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.jvm.bytecode.INVOKEINTERFACE;
24 import gov.nasa.jpf.jvm.bytecode.JVMFieldInstruction;
25 import gov.nasa.jpf.search.Search;
26 import gov.nasa.jpf.vm.*;
27 import gov.nasa.jpf.vm.bytecode.ReadInstruction;
28 import gov.nasa.jpf.vm.bytecode.WriteInstruction;
29 import gov.nasa.jpf.vm.choice.IntChoiceFromSet;
30 import gov.nasa.jpf.vm.choice.IntIntervalGenerator;
32 import java.io.FileWriter;
33 import java.io.IOException;
34 import java.io.PrintWriter;
36 import java.util.logging.Logger;
39 * This a DPOR implementation for event-driven applications with loops that create cycles of state matching
40 * In this new DPOR algorithm/implementation, each run is terminated iff:
41 * - we find a state that matches a state in a previous run, or
42 * - we have a matched state in the current run that consists of cycles that contain all choices/events.
44 public class DPORStateReducerEfficient extends ListenerAdapter {
46 // Information printout fields for verbose mode
47 private boolean verboseMode;
48 private boolean stateReductionMode;
49 private final PrintWriter out;
50 private PrintWriter fileWriter;
51 private String detail;
54 private Transition transition;
56 // DPOR-related fields
58 private Integer[] choices;
59 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
60 private int choiceCounter;
61 private int maxEventChoice;
62 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
63 private HashSet<Integer> currVisitedStates; // States being visited in the current execution
64 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
65 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
66 private HashSet<ClassInfo> nonRelevantClasses;// Class info objects of non-relevant classes
67 private HashSet<FieldInfo> nonRelevantFields; // Field info objects of non-relevant fields
68 private HashSet<FieldInfo> relevantFields; // Field info objects of relevant fields
69 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
70 // Data structure to analyze field Read/Write accesses and conflicts
71 private HashMap<Integer, LinkedList<BacktrackExecution>> backtrackMap; // Track created backtracking points
72 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
73 private Execution currentExecution; // Holds the information about the current execution
74 private HashMap<Integer, HashSet<Integer>> doneBacktrackMap; // Record state ID and trace already constructed
75 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
76 private RGraph rGraph; // R-Graph for past executions
79 private boolean isBooleanCGFlipped;
80 private boolean isEndOfExecution;
83 private int numOfTransitions;
85 public DPORStateReducerEfficient(Config config, JPF jpf) {
86 verboseMode = config.getBoolean("printout_state_transition", false);
87 stateReductionMode = config.getBoolean("activate_state_reduction", true);
89 out = new PrintWriter(System.out, true);
93 String outputFile = config.getString("file_output");
94 if (!outputFile.isEmpty()) {
96 fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
97 } catch (IOException e) {
100 isBooleanCGFlipped = false;
101 numOfTransitions = 0;
102 nonRelevantClasses = new HashSet<>();
103 nonRelevantFields = new HashSet<>();
104 relevantFields = new HashSet<>();
105 restorableStateMap = new HashMap<>();
106 initializeStatesVariables();
110 public void stateRestored(Search search) {
112 id = search.getStateId();
113 depth = search.getDepth();
114 transition = search.getTransition();
116 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
117 " and depth: " + depth + "\n");
122 public void searchStarted(Search search) {
124 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
129 public void stateAdvanced(Search search) {
131 id = search.getStateId();
132 depth = search.getDepth();
133 transition = search.getTransition();
134 if (search.isNewState()) {
140 if (search.isEndState()) {
141 out.println("\n==> DEBUG: This is the last state!\n");
144 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
145 " which is " + detail + " Transition: " + transition + "\n");
147 if (stateReductionMode) {
148 updateStateInfo(search);
153 public void stateBacktracked(Search search) {
155 id = search.getStateId();
156 depth = search.getDepth();
157 transition = search.getTransition();
160 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
161 " and depth: " + depth + "\n");
163 if (stateReductionMode) {
164 updateStateInfo(search);
168 static Logger log = JPF.getLogger("report");
171 public void searchFinished(Search search) {
173 out.println("\n==> DEBUG: ----------------------------------- search finished");
174 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
175 out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
176 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
178 fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
179 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
180 fileWriter.println();
186 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
187 if (stateReductionMode) {
188 // Initialize with necessary information from the CG
189 if (nextCG instanceof IntChoiceFromSet) {
190 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
191 // Tell JPF that we are performing DPOR
193 if (!isEndOfExecution) {
194 // Check if CG has been initialized, otherwise initialize it
195 Integer[] cgChoices = icsCG.getAllChoices();
196 // Record the events (from choices)
197 if (choices == null) {
199 // Make a copy of choices as reference
200 refChoices = copyChoices(choices);
201 // Record the max event choice (the last element of the choice array)
202 maxEventChoice = choices[choices.length - 1];
204 icsCG.setNewValues(choices);
206 // Use a modulo since choiceCounter is going to keep increasing
207 int choiceIndex = choiceCounter % choices.length;
208 icsCG.advance(choices[choiceIndex]);
210 // Set done all CGs while transitioning to a new execution
218 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
219 if (stateReductionMode) {
220 // Check the boolean CG and if it is flipped, we are resetting the analysis
221 if (currentCG instanceof BooleanChoiceGenerator) {
222 if (!isBooleanCGFlipped) {
223 isBooleanCGFlipped = true;
225 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
226 initializeStatesVariables();
229 // Check every choice generated and ensure fair scheduling!
