPointList.get(confEvtNum).getChoice();
630 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
631 for (int i = 0, j = 2; i < refChoices.length; i++) {
632 if (refChoices[i] != newChoiceList[0] && refChoices[i] != newChoiceList[1]) {
633 newChoiceList[j] = refChoices[i];
637 // Get the backtrack CG for this backtrack point
638 int stateId = backtrackPointList.get(confEvtNum).getStateId();
639 // Check if this trace has been done starting from this state
640 if (isTraceAlreadyConstructed(newChoiceList, stateId)) {
643 addNewBacktrackPoint(stateId, newChoiceList);
646 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
647 for (String excludedField : excludedStrings) {
648 if (className.contains(excludedField)) {
655 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
656 for (String excludedField : excludedStrings) {
657 if (className.endsWith(excludedField)) {
664 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
665 for (String excludedField : excludedStrings) {
666 if (className.startsWith(excludedField)) {
673 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
675 // Check if we are reaching the end of our execution: no more backtracking points to explore
676 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
677 if (!backtrackStateQ.isEmpty()) {
678 // Set done all the other backtrack points
679 for (BacktrackPoint backtrackPoint : backtrackPointList) {
680 backtrackPoint.getBacktrackCG().setDone();
682 // Reset the next backtrack point with the latest state
683 int hiStateId = backtrackStateQ.peek();
684 // Restore the state first if necessary
685 if (vm.getStateId() != hiStateId) {
686 RestorableVMState restorableState = restorableStateMap.get(hiStateId).getRestorableState();
687 vm.restoreState(restorableState);
689 // Set the backtrack CG
690 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
691 setBacktrackCG(hiStateId, backtrackCG);
693 // Set done this last CG (we save a few rounds)
696 // Save all the visited states when starting a new execution of trace
697 prevVisitedStates.addAll(currVisitedStates);
698 currVisitedStates.clear();
699 // This marks a transitional period to the new CG
700 isEndOfExecution = true;
703 private ReadWriteSet getReadWriteSet(int currentChoice) {
704 // Do the analysis to get Read and Write accesses to fields
706 // We already have an entry
707 if (readWriteFieldsMap.containsKey(currentChoice)) {
708 rwSet = readWriteFieldsMap.get(currentChoice);
709 } else { // We need to create a new entry
710 rwSet = new ReadWriteSet();
711 readWriteFieldsMap.put(currentChoice, rwSet);
716 private boolean isConflictFound(int eventCounter, int currentChoice) {
718 int actualCurrCho = currentChoice % refChoices.length;
719 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
720 if (!readWriteFieldsMap.containsKey(eventCounter) ||
721 choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
725 ReadWriteSet currRWSet = readWriteFieldsMap.get(currentChoice);
726 // R/W set of choice/event that may have a potential conflict
727 ReadWriteSet evtRWSet = readWriteFieldsMap.get(eventCounter);
728 // Check for conflicts with Read and Write fields for Write instructions
729 Set<String> currWriteSet = currRWSet.getWriteSet();
730 for(String writeField : currWriteSet) {
731 int currObjId = currRWSet.writeFieldObjectId(writeField);
732 if ((evtRWSet.readFieldExists(writeField) && evtRWSet.readFieldObjectId(writeField) == currObjId) ||
733 (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId)) {
737 // Check for conflicts with Write fields for Read instructions
738 Set<String> currReadSet = currRWSet.getReadSet();
739 for(String readField : currReadSet) {
740 int currObjId = currRWSet.readFieldObjectId(readField);
741 if (evtRWSet.writeFieldExists(readField) && evtRWSet.writeFieldObjectId(readField) == currObjId) {
745 // Return false if no conflict is found
749 private boolean isConflictFound(Instruction nextInsn, int eventCounter, int currentChoice, String fieldClass) {
751 int actualCurrCho = currentChoice % refChoices.length;
752 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
753 if (!readWriteFieldsMap.containsKey(eventCounter) ||
754 choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
757 ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
758 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
759 // Check for conflicts with Write fields for both Read and Write instructions
760 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
761 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
762 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
763 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
769 private boolean isFieldExcluded(String field) {
770 // Check against "starts-with", "ends-with", and "contains" list
771 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
772 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
773 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
780 private boolean isNewConflict(int currentEvent, int eventNumber) {
781 HashSet<Integer> conflictSet;
782 if (!conflictPairMap.containsKey(currentEvent)) {
783 conflictSet = new HashSet<>();
784 conflictPairMap.put(currentEvent, conflictSet);
786 conflictSet = conflictPairMap.get(currentEvent);
788 // If this conflict has been recorded before, we return false because
789 // we don't want to save this backtrack point twice
790 if (conflictSet.contains(eventNumber)) {
793 // If it hasn't been recorded, then do otherwise
794 conflictSet.add(eventNumber);
798 private boolean isTraceAlreadyConstructed(Integer[] choiceList, int stateId) {
799 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
800 // TODO: THIS IS AN OPTIMIZATION!
801 // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
802 // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
803 // The second time this event 1 is explored, it will generate the same state as the first one
804 StringBuilder sb = new StringBuilder();
807 sb.append(choiceList[0]);
808 // Check if the trace has been constructed as a backtrack point for this state
809 if (doneBacktrackSet.contains(sb.toString())) {
812 doneBacktrackSet.add(sb.toString());
816 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
817 if (choices == null || choices != icsCG.getAllChoices()) {
818 // Reset state variables
820 choices = icsCG.getAllChoices();
821 refChoices = copyChoices(choices);
822 // Clearing data structures
823 conflictPairMap.clear();
824 readWriteFieldsMap.clear();
825 stateToEventMap.clear();
826 isEndOfExecution = false;
827 backtrackPointList.clear();
831 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
832 // Set a backtrack CG based on a state ID
833 LinkedList<Integer[]> backtrackChoices = backtrackMap.get(stateId);
834 backtrackCG.setNewValues(backtrackChoices.removeLast()); // Get the last from the queue
835 backtrackCG.setStateId(stateId);
837 // Remove from the queue if we don't have more backtrack points for that state
838 if (backtrackChoices.isEmpty()) {
839 backtrackMap.remove(stateId);
840 backtrackStateQ.remove(stateId);
844 // --- Functions related to the reachability analysis when there is a state match
846 // We use backtrackPointsList to analyze the reachable states/events when there is a state match:
847 // 1) Whenever there is state match, there is a cycle of events
848 // 2) We need to analyze and find conflicts for the reachable choices/events in the cycle
849 // 3) Then we create a new backtrack point for every new conflict
850 private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
851 // Perform this analysis only when there is a state match
852 if (!vm.isNewState()) {
853 if (restorableStateMap.containsKey(stateId)) {
854 // Find the choice/event that marks the start of this cycle: first choice we explore for conflicts
855 int conflictChoice = restorableStateMap.get(stateId).getChoiceCounter();
856 int currentChoice = choiceCounter - 1;
857 // Find conflicts between choices/events in this cycle (we scan forward in the cycle, not backward)
858 while (conflictChoice < currentChoice) {
859 for (int eventCounter = conflictChoice + 1; eventCounter <= currentChoice; eventCounter++) {
860 if (isConflictFound(eventCounter, conflictChoice) && isNewConflict(conflictChoice, eventCounter)) {
861 createBacktrackingPoint(conflictChoice, eventCounter);