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.FileWriter;
32 import java.io.PrintWriter;
34 import java.util.logging.Logger;
35 import java.io.IOException;
37 // TODO: Fix for Groovy's model-checking
38 // TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
40 * Simple tool to log state changes.
42 * This DPOR implementation is augmented by the algorithm presented in this SPIN paper:
43 * http://spinroot.com/spin/symposia/ws08/spin2008_submission_33.pdf
45 * The algorithm is presented on page 11 of the paper. Basically, we have a graph G
46 * (i.e., visible operation dependency graph).
47 * This DPOR implementation actually fixes the algorithm in the SPIN paper that does not
48 * consider cases where a state could be matched early. In this new algorithm/implementation,
49 * each run is terminated iff:
50 * - we find a state that matches a state in a previous run, or
51 * - we have a matched state in the current run that consists of cycles that contain all choices/events.
53 public class DPORStateReducer extends ListenerAdapter {
55 // Information printout fields for verbose mode
56 private boolean verboseMode;
57 private boolean stateReductionMode;
58 private final PrintWriter out;
59 private PrintWriter fileWriter;
60 private String detail;
63 private Transition transition;
65 // DPOR-related fields
67 private Integer[] choices;
68 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
69 private int choiceCounter;
70 private int maxEventChoice;
71 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
72 private HashSet<Integer> currVisitedStates; // States being visited in the current execution
73 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
74 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
75 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
76 // Data structure to analyze field Read/Write accesses and conflicts
77 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
78 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
79 private ArrayList<BacktrackPoint> backtrackPointList; // Record backtrack points (CG, state Id, and choice)
80 private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
81 private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
82 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
83 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
84 private HashMap<Integer, Integer> stateToChoiceCounterMap; // Maps state IDs to the choice counter
87 private boolean isBooleanCGFlipped;
88 private boolean isEndOfExecution;
91 private int numOfConflicts;
92 private int numOfTransitions;
94 public DPORStateReducer(Config config, JPF jpf) {
95 verboseMode = config.getBoolean("printout_state_transition", false);
96 stateReductionMode = config.getBoolean("activate_state_reduction", true);
98 out = new PrintWriter(System.out, true);
102 String outputFile = config.getString("file_output");
103 if (!outputFile.isEmpty()) {
105 fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
106 } catch (IOException e) {
109 isBooleanCGFlipped = false;
111 numOfTransitions = 0;
112 restorableStateMap = new HashMap<>();
113 initializeStatesVariables();
117 public void stateRestored(Search search) {
119 id = search.getStateId();
120 depth = search.getDepth();
121 transition = search.getTransition();
123 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
124 " and depth: " + depth + "\n");
129 public void searchStarted(Search search) {
131 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
136 public void stateAdvanced(Search search) {
138 id = search.getStateId();
139 depth = search.getDepth();
140 transition = search.getTransition();
141 if (search.isNewState()) {
147 if (search.isEndState()) {
148 out.println("\n==> DEBUG: This is the last state!\n");
151 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
152 " which is " + detail + " Transition: " + transition + "\n");
154 if (stateReductionMode) {
155 updateStateInfo(search);
160 public void stateBacktracked(Search search) {
162 id = search.getStateId();
163 depth = search.getDepth();
164 transition = search.getTransition();
167 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
168 " and depth: " + depth + "\n");
170 if (stateReductionMode) {
171 updateStateInfo(search);
175 static Logger log = JPF.getLogger("report");
178 public void searchFinished(Search search) {
179 if (stateReductionMode) {
180 // Number of conflicts = first trace + subsequent backtrack points