230 if (currentCG instanceof IntChoiceFromSet) {
231 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
232 // If this is a new CG then we need to update data structures
233 resetStatesForNewExecution(icsCG, vm);
234 // If we don't see a fair scheduling of events/choices then we have to enforce it
235 ensureFairSchedulingAndSetupTransition(icsCG, vm);
236 // Update backtrack set of an executed event (transition): one transition before this one
237 updateBacktrackSet(currentExecution, choiceCounter - 1);
238 // Explore the next backtrack point:
239 // 1) if we have seen this state or this state contains cycles that involve all events, and
240 // 2) after the current CG is advanced at least once
241 if (terminateCurrentExecution() && choiceCounter > 0) {
242 exploreNextBacktrackPoints(vm, icsCG);
246 // Map state to event
247 mapStateToEvent(icsCG.getNextChoice());
248 justVisitedStates.clear();
257 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
258 if (stateReductionMode) {
259 if (!isEndOfExecution) {
260 // Has to be initialized and a integer CG
261 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
262 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
263 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
264 if (currentChoice < 0) { // If choice is -1 then skip
267 currentChoice = checkAndAdjustChoice(currentChoice, vm);
268 // Record accesses from executed instructions
269 if (executedInsn instanceof JVMFieldInstruction) {
270 // We don't care about libraries
271 if (!isFieldExcluded(executedInsn)) {
272 analyzeReadWriteAccesses(executedInsn, currentChoice);
274 } else if (executedInsn instanceof INVOKEINTERFACE) {
275 // Handle the read/write accesses that occur through iterators
276 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
288 // This class compactly stores backtrack execution:
289 // 1) backtrack choice list, and
290 // 2) first backtrack point (linking with predecessor execution)
291 private class BacktrackExecution {
292 private Integer[] choiceList;
293 private TransitionEvent firstTransition;
295 public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
296 choiceList = choList;
297 firstTransition = fTransition;
300 public Integer[] getChoiceList() {
304 public TransitionEvent getFirstTransition() {
305 return firstTransition;
309 // This class stores a representation of an execution
310 // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
311 // TODO: We basically need to keep track of:
312 // TODO: (1) last read/write access to each memory location
313 // TODO: (2) last state with two or more incoming events/transitions
314 private class Execution {
315 private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
316 private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
317 private boolean isNew; // Track if this is the first time it is accessed
318 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
321 cgToChoiceMap = new HashMap<>();
322 executionTrace = new ArrayList<>();
324 readWriteFieldsMap = new HashMap<>();
327 public void addTransition(TransitionEvent newBacktrackPoint) {
328 executionTrace.add(newBacktrackPoint);
331 public void clearCGToChoiceMap() {
332 cgToChoiceMap = null;
335 public int getChoiceFromCG(IntChoiceFromSet icsCG) {
336 return cgToChoiceMap.get(icsCG);
339 public ArrayList<TransitionEvent> getExecutionTrace() {
340 return executionTrace;
343 public TransitionEvent getFirstTransition() {
344 return executionTrace.get(0);
347 public TransitionEvent getLastTransition() {
348 return executionTrace.get(executionTrace.size() - 1);
351 public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
352 return readWriteFieldsMap;
355 public boolean isNew() {
357 // Right after this is accessed, it is no longer new
364 public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
365 cgToChoiceMap.put(icsCG, choice);
369 // This class compactly stores a predecessor
370 // 1) a predecessor execution
371 // 2) the predecessor choice in that predecessor execution
372 private class Predecessor {
373 private int choice; // Predecessor choice
374 private Execution execution; // Predecessor execution
376 public Predecessor(Execution predExec, int predChoice) {
378 execution = predExec;
381 public int getChoice() {
385 public Execution getExecution() {
390 // This class represents a R-Graph (in the paper it is a state transition graph R)
391 // This implementation stores reachable transitions from and connects with past executions
392 private class RGraph {
393 private int hiStateId; // Maximum state Id
394 private HashMap<Integer, HashSet<TransitionEvent>> graph; // Reachable transitions from past executions
398 graph = new HashMap<>();
401 public void addReachableTransition(int stateId, TransitionEvent transition) {
402 // Record transition into graph
403 HashSet<TransitionEvent> transitionSet;
404 if (graph.containsKey(stateId)) {
405 transitionSet = graph.get(stateId);
407 transitionSet = new HashSet<>();
408 graph.put(stateId, transitionSet);
410 // Insert into the set if it does not contain it yet
411 if (!transitionSet.contains(transition)) {
412 transitionSet.add(transition);
414 // Update highest state ID
415 if (hiStateId < stateId) {
420 public HashSet<TransitionEvent> getReachableTransitionsAtState(int stateId) {
421 if (!graph.containsKey(stateId)) {
422 // This is a loop from a transition to itself, so just return the current transition
423 HashSet<TransitionEvent> transitionSet = new HashSet<>();
424 transitionSet.add(currentExecution.getLastTransition());
425 return transitionSet;
427 return graph.get(stateId);
431 // This class compactly stores Read and Write field sets
432 // We store the field name and its object ID
433 // Sharing the same field means the same field name and object ID
434 private class ReadWriteSet {
435 private HashMap<String, Integer> readMap;
436 private HashMap<String, Integer> writeMap;
438 public ReadWriteSet() {
439 readMap = new HashMap<>();
440 writeMap = new HashMap<>();
443 public void addReadField(String field, int objectId) {
444 readMap.put(field, objectId);
447 public void addWriteField(String field, int objectId) {
448 writeMap.put(field, objectId);
451 public void removeReadField(String field) {
452 readMap.remove(field);
455 public void removeWriteField(String field) {
456 writeMap.remove(field);
459 public boolean isEmpty() {
460 return readMap.isEmpty() && writeMap.isEmpty();
463 public ReadWriteSet getCopy() {
464 ReadWriteSet copyRWSet = new ReadWriteSet();
465 // Copy the maps in the set into the new object copy
466 copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
467 copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
471 public Set<String> getReadSet() {
472 return readMap.keySet();
475 public Set<String> getWriteSet() {
476 return writeMap.keySet();
479 public boolean readFieldExists(String field) {
480 return readMap.containsKey(field);
483 public boolean writeFieldExists(String field) {
484 return writeMap.containsKey(field);
487 public int readFieldObjectId(String field) {
488 return readMap.get(field);
491 public int writeFieldObjectId(String field) {
492 return writeMap.get(field);
495 private HashMap<String, Integer> getReadMap() {
499 private HashMap<String, Integer> getWriteMap() {
503 private void setReadMap(HashMap<String, Integer> rMap) {
507 private void setWriteMap(HashMap<String, Integer> wMap) {
512 // This class provides a data structure to store TransitionEvent and ReadWriteSet for a summary
513 private class SummaryNode {
514 private TransitionEvent transitionEvent;
515 private ReadWriteSet readWriteSet;
517 public SummaryNode(TransitionEvent transEvent, ReadWriteSet rwSet) {
518 transitionEvent = transEvent;
519 readWriteSet = rwSet;
522 public TransitionEvent getTransitionEvent() {
523 return transitionEvent;
526 public ReadWriteSet getReadWriteSet() {
531 // This class compactly stores transitions:
535 // 4) predecessors (for backward DFS).
