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 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 DPORStateReducer extends ListenerAdapter {
51 // Information printout fields for verbose mode
52 private boolean verboseMode;
53 private boolean stateReductionMode;
54 private final PrintWriter out;
55 private String detail;
58 private Transition transition;
60 // DPOR-related fields
62 private Integer[] choices;
63 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
64 private int choiceCounter;
65 private int maxEventChoice;
66 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
67 private HashSet<Integer> currVisitedStates; // States being visited in the current execution
68 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
69 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
70 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
71 // Data structure to analyze field Read/Write accesses and conflicts
72 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
73 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
74 private ArrayList<BacktrackPoint> backtrackPointList; // Record backtrack points (CG, state Id, and choice)
75 private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
76 private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
77 private HashMap<Integer,Integer> newStateEventMap; // Record event producing a new state ID
78 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
79 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
81 // Visible operation dependency graph implementation (SPIN paper) related fields
82 private int currChoiceValue;
83 private int prevChoiceValue;
84 private HashMap<Integer, HashSet<Integer>> vodGraphMap; // Visible operation dependency graph (VOD graph)
87 private boolean isBooleanCGFlipped;
88 private boolean isEndOfExecution;
91 private int numOfTransitions;
93 public DPORStateReducer(Config config, JPF jpf) {
94 verboseMode = config.getBoolean("printout_state_transition", false);
95 stateReductionMode = config.getBoolean("activate_state_reduction", true);
97 out = new PrintWriter(System.out, true);
101 isBooleanCGFlipped = false;
102 numOfTransitions = 0;
103 restorableStateMap = new HashMap<>();
104 initializeStatesVariables();
108 public void stateRestored(Search search) {
110 id = search.getStateId();
111 depth = search.getDepth();
112 transition = search.getTransition();
114 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
115 " and depth: " + depth + "\n");
120 public void searchStarted(Search search) {
122 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
127 public void stateAdvanced(Search search) {
129 id = search.getStateId();
130 depth = search.getDepth();
131 transition = search.getTransition();
132 if (search.isNewState()) {
138 if (search.isEndState()) {
139 out.println("\n==> DEBUG: This is the last state!\n");
142 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
143 " which is " + detail + " Transition: " + transition + "\n");
145 if (stateReductionMode) {
146 updateStateInfo(search);
151 public void stateBacktracked(Search search) {
153 id = search.getStateId();
154 depth = search.getDepth();
155 transition = search.getTransition();
158 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
159 " and depth: " + depth + "\n");
161 if (stateReductionMode) {
162 updateStateInfo(search);
167 public void searchFinished(Search search) {
169 out.println("\n==> DEBUG: ----------------------------------- search finished");
170 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
171 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
172 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
177 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
178 if (stateReductionMode) {
179 // Initialize with necessary information from the CG
180 if (nextCG instanceof IntChoiceFromSet) {
181 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
182 if (!isEndOfExecution) {
183 // Check if CG has been initialized, otherwise initialize it
184 Integer[] cgChoices = icsCG.getAllChoices();
185 // Record the events (from choices)
186 if (choices == null) {
188 // Make a copy of choices as reference
189 refChoices = copyChoices(choices);
190 // Record the max event choice (the last element of the choice array)
191 maxEventChoice = choices[choices.length - 1];
193 icsCG.setNewValues(choices);
195 // Use a modulo since choiceCounter is going to keep increasing
196 int choiceIndex = choiceCounter % choices.length;
197 icsCG.advance(choices[choiceIndex]);
199 // Set done all CGs while transitioning to a new execution
207 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
209 if (stateReductionMode) {
210 // Check the boolean CG and if it is flipped, we are resetting the analysis
211 if (currentCG instanceof BooleanChoiceGenerator) {
212 if (!isBooleanCGFlipped) {
213 isBooleanCGFlipped = true;
215 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
216 initializeStatesVariables();
219 // Check every choice generated and ensure fair scheduling!
