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;
38 * This a DPOR implementation for event-driven applications with loops that create cycles of state matching
39 * In this new DPOR algorithm/implementation, each run is terminated iff:
40 * - we find a state that matches a state in a previous run, or
41 * - we have a matched state in the current run that consists of cycles that contain all choices/events.
43 public class DPORStateReducer extends ListenerAdapter {
45 // Information printout fields for verbose mode
46 private boolean verboseMode;
47 private boolean stateReductionMode;
48 private final PrintWriter out;
49 private PrintWriter fileWriter;
50 private String detail;
53 private Transition transition;
55 // DPOR-related fields
57 private Integer[] choices;
58 private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
59 private int choiceCounter;
60 private int maxEventChoice;
61 // Data structure to track the events seen by each state to track cycles (containing all events) for termination
62 private HashSet<Integer> currVisitedStates; // States being visited in the current execution
63 private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
64 private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
65 private HashMap<Integer, HashSet<Integer>> stateToEventMap;
66 // Data structure to analyze field Read/Write accesses and conflicts
67 private HashMap<Integer, LinkedList<BacktrackExecution>> backtrackMap; // Track created backtracking points
68 private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
69 private Execution currentExecution; // Holds the information about the current execution
70 private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
71 private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
72 private RGraph rGraph; // R-Graph for past executions
75 private boolean isBooleanCGFlipped;
76 private boolean isEndOfExecution;
79 private int numOfConflicts;
80 private int numOfTransitions;
82 public DPORStateReducer(Config config, JPF jpf) {
83 verboseMode = config.getBoolean("printout_state_transition", false);
84 stateReductionMode = config.getBoolean("activate_state_reduction", true);
86 out = new PrintWriter(System.out, true);
90 String outputFile = config.getString("file_output");
91 if (!outputFile.isEmpty()) {
93 fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
94 } catch (IOException e) {
97 isBooleanCGFlipped = false;
100 restorableStateMap = new HashMap<>();
101 initializeStatesVariables();
105 public void stateRestored(Search search) {
107 id = search.getStateId();
108 depth = search.getDepth();
109 transition = search.getTransition();
111 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
112 " and depth: " + depth + "\n");
117 public void searchStarted(Search search) {
119 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
124 public void stateAdvanced(Search search) {
126 id = search.getStateId();
127 depth = search.getDepth();
128 transition = search.getTransition();
129 if (search.isNewState()) {
135 if (search.isEndState()) {
136 out.println("\n==> DEBUG: This is the last state!\n");
139 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
140 " which is " + detail + " Transition: " + transition + "\n");
142 if (stateReductionMode) {
143 updateStateInfo(search);
148 public void stateBacktracked(Search search) {
150 id = search.getStateId();
151 depth = search.getDepth();
152 transition = search.getTransition();
155 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
156 " and depth: " + depth + "\n");
158 if (stateReductionMode) {
159 updateStateInfo(search);
163 static Logger log = JPF.getLogger("report");
166 public void searchFinished(Search search) {
167 if (stateReductionMode) {
168 // Number of conflicts = first trace + subsequent backtrack points
169 numOfConflicts += 1 + doneBacktrackSet.size();
172 out.println("\n==> DEBUG: ----------------------------------- search finished");
173 out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
174 out.println("\n==> DEBUG: Number of conflicts : " + numOfConflicts);
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 conflicts : " + numOfConflicts);
180 fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
181 fileWriter.println();
187 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
188 if (stateReductionMode) {
189 // Initialize with necessary information from the CG
190 if (nextCG instanceof IntChoiceFromSet) {
191 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
192 if (!isEndOfExecution) {
193 // Check if CG has been initialized, otherwise initialize it
194 Integer[] cgChoices = icsCG.getAllChoices();
195 // Record the events (from choices)
196 if (choices == null) {
198 // Make a copy of choices as reference
199 refChoices = copyChoices(choices);
200 // Record the max event choice (the last element of the choice array)
201 maxEventChoice = choices[choices.length - 1];
203 icsCG.setNewValues(choices);
205 // Use a modulo since choiceCounter is going to keep increasing
206 int choiceIndex = choiceCounter % choices.length;
207 icsCG.advance(choices[choiceIndex]);
209 // Set done all CGs while transitioning to a new execution
217 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
218 if (stateReductionMode) {
219 // Check the boolean CG and if it is flipped, we are resetting the analysis
220 if (currentCG instanceof BooleanChoiceGenerator) {
221 if (!isBooleanCGFlipped) {
222 isBooleanCGFlipped = true;
224 // Number of conflicts = first trace + subsequent backtrack points
225 numOfConflicts = 1 + doneBacktrackSet.size();
226 // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
227 initializeStatesVariables();
230 // Check every choice generated and ensure fair scheduling!