181 numOfConflicts += 1 + doneBacktrackSet.size();
184 out.println("\n==> DEBUG: ----------------------------------- search finished");
185 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
186 out.println("\n==> DEBUG: Number of conflicts : " + numOfConflicts);
187 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
188 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
190 fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
191 fileWriter.println("==> DEBUG: Number of conflicts : " + numOfConflicts);
192 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
193 fileWriter.println();
199 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
200 if (stateReductionMode) {
201 // Initialize with necessary information from the CG
202 if (nextCG instanceof IntChoiceFromSet) {
203 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
204 if (!isEndOfExecution) {
205 // Check if CG has been initialized, otherwise initialize it
206 Integer[] cgChoices = icsCG.getAllChoices();
207 // Record the events (from choices)
208 if (choices == null) {
210 // Make a copy of choices as reference
211 refChoices = copyChoices(choices);
212 // Record the max event choice (the last element of the choice array)
213 maxEventChoice = choices[choices.length - 1];
215 icsCG.setNewValues(choices);
217 // Use a modulo since choiceCounter is going to keep increasing
218 int choiceIndex = choiceCounter % choices.length;
219 icsCG.advance(choices[choiceIndex]);
221 // Set done all CGs while transitioning to a new execution
229 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
231 if (stateReductionMode) {
232 // Check the boolean CG and if it is flipped, we are resetting the analysis
233 if (currentCG instanceof BooleanChoiceGenerator) {
234 if (!isBooleanCGFlipped) {
235 isBooleanCGFlipped = true;
237 // Number of conflicts = first trace + subsequent backtrack points
238 numOfConflicts = 1 + doneBacktrackSet.size();
239 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
240 initializeStatesVariables();
243 // Check every choice generated and ensure fair scheduling!
244 if (currentCG instanceof IntChoiceFromSet) {
245 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
246 // If this is a new CG then we need to update data structures
247 resetStatesForNewExecution(icsCG, vm);
248 // If we don't see a fair scheduling of events/choices then we have to enforce it
249 fairSchedulingAndBacktrackPoint(icsCG, vm);
250 // Explore the next backtrack point:
251 // 1) if we have seen this state or this state contains cycles that involve all events, and
252 // 2) after the current CG is advanced at least once
253 if (terminateCurrentExecution() && choiceCounter > 0) {
254 exploreNextBacktrackPoints(vm, icsCG);
258 // Map state to event
259 mapStateToEvent(icsCG.getNextChoice());
260 justVisitedStates.clear();
269 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
270 if (stateReductionMode) {
271 if (!isEndOfExecution) {
272 // Has to be initialized and a integer CG
273 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
274 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
275 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
276 if (currentChoice < 0) { // If choice is -1 then skip
279 currentChoice = checkAndAdjustChoice(currentChoice, vm);
280 // Record accesses from executed instructions
281 if (executedInsn instanceof JVMFieldInstruction) {
282 // Analyze only after being initialized
283 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
284 // We don't care about libraries
285 if (!isFieldExcluded(fieldClass)) {
286 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
288 } else if (executedInsn instanceof INVOKEINTERFACE) {
289 // Handle the read/write accesses that occur through iterators
290 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
292 // Analyze conflicts from next instructions
293 if (nextInsn instanceof JVMFieldInstruction) {
294 // Skip the constructor because it is called once and does not have shared access with other objects
295 if (!nextInsn.getMethodInfo().getName().equals("<init>")) {
296 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
297 if (!isFieldExcluded(fieldClass)) {
298 // Check for conflict (go backward from current choice and get the first conflict)
299 for (int eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
300 // Check for conflicts with Write fields for both Read and Write instructions
301 // Check and record a backtrack set for just once!