220 if (currentCG instanceof IntChoiceFromSet) {
221 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
222 // If this is a new CG then we need to update data structures
223 resetStatesForNewExecution(icsCG, vm);
224 // If we don't see a fair scheduling of events/choices then we have to enforce it
225 fairSchedulingAndBacktrackPoint(icsCG, vm);
226 // Map state to event
227 mapStateToEvent(icsCG.getNextChoice());
228 // Explore the next backtrack point:
229 // 1) if we have seen this state or this state contains cycles that involve all events, and
230 // 2) after the current CG is advanced at least once
231 if (terminateCurrentExecution() && choiceCounter > 0) {
232 exploreNextBacktrackPoints(vm, icsCG);
236 justVisitedStates.clear();
245 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
246 if (stateReductionMode) {
247 if (!isEndOfExecution) {
248 // Has to be initialized and a integer CG
249 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
250 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
251 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
252 if (currentChoice < 0) { // If choice is -1 then skip
255 currentChoice = checkAndAdjustChoice(currentChoice, vm);
256 // Record accesses from executed instructions
257 if (executedInsn instanceof JVMFieldInstruction) {
258 // Analyze only after being initialized
259 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
260 // We don't care about libraries
261 if (!isFieldExcluded(fieldClass)) {
262 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
264 } else if (executedInsn instanceof INVOKEINTERFACE) {
265 // Handle the read/write accesses that occur through iterators
266 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
268 // Analyze conflicts from next instructions
269 if (nextInsn instanceof JVMFieldInstruction) {
270 // Skip the constructor because it is called once and does not have shared access with other objects
271 if (!nextInsn.getMethodInfo().getName().equals("<init>")) {
272 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
273 if (!isFieldExcluded(fieldClass)) {
274 // Check for conflict (go backward from current choice and get the first conflict)
275 for (int eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
276 // Check for conflicts with Write fields for both Read and Write instructions
277 // Check and record a backtrack set for just once!
278 if (isConflictFound(nextInsn, eventCounter, currentChoice, fieldClass) &&
279 isNewConflict(currentChoice, eventCounter)) {
280 // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
281 if (vm.isNewState() || isReachableInVODGraph(currentChoice, vm)) {
282 createBacktrackingPoint(currentChoice, eventCounter);
299 // This class compactly stores Read and Write field sets
300 // We store the field name and its object ID
301 // Sharing the same field means the same field name and object ID
302 private class ReadWriteSet {
303 private HashMap<String, Integer> readSet;
304 private HashMap<String, Integer> writeSet;
306 public ReadWriteSet() {
307 readSet = new HashMap<>();
308 writeSet = new HashMap<>();
311 public void addReadField(String field, int objectId) {
312 readSet.put(field, objectId);
315 public void addWriteField(String field, int objectId) {
316 writeSet.put(field, objectId);
319 public boolean readFieldExists(String field) {
320 return readSet.containsKey(field);
323 public boolean writeFieldExists(String field) {
324 return writeSet.containsKey(field);
327 public int readFieldObjectId(String field) {
328 return readSet.get(field);
331 public int writeFieldObjectId(String field) {
332 return writeSet.get(field);
336 // This class compactly stores backtrack points: 1) backtrack state ID, and 2) backtracking choices
337 private class BacktrackPoint {
338 private IntChoiceFromSet backtrackCG; // CG at this backtrack point
339 private int stateId; // State at this backtrack point
340 private int choice; // Choice chosen at this backtrack point
342 public BacktrackPoint(IntChoiceFromSet cg, int stId, int cho) {
348 public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
350 public int getStateId() {
354 public int getChoice() {
360 private final static String DO_CALL_METHOD = "doCall";
361 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
362 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
363 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
364 // Groovy library created fields
365 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
367 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
368 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
369 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
370 // Java and Groovy libraries
371 { "java", "org", "sun", "com", "gov", "groovy"};
372 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
373 private final static String GET_PROPERTY_METHOD =
374 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
375 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
376 private final static String JAVA_INTEGER = "int";
377 private final static String JAVA_STRING_LIB = "java.lang.String";
380 private void fairSchedulingAndBacktrackPoint(IntChoiceFromSet icsCG, VM vm) {
381 // Check the next choice and if the value is not the same as the expected then force the expected value
382 int choiceIndex = choiceCounter % refChoices.length;
383 int nextChoice = icsCG.getNextChoice();
384 if (refChoices[choiceIndex] != nextChoice) {
385 int expectedChoice = refChoices[choiceIndex];
386 int currCGIndex = icsCG.getNextChoiceIndex();
387 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
388 icsCG.setChoice(currCGIndex, expectedChoice);
391 // Update current choice
392 currChoiceValue = refChoices[choiceIndex];
393 // Record state ID and choice/event as backtrack point
394 int stateId = vm.getStateId();
395 backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex]));
396 // Store restorable state object for this state (always store the latest)
397 RestorableVMState restorableState = vm.getRestorableState();
398 restorableStateMap.put(stateId, restorableState);
401 private Integer[] copyChoices(Integer[] choicesToCopy) {
403 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
404 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
405 return copyOfChoices;
408 // --- Functions related to cycle detection
410 // Detect cycles in the current execution/trace
411 // We terminate the execution iff:
412 // (1) the state has been visited in the current execution
413 // (2) the state has one or more cycles that involve all the events
414 // With simple approach we only need to check for a re-visited state.