231 if (currentCG instanceof IntChoiceFromSet) {
232 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
233 // If this is a new CG then we need to update data structures
234 resetStatesForNewExecution(icsCG, vm);
235 // If we don't see a fair scheduling of events/choices then we have to enforce it
236 ensureFairSchedulingAndSetupTransition(icsCG, vm);
237 // Update backtrack set of an executed event (transition): one transition before this one
238 updateBacktrackSet(currentExecution, choiceCounter - 1);
239 // Explore the next backtrack point:
240 // 1) if we have seen this state or this state contains cycles that involve all events, and
241 // 2) after the current CG is advanced at least once
242 if (terminateCurrentExecution() && choiceCounter > 0) {
243 exploreNextBacktrackPoints(vm, icsCG);
247 // Map state to event
248 mapStateToEvent(icsCG.getNextChoice());
249 justVisitedStates.clear();
258 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
259 if (stateReductionMode) {
260 if (!isEndOfExecution) {
261 // Has to be initialized and a integer CG
262 ChoiceGenerator<?> cg = vm.getChoiceGenerator();
263 if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
264 int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
265 if (currentChoice < 0) { // If choice is -1 then skip
268 currentChoice = checkAndAdjustChoice(currentChoice, vm);
269 // Record accesses from executed instructions
270 if (executedInsn instanceof JVMFieldInstruction) {
271 // Analyze only after being initialized
272 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
273 // We don't care about libraries
274 if (!isFieldExcluded(fieldClass)) {
275 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
277 } else if (executedInsn instanceof INVOKEINTERFACE) {
278 // Handle the read/write accesses that occur through iterators
279 analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
291 // This class compactly stores backtrack execution:
292 // 1) backtrack choice list, and
293 // 2) first backtrack point (linking with predecessor execution)
294 private class BacktrackExecution {
295 private Integer[] choiceList;
296 private TransitionEvent firstTransition;
298 public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
299 choiceList = choList;
300 firstTransition = fTransition;
303 public Integer[] getChoiceList() {
307 public TransitionEvent getFirstTransition() {
308 return firstTransition;
312 // This class stores a representation of an execution
313 // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
314 // TODO: We basically need to keep track of:
315 // TODO: (1) last read/write access to each memory location
316 // TODO: (2) last state with two or more incoming events/transitions
317 private class Execution {
318 private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
319 private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
320 private boolean isNew; // Track if this is the first time it is accessed
321 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
322 private HashMap<Integer, TransitionEvent> stateToTransitionMap; // For O(1) access to backtrack point
325 cgToChoiceMap = new HashMap<>();
326 executionTrace = new ArrayList<>();
328 readWriteFieldsMap = new HashMap<>();
329 stateToTransitionMap = new HashMap<>();
332 public void addTransition(TransitionEvent newBacktrackPoint) {
333 executionTrace.add(newBacktrackPoint);
336 public void clearCGToChoiceMap() {
337 cgToChoiceMap = null;
340 public int getChoiceFromCG(IntChoiceFromSet icsCG) {
341 return cgToChoiceMap.get(icsCG);
344 public ArrayList<TransitionEvent> getExecutionTrace() {
345 return executionTrace;
348 public TransitionEvent getFirstTransition() {
349 return executionTrace.get(0);
352 public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
353 return readWriteFieldsMap;
356 public TransitionEvent getTransitionFromState(int stateId) {
357 if (stateToTransitionMap.containsKey(stateId)) {
358 return stateToTransitionMap.get(stateId);
360 // Return the latest transition for unseen states (that have just been encountered in this transition)