536 private class TransitionEvent {
537 private int choice; // Choice chosen at this transition
538 private int choiceCounter; // Choice counter at this transition
539 private Execution execution; // The execution where this transition belongs
540 private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
541 private HashMap<Integer, SummaryNode> transitionSummary;
542 // Summary of pushed transitions at the current transition
543 private HashMap<Execution, HashSet<Integer>> recordedPredecessors;
544 // Memorize event and choice number to not record them twice
545 private int stateId; // State at this transition
546 private IntChoiceFromSet transitionCG; // CG at this transition
548 public TransitionEvent() {
552 predecessors = new HashSet<>();
553 transitionSummary = new HashMap<>();
554 recordedPredecessors = new HashMap<>();
559 public int getChoice() {
563 public int getChoiceCounter() {
564 return choiceCounter;
567 public Execution getExecution() {
571 public HashSet<Predecessor> getPredecessors() {
575 public int getStateId() {
579 public HashMap<Integer, SummaryNode> getTransitionSummary() {
580 return transitionSummary;
583 public IntChoiceFromSet getTransitionCG() { return transitionCG; }
585 private boolean isRecordedPredecessor(Execution execution, int choice) {
586 // See if we have recorded this predecessor earlier
587 HashSet<Integer> recordedChoices;
588 if (recordedPredecessors.containsKey(execution)) {
589 recordedChoices = recordedPredecessors.get(execution);
590 if (recordedChoices.contains(choice)) {
594 recordedChoices = new HashSet<>();
595 recordedPredecessors.put(execution, recordedChoices);
597 // Record the choice if we haven't seen it
598 recordedChoices.add(choice);
603 private ReadWriteSet performUnion(ReadWriteSet recordedRWSet, ReadWriteSet rwSet) {
604 // Combine the same write accesses and record in the recordedRWSet
605 HashMap<String, Integer> recordedWriteMap = recordedRWSet.getWriteMap();
606 HashMap<String, Integer> writeMap = rwSet.getWriteMap();
607 for(Map.Entry<String, Integer> entry : recordedWriteMap.entrySet()) {
608 String writeField = entry.getKey();
609 // Remove the entry from rwSet if both field and object ID are the same
610 if (writeMap.containsKey(writeField) &&
611 (writeMap.get(writeField).equals(recordedWriteMap.get(writeField)))) {
612 writeMap.remove(writeField);
615 // Then add everything into the recorded map because these will be traversed
616 recordedWriteMap.putAll(writeMap);
617 // Combine the same read accesses and record in the recordedRWSet
618 HashMap<String, Integer> recordedReadMap = recordedRWSet.getReadMap();
619 HashMap<String, Integer> readMap = rwSet.getReadMap();
620 for(Map.Entry<String, Integer> entry : recordedReadMap.entrySet()) {
621 String readField = entry.getKey();
622 // Remove the entry from rwSet if both field and object ID are the same
623 if (readMap.containsKey(readField) &&
624 (readMap.get(readField).equals(recordedReadMap.get(readField)))) {
625 readMap.remove(readField);
628 // Then add everything into the recorded map because these will be traversed
629 recordedReadMap.putAll(readMap);
634 public void recordPredecessor(Execution execution, int choice) {
635 if (!isRecordedPredecessor(execution, choice)) {
636 predecessors.add(new Predecessor(execution, choice));
640 public ReadWriteSet recordTransitionSummary(TransitionEvent transition, ReadWriteSet rwSet, boolean refresh) {
641 // Record transition into reachability summary
642 // TransitionMap maps event (choice) number to a R/W set
643 int choice = transition.getChoice();
644 SummaryNode summaryNode;
645 // Insert transition into the map if we haven't had this event number recorded
646 if (!transitionSummary.containsKey(choice) || refresh) {
647 summaryNode = new SummaryNode(transition, rwSet.getCopy());
648 transitionSummary.put(choice, summaryNode);
650 summaryNode = transitionSummary.get(choice);
651 // Perform union and subtraction between the recorded and the given R/W sets