415 // Basically, we have to check that we have executed all events between two occurrences of such state.
416 private boolean containsCyclesWithAllEvents(int stId) {
418 // False if the state ID hasn't been recorded
419 if (!stateToEventMap.containsKey(stId)) {
422 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
423 // Check if this set contains all the event choices
424 // If not then this is not the terminating condition
425 for(int i=0; i<=maxEventChoice; i++) {
426 if (!visitedEvents.contains(i)) {
433 private void initializeStatesVariables() {
440 currVisitedStates = new HashSet<>();
441 justVisitedStates = new HashSet<>();
442 prevVisitedStates = new HashSet<>();
443 stateToEventMap = new HashMap<>();
445 backtrackMap = new HashMap<>();
446 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
447 backtrackPointList = new ArrayList<>();
448 conflictPairMap = new HashMap<>();
449 doneBacktrackSet = new HashSet<>();
450 newStateEventMap = new HashMap<>();
451 readWriteFieldsMap = new HashMap<>();
454 prevChoiceValue = -1;
455 vodGraphMap = new HashMap<>();
457 isEndOfExecution = false;
460 private void mapStateToEvent(int nextChoiceValue) {
461 // Update all states with this event/choice
462 // This means that all past states now see this transition
463 Set<Integer> stateSet = stateToEventMap.keySet();
464 for(Integer stateId : stateSet) {
465 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
466 eventSet.add(nextChoiceValue);
470 private boolean terminateCurrentExecution() {
471 // We need to check all the states that have just been visited
472 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
473 for(Integer stateId : justVisitedStates) {
474 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
481 private void updateStateInfo(Search search) {
482 // Update the state variables
483 // Line 19 in the paper page 11 (see the heading note above)
484 int stateId = search.getStateId();
485 currVisitedStates.add(stateId);
486 // Insert state ID into the map if it is new
487 if (!stateToEventMap.containsKey(stateId)) {
488 HashSet<Integer> eventSet = new HashSet<>();
489 stateToEventMap.put(stateId, eventSet);
491 justVisitedStates.add(stateId);
492 // Update the VOD graph when there is a new state
493 updateVODGraph(search.getVM());
496 // --- Functions related to Read/Write access analysis on shared fields
498 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList) {
499 // Insert backtrack point to the right state ID
500 LinkedList<Integer[]> backtrackList;
501 if (backtrackMap.containsKey(stateId)) {
502 backtrackList = backtrackMap.get(stateId);
504 backtrackList = new LinkedList<>();
505 backtrackMap.put(stateId, backtrackList);
507 backtrackList.addFirst(newChoiceList);
508 // Add to priority queue
509 if (!backtrackStateQ.contains(stateId)) {
510 backtrackStateQ.add(stateId);
514 // Analyze Read/Write accesses that are directly invoked on fields
515 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
516 // Do the analysis to get Read and Write accesses to fields
517 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
518 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
519 // Record the field in the map
520 if (executedInsn instanceof WriteInstruction) {
521 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
522 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
523 if (fieldClass.startsWith(str)) {
527 rwSet.addWriteField(fieldClass, objectId);
528 } else if (executedInsn instanceof ReadInstruction) {
529 rwSet.addReadField(fieldClass, objectId);
533 // Analyze Read accesses that are indirect (performed through iterators)
534 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
535 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
537 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
538 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
539 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
540 // Extract info from the stack frame
541 StackFrame frame = ti.getTopFrame();
542 int[] frameSlots = frame.getSlots();
543 // Get the Groovy callsite library at index 0
544 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
545 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
548 // Get the iterated object whose property is accessed
549 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
550 if (eiAccessObj == null) {
553 // We exclude library classes (they start with java, org, etc.) and some more
554 String objClassName = eiAccessObj.getClassInfo().getName();
555 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
556 excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName)) {
559 // Extract fields from this object and put them into the read write
560 int numOfFields = eiAccessObj.getNumberOfFields();
561 for(int i=0; i<numOfFields; i++) {
562 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
563 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
564 String fieldClass = fieldInfo.getFullName();
565 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
566 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
567 // Record the field in the map
568 rwSet.addReadField(fieldClass, objectId);
574 private int checkAndAdjustChoice(int currentChoice, VM vm) {
575 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
576 // for certain method calls in the infrastructure, e.g., eventSince()
577 int currChoiceInd = currentChoice % refChoices.length;
578 int currChoiceFromCG = currChoiceInd;
579 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
580 // This is the main event CG