361 return executionTrace.get(executionTrace.size() - 1);
364 public boolean isNew() {
366 // Right after this is accessed, it is no longer new
373 public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
374 cgToChoiceMap.put(icsCG, choice);
377 public void mapStateToTransition(int stateId, TransitionEvent backtrackPoint) {
378 stateToTransitionMap.put(stateId, backtrackPoint);
382 // This class compactly stores a predecessor
383 // 1) a predecessor execution
384 // 2) the predecessor choice in that predecessor execution
385 private class Predecessor {
386 private int choice; // Predecessor choice
387 private Execution execution; // Predecessor execution
389 public Predecessor(int predChoice, Execution predExec) {
391 execution = predExec;
394 public int getChoice() {
398 public Execution getExecution() {
403 // This class represents a R-Graph (in the paper it is a state transition graph R)
404 // This implementation stores reachable transitions from and connects with past executions
405 private class RGraph {
406 private int hiStateId; // Maximum state Id
407 private HashMap<Integer, HashSet<TransitionEvent>> graph; // Reachable transitions from past executions
411 graph = new HashMap<>();
414 public void addReachableTransition(int stateId, TransitionEvent transition) {
415 HashSet<TransitionEvent> transitionSet;
416 if (graph.containsKey(stateId)) {
417 transitionSet = graph.get(stateId);
419 transitionSet = new HashSet<>();
420 graph.put(stateId, transitionSet);
422 // Insert into the set if it does not contain it yet
423 if (!transitionSet.contains(transition)) {
424 transitionSet.add(transition);
426 // Update highest state ID
427 if (hiStateId < stateId) {
432 public HashSet<TransitionEvent> getReachableTransitionsAtState(int stateId) {
433 return graph.get(stateId);
436 public HashSet<TransitionEvent> getReachableTransitions(int stateId) {
437 HashSet<TransitionEvent> reachableTransitions = new HashSet<>();
438 // All transitions from states higher than the given state ID (until the highest state ID) are reachable
439 for(int stId = stateId; stId <= hiStateId; stId++) {
440 reachableTransitions.addAll(graph.get(stId));
442 return reachableTransitions;
446 // This class compactly stores Read and Write field sets
447 // We store the field name and its object ID
448 // Sharing the same field means the same field name and object ID
449 private class ReadWriteSet {
450 private HashMap<String, Integer> readMap;
451 private HashMap<String, Integer> writeMap;
453 public ReadWriteSet() {
454 readMap = new HashMap<>();
455 writeMap = new HashMap<>();
458 public void addReadField(String field, int objectId) {
459 readMap.put(field, objectId);
462 public void addWriteField(String field, int objectId) {
463 writeMap.put(field, objectId);
466 public void removeReadField(String field) {
467 readMap.remove(field);
470 public void removeWriteField(String field) {
471 writeMap.remove(field);
474 public boolean isEmpty() {
475 return readMap.isEmpty() && writeMap.isEmpty();
478 public ReadWriteSet getCopy() {
479 ReadWriteSet copyRWSet = new ReadWriteSet();
480 // Copy the maps in the set into the new object copy
481 copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
482 copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
486 public Set<String> getReadSet() {
487 return readMap.keySet();
490 public Set<String> getWriteSet() {
491 return writeMap.keySet();
494 public boolean readFieldExists(String field) {
495 return readMap.containsKey(field);
498 public boolean writeFieldExists(String field) {
499 return writeMap.containsKey(field);
502 public int readFieldObjectId(String field) {
503 return readMap.get(field);
506 public int writeFieldObjectId(String field) {
507 return writeMap.get(field);
510 private HashMap<String, Integer> getReadMap() {
514 private HashMap<String, Integer> getWriteMap() {
518 private void setReadMap(HashMap<String, Integer> rMap) {
522 private void setWriteMap(HashMap<String, Integer> wMap) {
527 // This class compactly stores transitions:
531 // 4) predecessors (for backward DFS).