652 rwSet = performUnion(summaryNode.getReadWriteSet(), rwSet);
657 public void setChoice(int cho) {
661 public void setChoiceCounter(int choCounter) {
662 choiceCounter = choCounter;
665 public void setExecution(Execution exec) {
669 public void setPredecessors(HashSet<Predecessor> preds) {
670 predecessors = new HashSet<>(preds);
673 public void setStateId(int stId) {
677 public void setTransitionCG(IntChoiceFromSet cg) {
683 private final static String DO_CALL_METHOD = "doCall";
684 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
685 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
686 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
687 // Groovy library created fields
688 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
690 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
691 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
692 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
693 // Java and Groovy libraries
694 { "java", "org", "sun", "com", "gov", "groovy"};
695 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
696 private final static String GET_PROPERTY_METHOD =
697 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
698 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
699 private final static String JAVA_INTEGER = "int";
700 private final static String JAVA_STRING_LIB = "java.lang.String";
703 private Integer[] copyChoices(Integer[] choicesToCopy) {
705 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
706 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
707 return copyOfChoices;
710 private void ensureFairSchedulingAndSetupTransition(IntChoiceFromSet icsCG, VM vm) {
711 // Check the next choice and if the value is not the same as the expected then force the expected value
712 int choiceIndex = choiceCounter % refChoices.length;
713 int nextChoice = icsCG.getNextChoice();
714 if (refChoices[choiceIndex] != nextChoice) {
715 int expectedChoice = refChoices[choiceIndex];
716 int currCGIndex = icsCG.getNextChoiceIndex();
717 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
718 icsCG.setChoice(currCGIndex, expectedChoice);
721 // Get state ID and associate it with this transition
722 int stateId = vm.getStateId();
723 TransitionEvent transition = setupTransition(icsCG, stateId, choiceIndex);
724 // Add new transition to the current execution and map it in R-Graph
725 for (Integer stId : justVisitedStates) { // Map this transition to all the previously passed states
726 rGraph.addReachableTransition(stId, transition);
728 currentExecution.mapCGToChoice(icsCG, choiceCounter);
729 // Store restorable state object for this state (always store the latest)
730 if (!restorableStateMap.containsKey(stateId)) {
731 RestorableVMState restorableState = vm.getRestorableState();
732 restorableStateMap.put(stateId, restorableState);
736 private TransitionEvent setupTransition(IntChoiceFromSet icsCG, int stateId, int choiceIndex) {
737 // Get a new transition
738 TransitionEvent transition;
739 if (currentExecution.isNew()) {
740 // We need to handle the first transition differently because this has a predecessor execution
741 transition = currentExecution.getFirstTransition();
743 transition = new TransitionEvent();
744 currentExecution.addTransition(transition);
745 transition.recordPredecessor(currentExecution, choiceCounter - 1);
747 transition.setExecution(currentExecution);
748 transition.setTransitionCG(icsCG);
749 transition.setStateId(stateId);
750 transition.setChoice(refChoices[choiceIndex]);
751 transition.setChoiceCounter(choiceCounter);
756 // --- Functions related to cycle detection and reachability graph
758 // Detect cycles in the current execution/trace
759 // We terminate the execution iff:
760 // (1) the state has been visited in the current execution
761 // (2) the state has one or more cycles that involve all the events
762 // With simple approach we only need to check for a re-visited state.