302 if (isConflictFound(nextInsn, eventCounter, currentChoice, fieldClass) &&
303 isNewConflict(currentChoice, eventCounter)) {
304 createBacktrackingPoint(currentChoice, eventCounter);
320 // This class compactly stores Read and Write field sets
321 // We store the field name and its object ID
322 // Sharing the same field means the same field name and object ID
323 private class ReadWriteSet {
324 private HashMap<String, Integer> readSet;
325 private HashMap<String, Integer> writeSet;
327 public ReadWriteSet() {
328 readSet = new HashMap<>();
329 writeSet = new HashMap<>();
332 public void addReadField(String field, int objectId) {
333 readSet.put(field, objectId);
336 public void addWriteField(String field, int objectId) {
337 writeSet.put(field, objectId);
340 public Set<String> getReadSet() {
341 return readSet.keySet();
344 public Set<String> getWriteSet() {
345 return writeSet.keySet();
348 public boolean readFieldExists(String field) {
349 return readSet.containsKey(field);
352 public boolean writeFieldExists(String field) {
353 return writeSet.containsKey(field);
356 public int readFieldObjectId(String field) {
357 return readSet.get(field);
360 public int writeFieldObjectId(String field) {
361 return writeSet.get(field);
365 // This class compactly stores backtrack points: 1) backtrack state ID, and 2) backtracking choices
366 private class BacktrackPoint {
367 private IntChoiceFromSet backtrackCG; // CG at this backtrack point
368 private int stateId; // State at this backtrack point
369 private int choice; // Choice chosen at this backtrack point
371 public BacktrackPoint(IntChoiceFromSet cg, int stId, int cho) {
377 public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
379 public int getStateId() {
383 public int getChoice() {
389 private final static String DO_CALL_METHOD = "doCall";
390 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
391 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
392 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
393 // Groovy library created fields
394 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
396 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
397 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
398 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
399 // Java and Groovy libraries
400 { "java", "org", "sun", "com", "gov", "groovy"};
401 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
402 private final static String GET_PROPERTY_METHOD =
403 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
404 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
405 private final static String JAVA_INTEGER = "int";
406 private final static String JAVA_STRING_LIB = "java.lang.String";
409 private void fairSchedulingAndBacktrackPoint(IntChoiceFromSet icsCG, VM vm) {
410 // Check the next choice and if the value is not the same as the expected then force the expected value
411 int choiceIndex = choiceCounter % refChoices.length;
412 int nextChoice = icsCG.getNextChoice();
413 if (refChoices[choiceIndex] != nextChoice) {
414 int expectedChoice = refChoices[choiceIndex];
415 int currCGIndex = icsCG.getNextChoiceIndex();
416 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
417 icsCG.setChoice(currCGIndex, expectedChoice);
420 // Record state ID and choice/event as backtrack point
421 int stateId = vm.getStateId();
422 backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex]));
423 // Store restorable state object for this state (always store the latest)
424 RestorableVMState restorableState = vm.getRestorableState();
425 restorableStateMap.put(stateId, restorableState);
428 private Integer[] copyChoices(Integer[] choicesToCopy) {
430 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
431 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
432 return copyOfChoices;
435 // --- Functions related to cycle detection
437 // Detect cycles in the current execution/trace
438 // We terminate the execution iff:
439 // (1) the state has been visited in the current execution
440 // (2) the state has one or more cycles that involve all the events
441 // With simple approach we only need to check for a re-visited state.
442 // Basically, we have to check that we have executed all events between two occurrences of such state.
443 private boolean containsCyclesWithAllEvents(int stId) {
445 // False if the state ID hasn't been recorded
446 if (!stateToEventMap.containsKey(stId)) {
449 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
450 // Check if this set contains all the event choices
451 // If not then this is not the terminating condition
452 for(int i=0; i<=maxEventChoice; i++) {
453 if (!visitedEvents.contains(i)) {
460 private void initializeStatesVariables() {
467 currVisitedStates = new HashSet<>();
468 justVisitedStates = new HashSet<>();
469 prevVisitedStates = new HashSet<>();
470 stateToEventMap = new HashMap<>();