532 private class TransitionEvent {
533 private int choice; // Choice chosen at this transition
534 private int choiceCounter; // Choice counter at this transition
535 private Execution execution; // The execution where this transition belongs
536 private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
537 private int stateId; // State at this transition
538 private IntChoiceFromSet transitionCG; // CG at this transition
540 public TransitionEvent() {
544 predecessors = new HashSet<>();
549 public int getChoice() {
553 public int getChoiceCounter() {
554 return choiceCounter;
557 public Execution getExecution() {
561 public HashSet<Predecessor> getPredecessors() {
565 public int getStateId() {
569 public IntChoiceFromSet getTransitionCG() { return transitionCG; }
571 public void recordPredecessor(Execution execution, int choice) {
572 predecessors.add(new Predecessor(choice, execution));
575 public void setChoice(int cho) {
579 public void setChoiceCounter(int choCounter) {
580 choiceCounter = choCounter;
583 public void setExecution(Execution exec) {
587 public void setPredecessors(HashSet<Predecessor> preds) {
588 predecessors = new HashSet<>(preds);
591 public void setStateId(int stId) {
595 public void setTransitionCG(IntChoiceFromSet cg) {
601 private final static String DO_CALL_METHOD = "doCall";
602 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
603 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
604 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
605 // Groovy library created fields
606 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
608 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
609 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
610 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
611 // Java and Groovy libraries
612 { "java", "org", "sun", "com", "gov", "groovy"};
613 private final static String[] EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
614 private final static String GET_PROPERTY_METHOD =
615 "invokeinterface org.codehaus.groovy.runtime.callsite.CallSite.callGetProperty";
616 private final static String GROOVY_CALLSITE_LIB = "org.codehaus.groovy.runtime.callsite";
617 private final static String JAVA_INTEGER = "int";
618 private final static String JAVA_STRING_LIB = "java.lang.String";
621 private Integer[] copyChoices(Integer[] choicesToCopy) {
623 Integer[] copyOfChoices = new Integer[choicesToCopy.length];
624 System.arraycopy(choicesToCopy, 0, copyOfChoices, 0, choicesToCopy.length);
625 return copyOfChoices;
628 private void ensureFairSchedulingAndSetupTransition(IntChoiceFromSet icsCG, VM vm) {
629 // Check the next choice and if the value is not the same as the expected then force the expected value
630 int choiceIndex = choiceCounter % refChoices.length;
631 int nextChoice = icsCG.getNextChoice();
632 if (refChoices[choiceIndex] != nextChoice) {
633 int expectedChoice = refChoices[choiceIndex];
634 int currCGIndex = icsCG.getNextChoiceIndex();
635 if ((currCGIndex >= 0) && (currCGIndex < refChoices.length)) {
636 icsCG.setChoice(currCGIndex, expectedChoice);
639 // Get state ID and associate it with this transition
640 int stateId = vm.getStateId();
641 TransitionEvent transition = setupTransition(icsCG, stateId, choiceIndex);
642 // Add new transition to the current execution and map it in R-Graph
643 for (Integer stId : justVisitedStates) { // Map this transition to all the previously passed states
644 rGraph.addReachableTransition(stId, transition);
645 currentExecution.mapStateToTransition(stId, transition);
647 currentExecution.mapCGToChoice(icsCG, choiceCounter);
648 // Store restorable state object for this state (always store the latest)
649 RestorableVMState restorableState = vm.getRestorableState();
650 restorableStateMap.put(stateId, restorableState);
653 private TransitionEvent setupTransition(IntChoiceFromSet icsCG, int stateId, int choiceIndex) {
654 // Get a new transition
655 TransitionEvent transition;
656 if (currentExecution.isNew()) {
657 // We need to handle the first transition differently because this has a predecessor execution
658 transition = currentExecution.getFirstTransition();
660 transition = new TransitionEvent();
661 currentExecution.addTransition(transition);
662 transition.recordPredecessor(currentExecution, choiceCounter - 1);
664 transition.setExecution(currentExecution);
665 transition.setTransitionCG(icsCG);
666 transition.setStateId(stateId);
667 transition.setChoice(refChoices[choiceIndex]);
668 transition.setChoiceCounter(choiceCounter);
673 // --- Functions related to cycle detection and reachability graph
675 // Detect cycles in the current execution/trace
676 // We terminate the execution iff:
677 // (1) the state has been visited in the current execution
678 // (2) the state has one or more cycles that involve all the events
679 // With simple approach we only need to check for a re-visited state.
680 // Basically, we have to check that we have executed all events between two occurrences of such state.