581 if (currentCG instanceof IntIntervalGenerator) {
582 // This is the interval CG used in device handlers
583 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
584 int actualEvtNum = ((IntChoiceFromSet) parentCG).getNextChoice();
585 // Find the index of the event/choice in refChoices
586 for (int i = 0; i<refChoices.length; i++) {
587 if (actualEvtNum == refChoices[i]) {
588 currChoiceFromCG = i;
593 if (currChoiceInd != currChoiceFromCG) {
594 currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
596 return currentChoice;
599 private void createBacktrackingPoint(int currentChoice, int confEvtNum) {
601 // Create a new list of choices for backtrack based on the current choice and conflicting event number
602 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
603 // for the original set {0, 1, 2, 3}
604 Integer[] newChoiceList = new Integer[refChoices.length];
605 // Put the conflicting event numbers first and reverse the order
606 int actualCurrCho = currentChoice % refChoices.length;
607 // We use the actual choices here in case they have been modified/adjusted by the fair scheduling method
608 newChoiceList[0] = choices[actualCurrCho];
609 newChoiceList[1] = backtrackPointList.get(confEvtNum).getChoice();
610 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
611 for (int i = 0, j = 2; i < refChoices.length; i++) {
612 if (refChoices[i] != newChoiceList[0] && refChoices[i] != newChoiceList[1]) {
613 newChoiceList[j] = refChoices[i];
617 // Get the backtrack CG for this backtrack point
618 int stateId = backtrackPointList.get(confEvtNum).getStateId();
619 // Check if this trace has been done starting from this state
620 if (isTraceAlreadyConstructed(newChoiceList, stateId)) {
623 addNewBacktrackPoint(stateId, newChoiceList);
626 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
627 for (String excludedField : excludedStrings) {
628 if (className.contains(excludedField)) {
635 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
636 for (String excludedField : excludedStrings) {
637 if (className.endsWith(excludedField)) {
644 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
645 for (String excludedField : excludedStrings) {
646 if (className.startsWith(excludedField)) {
653 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
655 // Check if we are reaching the end of our execution: no more backtracking points to explore
656 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
657 if (!backtrackStateQ.isEmpty()) {
658 // Set done all the other backtrack points
659 for (BacktrackPoint backtrackPoint : backtrackPointList) {
660 backtrackPoint.getBacktrackCG().setDone();
662 // Reset the next backtrack point with the latest state
663 int hiStateId = backtrackStateQ.peek();
664 // Restore the state first if necessary
665 if (vm.getStateId() != hiStateId) {
666 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
667 vm.restoreState(restorableState);
669 // Set the backtrack CG
670 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
671 setBacktrackCG(hiStateId, backtrackCG);
673 // Set done this last CG (we save a few rounds)
676 // Save all the visited states when starting a new execution of trace
677 prevVisitedStates.addAll(currVisitedStates);
678 currVisitedStates.clear();
679 // This marks a transitional period to the new CG
680 isEndOfExecution = true;
683 private ReadWriteSet getReadWriteSet(int currentChoice) {
684 // Do the analysis to get Read and Write accesses to fields
686 // We already have an entry
687 if (readWriteFieldsMap.containsKey(currentChoice)) {
688 rwSet = readWriteFieldsMap.get(currentChoice);
689 } else { // We need to create a new entry
690 rwSet = new ReadWriteSet();
691 readWriteFieldsMap.put(currentChoice, rwSet);
696 private boolean isConflictFound(Instruction nextInsn, int eventCounter, int currentChoice, String fieldClass) {
698 int actualCurrCho = currentChoice % refChoices.length;
699 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
700 if (!readWriteFieldsMap.containsKey(eventCounter) ||
701 choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
704 ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
705 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
706 // Check for conflicts with Write fields for both Read and Write instructions
707 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
708 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
709 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
710 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
716 private boolean isFieldExcluded(String field) {
717 // Check against "starts-with", "ends-with", and "contains" list
718 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
719 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
720 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
727 private boolean isNewConflict(int currentEvent, int eventNumber) {
728 HashSet<Integer> conflictSet;
729 if (!conflictPairMap.containsKey(currentEvent)) {
730 conflictSet = new HashSet<>();
731 conflictPairMap.put(currentEvent, conflictSet);
733 conflictSet = conflictPairMap.get(currentEvent);
735 // If this conflict has been recorded before, we return false because
736 // we don't want to save this backtrack point twice
737 if (conflictSet.contains(eventNumber)) {
740 // If it hasn't been recorded, then do otherwise
741 conflictSet.add(eventNumber);
745 private boolean isTraceAlreadyConstructed(Integer[] choiceList, int stateId) {
746 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
747 // TODO: THIS IS AN OPTIMIZATION!