472 backtrackMap = new HashMap<>();
473 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
474 backtrackPointList = new ArrayList<>();
475 conflictPairMap = new HashMap<>();
476 doneBacktrackSet = new HashSet<>();
477 readWriteFieldsMap = new HashMap<>();
478 stateToChoiceCounterMap = new HashMap<>();
480 isEndOfExecution = false;
483 private void mapStateToEvent(int nextChoiceValue) {
484 // Update all states with this event/choice
485 // This means that all past states now see this transition
486 Set<Integer> stateSet = stateToEventMap.keySet();
487 for(Integer stateId : stateSet) {
488 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
489 eventSet.add(nextChoiceValue);
493 private boolean terminateCurrentExecution() {
494 // We need to check all the states that have just been visited
495 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
496 for(Integer stateId : justVisitedStates) {
497 if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
504 private void updateStateInfo(Search search) {
505 // Update the state variables
506 // Line 19 in the paper page 11 (see the heading note above)
507 int stateId = search.getStateId();
508 // Insert state ID into the map if it is new
509 if (!stateToEventMap.containsKey(stateId)) {
510 HashSet<Integer> eventSet = new HashSet<>();
511 stateToEventMap.put(stateId, eventSet);
513 stateToChoiceCounterMap.put(stateId, choiceCounter);
514 analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
515 justVisitedStates.add(stateId);
516 currVisitedStates.add(stateId);
519 // --- Functions related to Read/Write access analysis on shared fields
521 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList) {
522 // Insert backtrack point to the right state ID
523 LinkedList<Integer[]> backtrackList;
524 if (backtrackMap.containsKey(stateId)) {
525 backtrackList = backtrackMap.get(stateId);
527 backtrackList = new LinkedList<>();
528 backtrackMap.put(stateId, backtrackList);
530 backtrackList.addFirst(newChoiceList);
531 // Add to priority queue
532 if (!backtrackStateQ.contains(stateId)) {
533 backtrackStateQ.add(stateId);
537 // Analyze Read/Write accesses that are directly invoked on fields
538 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
539 // Do the analysis to get Read and Write accesses to fields
540 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
541 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
542 // Record the field in the map
543 if (executedInsn instanceof WriteInstruction) {
544 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
545 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
546 if (fieldClass.startsWith(str)) {
550 rwSet.addWriteField(fieldClass, objectId);
551 } else if (executedInsn instanceof ReadInstruction) {
552 rwSet.addReadField(fieldClass, objectId);
556 // Analyze Read accesses that are indirect (performed through iterators)
557 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
558 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
560 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
561 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
562 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
563 // Extract info from the stack frame
564 StackFrame frame = ti.getTopFrame();
565 int[] frameSlots = frame.getSlots();
566 // Get the Groovy callsite library at index 0
567 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
568 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
571 // Get the iterated object whose property is accessed
572 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
573 if (eiAccessObj == null) {
576 // We exclude library classes (they start with java, org, etc.) and some more
577 String objClassName = eiAccessObj.getClassInfo().getName();
578 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
579 excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName)) {
582 // Extract fields from this object and put them into the read write
583 int numOfFields = eiAccessObj.getNumberOfFields();
584 for(int i=0; i<numOfFields; i++) {
585 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
586 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
587 String fieldClass = fieldInfo.getFullName();
588 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
589 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
590 // Record the field in the map
591 rwSet.addReadField(fieldClass, objectId);
597 private int checkAndAdjustChoice(int currentChoice, VM vm) {
598 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
599 // for certain method calls in the infrastructure, e.g., eventSince()
600 int currChoiceInd = currentChoice % refChoices.length;
601 int currChoiceFromCG = currChoiceInd;
602 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
603 // This is the main event CG
604 if (currentCG instanceof IntIntervalGenerator) {
605 // This is the interval CG used in device handlers