681 private boolean completeFullCycle(int stId) {
682 // False if the state ID hasn't been recorded
683 if (!stateToEventMap.containsKey(stId)) {
686 HashSet<Integer> visitedEvents = stateToEventMap.get(stId);
687 // Check if this set contains all the event choices
688 // If not then this is not the terminating condition
689 for(int i=0; i<=maxEventChoice; i++) {
690 if (!visitedEvents.contains(i)) {
697 private void initializeStatesVariables() {
704 currVisitedStates = new HashSet<>();
705 justVisitedStates = new HashSet<>();
706 prevVisitedStates = new HashSet<>();
707 stateToEventMap = new HashMap<>();
709 backtrackMap = new HashMap<>();
710 backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
711 currentExecution = new Execution();
712 currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
713 doneBacktrackSet = new HashSet<>();
714 rGraph = new RGraph();
716 isEndOfExecution = false;
719 private void mapStateToEvent(int nextChoiceValue) {
720 // Update all states with this event/choice
721 // This means that all past states now see this transition
722 Set<Integer> stateSet = stateToEventMap.keySet();
723 for(Integer stateId : stateSet) {
724 HashSet<Integer> eventSet = stateToEventMap.get(stateId);
725 eventSet.add(nextChoiceValue);
729 private boolean terminateCurrentExecution() {
730 // We need to check all the states that have just been visited
731 // Often a transition (choice/event) can result into forwarding/backtracking to a number of states
732 for(Integer stateId : justVisitedStates) {
733 if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
740 private void updateStateInfo(Search search) {
741 // Update the state variables
742 int stateId = search.getStateId();
743 // Insert state ID into the map if it is new
744 if (!stateToEventMap.containsKey(stateId)) {
745 HashSet<Integer> eventSet = new HashSet<>();
746 stateToEventMap.put(stateId, eventSet);
748 analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
749 justVisitedStates.add(stateId);
750 if (!prevVisitedStates.contains(stateId)) {
751 // It is a currently visited states if the state has not been seen in previous executions
752 currVisitedStates.add(stateId);
756 // --- Functions related to Read/Write access analysis on shared fields
758 private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList, TransitionEvent conflictTransition) {
759 // Insert backtrack point to the right state ID
760 LinkedList<BacktrackExecution> backtrackExecList;
761 if (backtrackMap.containsKey(stateId)) {
762 backtrackExecList = backtrackMap.get(stateId);
764 backtrackExecList = new LinkedList<>();
765 backtrackMap.put(stateId, backtrackExecList);
767 // Add the new backtrack execution object
768 TransitionEvent backtrackTransition = new TransitionEvent();
769 backtrackTransition.setPredecessors(conflictTransition.getPredecessors());
770 backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
771 // Add to priority queue
772 if (!backtrackStateQ.contains(stateId)) {
773 backtrackStateQ.add(stateId);
777 // Analyze Read/Write accesses that are directly invoked on fields
778 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
779 // Do the analysis to get Read and Write accesses to fields
780 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
781 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
782 // Record the field in the map
783 if (executedInsn instanceof WriteInstruction) {
784 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
785 for (String str : EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
786 if (fieldClass.startsWith(str)) {
790 rwSet.addWriteField(fieldClass, objectId);
791 } else if (executedInsn instanceof ReadInstruction) {
792 rwSet.addReadField(fieldClass, objectId);
796 // Analyze Read accesses that are indirect (performed through iterators)
797 // These accesses are marked by certain bytecode instructions, e.g., INVOKEINTERFACE
798 private void analyzeReadWriteAccesses(Instruction instruction, ThreadInfo ti, int currentChoice) {
800 INVOKEINTERFACE insn = (INVOKEINTERFACE) instruction;
801 if (insn.toString().startsWith(GET_PROPERTY_METHOD) &&
802 insn.getMethodInfo().getName().equals(DO_CALL_METHOD)) {
803 // Extract info from the stack frame
804 StackFrame frame = ti.getTopFrame();
805 int[] frameSlots = frame.getSlots();
806 // Get the Groovy callsite library at index 0
807 ElementInfo eiCallsite = VM.getVM().getHeap().get(frameSlots[0]);
808 if (!eiCallsite.getClassInfo().getName().startsWith(GROOVY_CALLSITE_LIB)) {
811 // Get the iterated object whose property is accessed
812 ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
813 if (eiAccessObj == null) {
816 // We exclude library classes (they start with java, org, etc.) and some more
817 String objClassName = eiAccessObj.getClassInfo().getName();
818 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