763 // Basically, we have to check that we have executed all events between two occurrences of such state.
764 private boolean completeFullCycle(int stId) {
765 // False if the state ID hasn't been recorded
766 if (!stateToEventMap.containsKey(stId)) {
769 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
770 // Check if this set contains all the event choices
771 // If not then this is not the terminating condition
772 for(int i=0; i<=maxEventChoice; i++) {
773 if (!visitedEvents.contains(i)) {
780 private void initializeStatesVariables() {
787 currVisitedStates = new HashSet<>();
788 justVisitedStates = new HashSet<>();
789 prevVisitedStates = new HashSet<>();
790 stateToEventMap = new HashMap<>();
792 backtrackMap = new HashMap<>();
793 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
794 currentExecution = new Execution();
795 currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
796 doneBacktrackMap = new HashMap<>();
797 rGraph = new RGraph();
799 isEndOfExecution = false;
802 private void mapStateToEvent(int nextChoiceValue) {
803 // Update all states with this event/choice
804 // This means that all past states now see this transition
805 Set<Integer> stateSet = stateToEventMap.keySet();
806 for(Integer stateId : stateSet) {
807 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
808 eventSet.add(nextChoiceValue);
812 private boolean terminateCurrentExecution() {
813 // We need to check all the states that have just been visited
814 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
815 for(Integer stateId : justVisitedStates) {
816 if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
823 private void updateStateInfo(Search search) {
824 // Update the state variables
825 int stateId = search.getStateId();
826 // Insert state ID into the map if it is new
827 if (!stateToEventMap.containsKey(stateId)) {
828 HashSet<Integer> eventSet = new HashSet<>();
829 stateToEventMap.put(stateId, eventSet);
831 analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
832 justVisitedStates.add(stateId);
833 if (!prevVisitedStates.contains(stateId)) {
834 // It is a currently visited states if the state has not been seen in previous executions
835 currVisitedStates.add(stateId);
839 // --- Functions related to Read/Write access analysis on shared fields
841 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList, TransitionEvent conflictTransition) {
842 // Insert backtrack point to the right state ID
843 LinkedList<BacktrackExecution> backtrackExecList;
844 if (backtrackMap.containsKey(stateId)) {
845 backtrackExecList = backtrackMap.get(stateId);
847 backtrackExecList = new LinkedList<>();
848 backtrackMap.put(stateId, backtrackExecList);
850 // Add the new backtrack execution object
851 TransitionEvent backtrackTransition = new TransitionEvent();
852 backtrackTransition.setPredecessors(conflictTransition.getPredecessors());
853 backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
854 // Add to priority queue
855 if (!backtrackStateQ.contains(stateId)) {
856 backtrackStateQ.add(stateId);
860 // Analyze Read/Write accesses that are directly invoked on fields
861 private void analyzeReadWriteAccesses(Instruction executedInsn, int currentChoice) {
862 // Get the field info
863 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
864 // Analyze only after being initialized
865 String fieldClass = fieldInfo.getFullName();
866 // Do the analysis to get Read and Write accesses to fields
867 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
868 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
869 // Record the field in the map
870 if (executedInsn instanceof WriteInstruction) {
871 // We first check the non-relevant fields set
872 if (!nonRelevantFields.contains(fieldInfo)) {
873 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
874 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
875 if (fieldClass.startsWith(str)) {
876 nonRelevantFields.add(fieldInfo);
881 // If we have this field in the non-relevant fields set then we return right away
884 rwSet.addWriteField(fieldClass, objectId);
885 } else if (executedInsn instanceof ReadInstruction) {
886 rwSet.addReadField(fieldClass, objectId);
890 // Analyze Read accesses that are indirect (performed through iterators)
891 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
892 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
894 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
895 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
896 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
897 // Extract info from the stack frame
898 StackFrame frame = ti.getTopFrame();
899 int[] frameSlots = frame.getSlots();
900 // Get the Groovy callsite library at index 0
901 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
902 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
905 // Get the iterated object whose property is accessed