606 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
607 // Iterate until we find the IntChoiceFromSet CG
608 while (!(parentCG instanceof IntChoiceFromSet)) {
609 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
611 int actualEvtNum = ((IntChoiceFromSet) parentCG).getNextChoice();
612 // Find the index of the event/choice in refChoices
613 for (int i = 0; i<refChoices.length; i++) {
614 if (actualEvtNum == refChoices[i]) {
615 currChoiceFromCG = i;
620 if (currChoiceInd != currChoiceFromCG) {
621 currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
623 return currentChoice;
626 private void createBacktrackingPoint(int currentChoice, int confEvtNum) {
628 // Create a new list of choices for backtrack based on the current choice and conflicting event number
629 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
630 // for the original set {0, 1, 2, 3}
631 Integer[] newChoiceList = new Integer[refChoices.length];
632 // Put the conflicting event numbers first and reverse the order
633 int actualCurrCho = currentChoice % refChoices.length;
634 // We use the actual choices here in case they have been modified/adjusted by the fair scheduling method
635 newChoiceList[0] = choices[actualCurrCho];
636 newChoiceList[1] = backtrackPointList.get(confEvtNum).getChoice();
637 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
638 for (int i = 0, j = 2; i < refChoices.length; i++) {
639 if (refChoices[i] != newChoiceList[0] && refChoices[i] != newChoiceList[1]) {
640 newChoiceList[j] = refChoices[i];
644 // Get the backtrack CG for this backtrack point
645 int stateId = backtrackPointList.get(confEvtNum).getStateId();
646 // Check if this trace has been done starting from this state
647 if (isTraceAlreadyConstructed(newChoiceList, stateId)) {
650 addNewBacktrackPoint(stateId, newChoiceList);
653 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
654 for (String excludedField : excludedStrings) {
655 if (className.contains(excludedField)) {
662 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
663 for (String excludedField : excludedStrings) {
664 if (className.endsWith(excludedField)) {
671 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
672 for (String excludedField : excludedStrings) {
673 if (className.startsWith(excludedField)) {
680 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
682 // Check if we are reaching the end of our execution: no more backtracking points to explore
683 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
684 if (!backtrackStateQ.isEmpty()) {
685 // Set done all the other backtrack points
686 for (BacktrackPoint backtrackPoint : backtrackPointList) {
687 backtrackPoint.getBacktrackCG().setDone();
689 // Reset the next backtrack point with the latest state
690 int hiStateId = backtrackStateQ.peek();
691 // Restore the state first if necessary
692 if (vm.getStateId() != hiStateId) {
693 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
694 vm.restoreState(restorableState);
696 // Set the backtrack CG
697 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
698 setBacktrackCG(hiStateId, backtrackCG);
700 // Set done this last CG (we save a few rounds)
703 // Save all the visited states when starting a new execution of trace
704 prevVisitedStates.addAll(currVisitedStates);
705 currVisitedStates.clear();
706 // This marks a transitional period to the new CG
707 isEndOfExecution = true;
710 private ReadWriteSet getReadWriteSet(int currentChoice) {
711 // Do the analysis to get Read and Write accesses to fields
713 // We already have an entry
714 if (readWriteFieldsMap.containsKey(currentChoice)) {
715 rwSet = readWriteFieldsMap.get(currentChoice);
716 } else { // We need to create a new entry
717 rwSet = new ReadWriteSet();
718 readWriteFieldsMap.put(currentChoice, rwSet);
723 private boolean isConflictFound(int eventCounter, int currentChoice) {
725 int actualCurrCho = currentChoice % refChoices.length;
726 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
727 if (!readWriteFieldsMap.containsKey(eventCounter) ||
728 choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
732 ReadWriteSet currRWSet = readWriteFieldsMap.get(currentChoice);
733 // R/W set of choice/event that may have a potential conflict
734 ReadWriteSet evtRWSet = readWriteFieldsMap.get(eventCounter);
735 // Check for conflicts with Read and Write fields for Write instructions
736 Set<String> currWriteSet = currRWSet.getWriteSet();
737 for(String writeField : currWriteSet) {
738 int currObjId = currRWSet.writeFieldObjectId(writeField);
739 if ((evtRWSet.readFieldExists(writeField) && evtRWSet.readFieldObjectId(writeField) == currObjId) ||
740 (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId)) {
744 // Check for conflicts with Write fields for Read instructions
745 Set<String> currReadSet = currRWSet.getReadSet();
746 for(String readField : currReadSet) {
747 int currObjId = currRWSet.readFieldObjectId(readField);