819 excludeThisForItStartsWith(EXCLUDED_FIELDS_READ_WRITE_INSTRUCTIONS_STARTS_WITH_LIST, objClassName)) {
822 // Extract fields from this object and put them into the read write
823 int numOfFields = eiAccessObj.getNumberOfFields();
824 for(int i=0; i<numOfFields; i++) {
825 FieldInfo fieldInfo = eiAccessObj.getFieldInfo(i);
826 if (fieldInfo.getType().equals(JAVA_STRING_LIB) || fieldInfo.getType().equals(JAVA_INTEGER)) {
827 String fieldClass = fieldInfo.getFullName();
828 ReadWriteSet rwSet = getReadWriteSet(currentChoice);
829 int objectId = fieldInfo.getClassInfo().getClassObjectRef();
830 // Record the field in the map
831 rwSet.addReadField(fieldClass, objectId);
837 private int checkAndAdjustChoice(int currentChoice, VM vm) {
838 // If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
839 // for certain method calls in the infrastructure, e.g., eventSince()
840 ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
841 // This is the main event CG
842 if (currentCG instanceof IntIntervalGenerator) {
843 // This is the interval CG used in device handlers
844 ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
845 // Iterate until we find the IntChoiceFromSet CG
846 while (!(parentCG instanceof IntChoiceFromSet)) {
847 parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
849 // Find the choice related to the IntIntervalGenerator CG from the map
850 currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
852 return currentChoice;
855 private void createBacktrackingPoint(Execution execution, int currentChoice,
856 Execution conflictExecution, int conflictChoice) {
857 // Create a new list of choices for backtrack based on the current choice and conflicting event number
858 // E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
859 // for the original set {0, 1, 2, 3}
860 Integer[] newChoiceList = new Integer[refChoices.length];
861 ArrayList<TransitionEvent> currentTrace = execution.getExecutionTrace();
862 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
863 int currChoice = currentTrace.get(currentChoice).getChoice();
864 int stateId = conflictTrace.get(conflictChoice).getStateId();
865 // Check if this trace has been done from this state
866 if (isTraceAlreadyConstructed(currChoice, stateId)) {
869 // Put the conflicting event numbers first and reverse the order
870 newChoiceList[0] = currChoice;
871 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
872 for (int i = 0, j = 1; i < refChoices.length; i++) {
873 if (refChoices[i] != newChoiceList[0]) {
874 newChoiceList[j] = refChoices[i];
878 // Predecessor of the new backtrack point is the same as the conflict point's
879 addNewBacktrackPoint(stateId, newChoiceList, conflictTrace.get(conflictChoice));
882 private boolean excludeThisForItContains(String[] excludedStrings, String className) {
883 for (String excludedField : excludedStrings) {
884 if (className.contains(excludedField)) {
891 private boolean excludeThisForItEndsWith(String[] excludedStrings, String className) {
892 for (String excludedField : excludedStrings) {
893 if (className.endsWith(excludedField)) {
900 private boolean excludeThisForItStartsWith(String[] excludedStrings, String className) {
901 for (String excludedField : excludedStrings) {
902 if (className.startsWith(excludedField)) {
909 private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
910 // Check if we are reaching the end of our execution: no more backtracking points to explore
911 // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
912 if (!backtrackStateQ.isEmpty()) {
913 // Set done all the other backtrack points
914 for (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
915 backtrackTransition.getTransitionCG().setDone();
917 // Reset the next backtrack point with the latest state
918 int hiStateId = backtrackStateQ.peek();
919 // Restore the state first if necessary
920 if (vm.getStateId() != hiStateId) {
921 RestorableVMState restorableState = restorableStateMap.get(hiStateId);
922 vm.restoreState(restorableState);
924 // Set the backtrack CG
925 IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
926 setBacktrackCG(hiStateId, backtrackCG);
928 // Set done this last CG (we save a few rounds)
931 // Save all the visited states when starting a new execution of trace
932 prevVisitedStates.addAll(currVisitedStates);
933 // This marks a transitional period to the new CG
934 isEndOfExecution = true;
937 private boolean isConflictFound(Execution execution, int reachableChoice, Execution conflictExecution, int conflictChoice,
938 ReadWriteSet currRWSet) {
939 ArrayList<TransitionEvent> executionTrace = execution.getExecutionTrace();
940 HashMap<Integer, ReadWriteSet> execRWFieldsMap = execution.getReadWriteFieldsMap();
941 ArrayList<TransitionEvent> conflictTrace = conflictExecution.getExecutionTrace();
942 // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
943 if (!execRWFieldsMap.containsKey(conflictChoice) ||