906 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
907 if (eiAccessObj == null) {
910 // We exclude library classes (they start with java, org, etc.) and some more
911 ClassInfo classInfo = eiAccessObj.getClassInfo();
912 String objClassName = classInfo.getName();
913 // Check if this class info is part of the non-relevant classes set already
914 if (!nonRelevantClasses.contains(classInfo)) {
915 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName) ||
916 excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName)) {
917 nonRelevantClasses.add(classInfo);
921 // If it is part of the non-relevant classes set then return immediately
924 // Extract fields from this object and put them into the read write
925 int numOfFields = eiAccessObj.getNumberOfFields();
926 for(int i=0; i<numOfFields; i++) {
927 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
928 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
929 String fieldClass = fieldInfo.getFullName();
930 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
931 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
932 // Record the field in the map
933 rwSet.addReadField(fieldClass, objectId);
939 private int checkAndAdjustChoice(int currentChoice, VM vm) {
940 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
941 // for certain method calls in the infrastructure, e.g., eventSince()
942 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
943 // This is the main event CG
944 if (currentCG instanceof IntIntervalGenerator) {
945 // This is the interval CG used in device handlers
946 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
947 // Iterate until we find the IntChoiceFromSet CG
948 while (!(parentCG instanceof IntChoiceFromSet)) {
949 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
951 // Find the choice related to the IntIntervalGenerator CG from the map
952 currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
954 return currentChoice;
957 private void createBacktrackingPoint(Execution execution, int currentChoice,
958 Execution conflictExecution, int conflictChoice) {
959 // Create a new list of choices for backtrack based on the current choice and conflicting event number
960 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
961 // for the original set {0, 1, 2, 3}
963 // execution/currentChoice represent the event/transaction that will be put into the backtracking set of
964 // conflictExecution/conflictChoice
965 Integer[] newChoiceList = new Integer[refChoices.length];
966 ArrayList<TransitionEvent> currentTrace = execution.getExecutionTrace();
967 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
968 int currChoice = currentTrace.get(currentChoice).getChoice();
969 int stateId = conflictTrace.get(conflictChoice).getStateId();
970 // Check if this trace has been done from this state
971 if (isTraceAlreadyConstructed(currChoice, stateId)) {
974 // Put the conflicting event numbers first and reverse the order
975 newChoiceList[0] = currChoice;
976 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
977 for (int i = 0, j = 1; i < refChoices.length; i++) {
978 if (refChoices[i] != newChoiceList[0]) {
979 newChoiceList[j] = refChoices[i];
983 // Predecessor of the new backtrack point is the same as the conflict point's
984 addNewBacktrackPoint(stateId, newChoiceList, conflictTrace.get(conflictChoice));
987 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
988 for (String excludedField : excludedStrings) {
989 if (className.contains(excludedField)) {
996 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
997 for (String excludedField : excludedStrings) {
998 if (className.endsWith(excludedField)) {
1005 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
1006 for (String excludedField : excludedStrings) {
1007 if (className.startsWith(excludedField)) {
1014 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
1015 // Check if we are reaching the end of our execution: no more backtracking points to explore
1016 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
1017 if (!backtrackStateQ.isEmpty()) {
1018 // Set done all the other backtrack points
1019 for (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
1020 backtrackTransition.getTransitionCG().setDone();
1022 // Reset the next backtrack point with the latest state
1023 int hiStateId = backtrackStateQ.peek();
1024 // Restore the state first if necessary
1025 if (vm.getStateId() != hiStateId) {
1026 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
1027 vm.restoreState(restorableState);
1029 // Set the backtrack CG
1030 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
1031 setBacktrackCG(hiStateId, backtrackCG);
1033 // Set done this last CG (we save a few rounds)
1036 // Save all the visited states when starting a new execution of trace
1037 prevVisitedStates.addAll(currVisitedStates);
1038 // This marks a transitional period to the new CG
1039 isEndOfExecution = true;