748 // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
749 // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
750 // The second time this event 1 is explored, it will generate the same state as the first one
751 StringBuilder sb = new StringBuilder();
754 sb.append(choiceList[0]);
755 // Check if the trace has been constructed as a backtrack point for this state
756 if (doneBacktrackSet.contains(sb.toString())) {
759 doneBacktrackSet.add(sb.toString());
763 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
764 if (choices == null || choices != icsCG.getAllChoices()) {
765 // Reset state variables
767 choices = icsCG.getAllChoices();
768 refChoices = copyChoices(choices);
769 // Clearing data structures
770 conflictPairMap.clear();
771 readWriteFieldsMap.clear();
772 stateToEventMap.clear();
773 isEndOfExecution = false;
774 backtrackPointList.clear();
778 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
779 // Set a backtrack CG based on a state ID
780 LinkedList<Integer[]> backtrackChoices = backtrackMap.get(stateId);
781 backtrackCG.setNewValues(backtrackChoices.removeLast()); // Get the last from the queue
782 backtrackCG.setStateId(stateId);
784 // Remove from the queue if we don't have more backtrack points for that state
785 if (backtrackChoices.isEmpty()) {
786 backtrackMap.remove(stateId);
787 backtrackStateQ.remove(stateId);
791 // --- Functions related to the visible operation dependency graph implementation discussed in the SPIN paper
793 // This method checks whether a choice/event (transition) is reachable from the choice/event that produces
794 // the state right before this state in the VOD graph
795 // We use a BFS algorithm for this purpose
796 private boolean isReachableInVODGraph(int currentChoice, VM vm) {
798 int choiceIndex = currentChoice % refChoices.length;
799 int currEvent = refChoices[choiceIndex];
801 int stateId = vm.getStateId(); // A state that has been seen
802 int prevEvent = newStateEventMap.get(stateId);
803 // Only start traversing the graph if prevEvent has an outgoing edge
804 if (vodGraphMap.containsKey(prevEvent)) {
805 // Record visited choices as we search in the graph
806 HashSet<Integer> visitedChoice = new HashSet<>();
807 visitedChoice.add(prevEvent);
808 // Get the first nodes to visit (the neighbors of prevEvent)
809 LinkedList<Integer> nodesToVisit = new LinkedList<>();
810 nodesToVisit.addAll(vodGraphMap.get(prevEvent));
811 // Traverse the graph using BFS
812 while (!nodesToVisit.isEmpty()) {
813 int choice = nodesToVisit.removeFirst();
814 if (choice == currEvent) {
817 if (visitedChoice.contains(choice)) { // If there is a loop then just continue the exploration
820 // Continue searching
821 visitedChoice.add(choice);
822 HashSet<Integer> choiceNextNodes = vodGraphMap.get(choice);
823 if (choiceNextNodes != null) {
824 // Add only if there is a mapping for next nodes
825 for (Integer nextNode : choiceNextNodes) {
827 if (nextNode == choice) {
830 nodesToVisit.addLast(nextNode);
838 private void updateVODGraph(VM vm) {
839 // Do this only if it is a new state
840 if (vm.isNewState()) {
841 // Update the graph when we have the current choice value
842 HashSet<Integer> choiceSet;
843 if (vodGraphMap.containsKey(prevChoiceValue)) {
844 // If the key already exists, just retrieve it
845 choiceSet = vodGraphMap.get(prevChoiceValue);
847 // Create a new entry
848 choiceSet = new HashSet<>();
849 vodGraphMap.put(prevChoiceValue, choiceSet);
851 choiceSet.add(currChoiceValue);
852 prevChoiceValue = currChoiceValue;
853 // Map this state ID to the event (transition) that produces it
854 newStateEventMap.put(vm.getStateId(), currChoiceValue);