944 executionTrace.get(reachableChoice).getChoice() == conflictTrace.get(conflictChoice).getChoice()) {
947 // R/W set of choice/event that may have a potential conflict
948 ReadWriteSet evtRWSet = execRWFieldsMap.get(conflictChoice);
949 // Check for conflicts with Read and Write fields for Write instructions
950 Set<String> currWriteSet = currRWSet.getWriteSet();
951 for(String writeField : currWriteSet) {
952 int currObjId = currRWSet.writeFieldObjectId(writeField);
953 if ((evtRWSet.readFieldExists(writeField) && evtRWSet.readFieldObjectId(writeField) == currObjId) ||
954 (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId)) {
955 // Remove this from the write set as we are tracking per memory location
956 currRWSet.removeWriteField(writeField);
960 // Check for conflicts with Write fields for Read instructions
961 Set<String> currReadSet = currRWSet.getReadSet();
962 for(String readField : currReadSet) {
963 int currObjId = currRWSet.readFieldObjectId(readField);
964 if (evtRWSet.writeFieldExists(readField) && evtRWSet.writeFieldObjectId(readField) == currObjId) {
965 // Remove this from the read set as we are tracking per memory location
966 currRWSet.removeReadField(readField);
970 // Return false if no conflict is found
974 private ReadWriteSet getReadWriteSet(int currentChoice) {
975 // Do the analysis to get Read and Write accesses to fields
977 // We already have an entry
978 HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
979 if (currReadWriteFieldsMap.containsKey(currentChoice)) {
980 rwSet = currReadWriteFieldsMap.get(currentChoice);
981 } else { // We need to create a new entry
982 rwSet = new ReadWriteSet();
983 currReadWriteFieldsMap.put(currentChoice, rwSet);
988 private boolean isFieldExcluded(String field) {
989 // Check against "starts-with", "ends-with", and "contains" list
990 if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
991 excludeThisForItEndsWith(EXCLUDED_FIELDS_ENDS_WITH_LIST, field) ||
992 excludeThisForItContains(EXCLUDED_FIELDS_CONTAINS_LIST, field)) {
999 // Check if this trace is already constructed
1000 private boolean isTraceAlreadyConstructed(int firstChoice, int stateId) {
1001 // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
1002 // TODO: THIS IS AN OPTIMIZATION!
1003 // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
1004 // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
1005 // The second time this event 1 is explored, it will generate the same state as the first one
1006 StringBuilder sb = new StringBuilder();
1009 sb.append(firstChoice);
1010 // Check if the trace has been constructed as a backtrack point for this state
1011 if (doneBacktrackSet.contains(sb.toString())) {
1014 doneBacktrackSet.add(sb.toString());
1018 // Reset data structure for each new execution
1019 private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
1020 if (choices == null || choices != icsCG.getAllChoices()) {
1021 // Reset state variables
1023 choices = icsCG.getAllChoices();
1024 refChoices = copyChoices(choices);
1025 // Clear data structures
1026 currVisitedStates = new HashSet<>();
1027 stateToEventMap = new HashMap<>();
1028 isEndOfExecution = false;
1032 // Set a backtrack point for a particular state
1033 private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
1034 // Set a backtrack CG based on a state ID
1035 LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
1036 BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
1037 backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
1038 backtrackCG.setStateId(stateId);
1039 backtrackCG.reset();
1040 // Update current execution with this new execution
1041 Execution newExecution = new Execution();
1042 TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
1043 newExecution.addTransition(firstTransition);
1044 // Try to free some memory since this map is only used for the current execution
1045 currentExecution.clearCGToChoiceMap();
1046 currentExecution = newExecution;
1047 // Remove from the queue if we don't have more backtrack points for that state
1048 if (backtrackExecutions.isEmpty()) {
1049 backtrackMap.remove(stateId);
1050 backtrackStateQ.remove(stateId);
1054 // Update backtrack sets
1055 // 1) recursively, and
1056 // 2) track accesses per memory location (per shared variable/field)
1057 private void updateBacktrackSet(Execution execution, int currentChoice) {
1058 // Copy ReadWriteSet object
1059 HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
1060 ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice);
1061 if (currRWSet == null) {
1064 currRWSet = currRWSet.getCopy();
1065 // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
1066 HashSet<TransitionEvent> visited = new HashSet<>();
1067 // Update backtrack set recursively
1068 // TODO: The following is the call to the original version of the method
1069 // updateBacktrackSetRecursive(execution, currentChoice, execution, currentChoice, currRWSet, visited);