1042 private boolean isConflictFound(Execution execution, int reachableChoice, Execution conflictExecution, int conflictChoice,
1043 ReadWriteSet currRWSet) {
1044 // conflictExecution/conflictChoice represent a predecessor event/transaction that can potentially have a conflict
1045 ArrayList<TransitionEvent> executionTrace = execution.getExecutionTrace();
1046 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
1047 HashMap<Integer, ReadWriteSet> confRWFieldsMap = conflictExecution.getReadWriteFieldsMap();
1048 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
1049 if (!confRWFieldsMap.containsKey(conflictChoice) ||
1050 executionTrace.get(reachableChoice).getChoice() == conflictTrace.get(conflictChoice).getChoice()) {
1053 // R/W set of choice/event that may have a potential conflict
1054 ReadWriteSet confRWSet = confRWFieldsMap.get(conflictChoice);
1055 // Check for conflicts with Read and Write fields for Write instructions
1056 Set<String> currWriteSet = currRWSet.getWriteSet();
1057 for(String writeField : currWriteSet) {
1058 int currObjId = currRWSet.writeFieldObjectId(writeField);
1059 if ((confRWSet.readFieldExists(writeField) && confRWSet.readFieldObjectId(writeField) == currObjId) ||
1060 (confRWSet.writeFieldExists(writeField) && confRWSet.writeFieldObjectId(writeField) == currObjId)) {
1061 // Remove this from the write set as we are tracking per memory location
1062 currRWSet.removeWriteField(writeField);
1066 // Check for conflicts with Write fields for Read instructions
1067 Set<String> currReadSet = currRWSet.getReadSet();
1068 for(String readField : currReadSet) {
1069 int currObjId = currRWSet.readFieldObjectId(readField);
1070 if (confRWSet.writeFieldExists(readField) && confRWSet.writeFieldObjectId(readField) == currObjId) {
1071 // Remove this from the read set as we are tracking per memory location
1072 currRWSet.removeReadField(readField);
1076 // Return false if no conflict is found
1080 private ReadWriteSet getReadWriteSet(int currentChoice) {
1081 // Do the analysis to get Read and Write accesses to fields
1083 // We already have an entry
1084 HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
1085 if (currReadWriteFieldsMap.containsKey(currentChoice)) {
1086 rwSet = currReadWriteFieldsMap.get(currentChoice);
1087 } else { // We need to create a new entry
1088 rwSet = new ReadWriteSet();
1089 currReadWriteFieldsMap.put(currentChoice, rwSet);
1094 private boolean isFieldExcluded(Instruction executedInsn) {
1095 // Get the field info
1096 FieldInfo fieldInfo = ((JVMFieldInstruction) executedInsn).getFieldInfo();
1097 // Check if the non-relevant fields set already has it
1098 if (nonRelevantFields.contains(fieldInfo)) {
1101 // Check if the relevant fields set already has it
1102 if (relevantFields.contains(fieldInfo)) {
1105 // Analyze only after being initialized
1106 String field = fieldInfo.getFullName();
1107 // Check against "starts-with", "ends-with", and "contains" list
1108 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
1109 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
1110 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
1111 nonRelevantFields.add(fieldInfo);
1114 relevantFields.add(fieldInfo);
1118 // Check if this trace is already constructed
1119 private boolean isTraceAlreadyConstructed(int firstChoice, int stateId) {
1120 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
1121 // Check if the trace has been constructed as a backtrack point for this state
1122 // TODO: THIS IS AN OPTIMIZATION!
1123 HashSet<Integer> choiceSet;
1124 if (doneBacktrackMap.containsKey(stateId)) {
1125 choiceSet = doneBacktrackMap.get(stateId);
1126 if (choiceSet.contains(firstChoice)) {
1130 choiceSet = new HashSet<>();
1131 doneBacktrackMap.put(stateId, choiceSet);
1133 choiceSet.add(firstChoice);
1138 // Reset data structure for each new execution
1139 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
1140 if (choices == null || choices != icsCG.getAllChoices()) {
1141 // Reset state variables
1143 choices = icsCG.getAllChoices();
1144 refChoices = copyChoices(choices);
1145 // Clear data structures
1146 currVisitedStates = new HashSet<>();
1147 stateToEventMap = new HashMap<>();
1148 isEndOfExecution = false;
1152 // Set a backtrack point for a particular state
1153 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
1154 // Set a backtrack CG based on a state ID
1155 LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
1156 BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
1157 backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
1158 backtrackCG.setStateId(stateId);
1159 backtrackCG.reset();
1160 // Update current execution with this new execution
1161 Execution newExecution = new Execution();
1162 TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
1163 newExecution.addTransition(firstTransition);
1164 // Try to free some memory since this map is only used for the current execution