748 if (evtRWSet.writeFieldExists(readField) && evtRWSet.writeFieldObjectId(readField) == currObjId) {
752 // Return false if no conflict is found
756 private boolean isConflictFound(Instruction nextInsn, int eventCounter, int currentChoice, String fieldClass) {
758 int actualCurrCho = currentChoice % refChoices.length;
759 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
760 if (!readWriteFieldsMap.containsKey(eventCounter) ||
761 choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
764 ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
765 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
766 // Check for conflicts with Write fields for both Read and Write instructions
767 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
768 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
769 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
770 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
776 private boolean isFieldExcluded(String field) {
777 // Check against "starts-with", "ends-with", and "contains" list
778 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
779 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
780 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
787 private boolean isNewConflict(int currentEvent, int eventNumber) {
788 HashSet<Integer> conflictSet;
789 if (!conflictPairMap.containsKey(currentEvent)) {
790 conflictSet = new HashSet<>();
791 conflictPairMap.put(currentEvent, conflictSet);
793 conflictSet = conflictPairMap.get(currentEvent);
795 // If this conflict has been recorded before, we return false because
796 // we don't want to save this backtrack point twice
797 if (conflictSet.contains(eventNumber)) {
800 // If it hasn't been recorded, then do otherwise
801 conflictSet.add(eventNumber);
805 private boolean isTraceAlreadyConstructed(Integer[] choiceList, int stateId) {
806 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
807 // TODO: THIS IS AN OPTIMIZATION!
808 // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
809 // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
810 // The second time this event 1 is explored, it will generate the same state as the first one
811 StringBuilder sb = new StringBuilder();
814 sb.append(choiceList[0]);
815 // Check if the trace has been constructed as a backtrack point for this state
816 if (doneBacktrackSet.contains(sb.toString())) {
819 doneBacktrackSet.add(sb.toString());
823 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
824 if (choices == null || choices != icsCG.getAllChoices()) {
825 // Reset state variables
827 choices = icsCG.getAllChoices();
828 refChoices = copyChoices(choices);
829 // Clearing data structures
830 conflictPairMap.clear();
831 readWriteFieldsMap.clear();
832 stateToEventMap.clear();
833 isEndOfExecution = false;
834 backtrackPointList.clear();
838 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
839 // Set a backtrack CG based on a state ID
840 LinkedList<Integer[]> backtrackChoices = backtrackMap.get(stateId);
841 backtrackCG.setNewValues(backtrackChoices.removeLast()); // Get the last from the queue
842 backtrackCG.setStateId(stateId);
844 // Remove from the queue if we don't have more backtrack points for that state
845 if (backtrackChoices.isEmpty()) {
846 backtrackMap.remove(stateId);
847 backtrackStateQ.remove(stateId);
851 // --- Functions related to the reachability analysis when there is a state match
853 // We use backtrackPointsList to analyze the reachable states/events when there is a state match:
854 // 1) Whenever there is state match, there is a cycle of events
855 // 2) We need to analyze and find conflicts for the reachable choices/events in the cycle
856 // 3) Then we create a new backtrack point for every new conflict
857 private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
858 // Perform this analysis only when:
859 // 1) there is a state match,
860 // 2) this is not during a switch to a new execution,
861 // 3) at least 2 choices/events have been explored (choiceCounter > 1),
862 // 4) the matched state has been encountered in the current execution, and
863 // 5) state > 0 (state 0 is for boolean CG)
864 if (!vm.isNewState() && !isEndOfExecution && choiceCounter > 1 &&
865 currVisitedStates.contains(stateId) && (stateId > 0)) {
866 // Find the choice/event that marks the start of this cycle: first choice we explore for conflicts
867 int conflictChoice = stateToChoiceCounterMap.get(stateId);
868 int currentChoice = choiceCounter - 1;
869 // Find conflicts between choices/events in this cycle (we scan forward in the cycle, not backward)
870 while (conflictChoice < currentChoice) {
871 for (int eventCounter = conflictChoice + 1; eventCounter <= currentChoice; eventCounter++) {
872 if (isConflictFound(eventCounter, conflictChoice) && isNewConflict(conflictChoice, eventCounter)) {
873 createBacktrackingPoint(conflictChoice, eventCounter);