1070 // TODO: The following is the call to the version of the method with pushing up happens-before transitions
1071 updateBacktrackSetRecursive(execution, currentChoice, execution, currentChoice, execution, currentChoice, currRWSet, visited);
1074 // TODO: This is the original version of the recursive method
1075 // private void updateBacktrackSetRecursive(Execution execution, int currentChoice,
1076 // Execution conflictExecution, int conflictChoice,
1077 // ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
1078 // // Halt when we have found the first read/write conflicts for all memory locations
1079 // if (currRWSet.isEmpty()) {
1082 // TransitionEvent confTrans = conflictExecution.getExecutionTrace().get(conflictChoice);
1083 // // Halt when we have visited this transition (in a cycle)
1084 // if (visited.contains(confTrans)) {
1087 // visited.add(confTrans);
1088 // // Explore all predecessors
1089 // for (Predecessor predecessor : confTrans.getPredecessors()) {
1090 // // Get the predecessor (previous conflict choice)
1091 // conflictChoice = predecessor.getChoice();
1092 // conflictExecution = predecessor.getExecution();
1093 // // Check if a conflict is found
1094 // if (isConflictFound(execution, currentChoice, conflictExecution, conflictChoice, currRWSet)) {
1095 // createBacktrackingPoint(execution, currentChoice, conflictExecution, conflictChoice);
1097 // // Continue performing DFS if conflict is not found
1098 // updateBacktrackSetRecursive(execution, currentChoice, conflictExecution, conflictChoice, currRWSet, visited);
1102 // TODO: This is the version of the method with pushing up happens-before transitions
1103 private void updateBacktrackSetRecursive(Execution execution, int currentChoice,
1104 Execution conflictExecution, int conflictChoice,
1105 Execution hbExecution, int hbChoice,
1106 ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
1107 // Halt when we have found the first read/write conflicts for all memory locations
1108 if (currRWSet.isEmpty()) {
1111 TransitionEvent confTrans = conflictExecution.getExecutionTrace().get(conflictChoice);
1112 // Halt when we have visited this transition (in a cycle)
1113 if (visited.contains(confTrans)) {
1116 visited.add(confTrans);
1117 // Explore all predecessors
1118 for (Predecessor predecessor : confTrans.getPredecessors()) {
1119 // Get the predecessor (previous conflict choice)
1120 conflictChoice = predecessor.getChoice();
1121 conflictExecution = predecessor.getExecution();
1122 // Push up one happens-before transition
1123 int pushedChoice = hbChoice;
1124 Execution pushedExecution = hbExecution;
1125 // Check if a conflict is found
1126 if (isConflictFound(execution, currentChoice, conflictExecution, conflictChoice, currRWSet)) {
1127 createBacktrackingPoint(pushedExecution, pushedChoice, conflictExecution, conflictChoice);
1128 pushedChoice = conflictChoice;
1129 pushedExecution = conflictExecution;
1131 // Continue performing DFS if conflict is not found
1132 updateBacktrackSetRecursive(execution, currentChoice, conflictExecution, conflictChoice,
1133 pushedExecution, pushedChoice, currRWSet, visited);
1137 // --- Functions related to the reachability analysis when there is a state match
1139 private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
1140 // Perform this analysis only when:
1141 // 1) this is not during a switch to a new execution,
1142 // 2) at least 2 choices/events have been explored (choiceCounter > 1),
1143 // 3) state > 0 (state 0 is for boolean CG)
1144 if (!isEndOfExecution && choiceCounter > 1 && stateId > 0) {
1145 if (currVisitedStates.contains(stateId)) {
1146 // Get the backtrack point from the current execution
1147 TransitionEvent transition = currentExecution.getTransitionFromState(stateId);
1148 transition.recordPredecessor(currentExecution, choiceCounter - 1);
1149 updateBacktrackSetsFromPreviousExecution(stateId);
1150 } else if (prevVisitedStates.contains(stateId)) { // We visit a state in a previous execution
1151 // Update past executions with a predecessor
1152 HashSet<TransitionEvent> reachableTransitions = rGraph.getReachableTransitionsAtState(stateId);
1153 for(TransitionEvent transition : reachableTransitions) {
1154 transition.recordPredecessor(currentExecution, choiceCounter - 1);
1156 updateBacktrackSetsFromPreviousExecution(stateId);
1161 // Update the backtrack sets from previous executions
1162 private void updateBacktrackSetsFromPreviousExecution(int stateId) {
1163 // Collect all the reachable transitions from R-Graph
1164 HashSet<TransitionEvent> reachableTransitions = rGraph.getReachableTransitions(stateId);
1165 for(TransitionEvent transition : reachableTransitions) {
1166 Execution execution = transition.getExecution();
1167 int currentChoice = transition.getChoiceCounter();
1168 updateBacktrackSet(execution, currentChoice);