1165 currentExecution.clearCGToChoiceMap();
1166 currentExecution = newExecution;
1167 // Remove from the queue if we don't have more backtrack points for that state
1168 if (backtrackExecutions.isEmpty()) {
1169 backtrackMap.remove(stateId);
1170 backtrackStateQ.remove(stateId);
1174 // Update backtrack sets
1175 // 1) recursively, and
1176 // 2) track accesses per memory location (per shared variable/field)
1177 private void updateBacktrackSet(Execution execution, int currentChoice) {
1178 // Copy ReadWriteSet object
1179 HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
1180 ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice);
1181 if (currRWSet == null) {
1184 currRWSet = currRWSet.getCopy();
1185 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1186 HashSet<TransitionEvent> visited = new HashSet<>();
1187 // Update backtrack set recursively
1188 updateBacktrackSetRecursive(execution, currentChoice, execution, currentChoice, currRWSet, visited, false);
1191 // Recursive method to perform backward DFS to traverse the graph
1192 private void updateBacktrackSetRecursive(Execution execution, int currentChoice,
1193 Execution conflictExecution, int conflictChoice,
1194 ReadWriteSet currRWSet, HashSet<TransitionEvent> visited,
1196 TransitionEvent currTrans = execution.getExecutionTrace().get(currentChoice);
1197 if (visited.contains(currTrans)) {
1200 visited.add(currTrans);
1201 TransitionEvent confTrans = conflictExecution.getExecutionTrace().get(conflictChoice);
1202 // Record this transition into rGraph summary
1203 currRWSet = currTrans.recordTransitionSummary(confTrans, currRWSet, refresh);
1204 // Halt when we have found the first read/write conflicts for all memory locations
1205 if (currRWSet.isEmpty()) {
1208 // Explore all predecessors
1209 for (Predecessor predecessor : currTrans.getPredecessors()) {
1210 // Get the predecessor (previous conflict choice)
1211 int predecessorChoice = predecessor.getChoice();
1212 Execution predecessorExecution = predecessor.getExecution();
1213 // Push up one happens-before transition
1214 int newConflictChoice = conflictChoice;
1215 Execution newConflictExecution = conflictExecution;
1216 // Check if a conflict is found
1217 if (isConflictFound(conflictExecution, conflictChoice, predecessorExecution, predecessorChoice, currRWSet)) {
1218 createBacktrackingPoint(conflictExecution, conflictChoice, predecessorExecution, predecessorChoice);
1219 newConflictChoice = predecessorChoice;
1220 newConflictExecution = predecessorExecution;
1222 // Continue performing DFS if conflict is not found
1223 updateBacktrackSetRecursive(predecessorExecution, predecessorChoice, newConflictExecution, newConflictChoice,
1224 currRWSet, visited, refresh);
1228 // --- Functions related to the reachability analysis when there is a state match
1230 private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
1231 // Perform this analysis only when:
1232 // 1) this is not during a switch to a new execution,
1233 // 2) at least 2 choices/events have been explored (choiceCounter > 1),
1234 // 3) state > 0 (state 0 is for boolean CG)
1235 if (!isEndOfExecution && choiceCounter > 1 && stateId > 0) {
1236 if (currVisitedStates.contains(stateId) || prevVisitedStates.contains(stateId)) {
1237 // Update reachable transitions in the graph with a predecessor
1238 HashSet<TransitionEvent> reachableTransitions = rGraph.getReachableTransitionsAtState(stateId);
1239 for(TransitionEvent transition : reachableTransitions) {
1240 transition.recordPredecessor(currentExecution, choiceCounter - 1);
1242 updateBacktrackSetsFromPreviousExecution(stateId);
1247 private void updateBacktrackSetsFromPreviousExecution(int stateId) {
1248 // Collect all the reachable transitions from R-Graph
1249 HashSet<TransitionEvent> reachableTransitions = rGraph.getReachableTransitionsAtState(stateId);
1250 for(TransitionEvent transition : reachableTransitions) {
1251 // Current transition that stems from this state ID
1252 Execution currentExecution = transition.getExecution();
1253 int currentChoice = transition.getChoiceCounter();
1254 // Iterate over the stored conflict transitions in the summary
1255 for(Map.Entry<Integer, SummaryNode> conflictTransition : transition.getTransitionSummary().entrySet()) {
1256 SummaryNode summaryNode = conflictTransition.getValue();
1257 // Conflict transition in the summary node
1258 TransitionEvent confTrans = summaryNode.getTransitionEvent();
1259 Execution conflictExecution = confTrans.getExecution();
1260 int conflictChoice = confTrans.getChoiceCounter();
1261 // Copy ReadWriteSet object
1262 ReadWriteSet currRWSet = summaryNode.getReadWriteSet();
1263 currRWSet = currRWSet.getCopy();
1264 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1265 HashSet<TransitionEvent> visited = new HashSet<>();
1266 updateBacktrackSetRecursive(currentExecution, currentChoice, conflictExecution,
1267 conflictChoice, currRWSet, visited, true);