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;
30 import java.io.PrintWriter;
34 // TODO: Fix for Groovy's model-checking
35 // TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
37 * Simple tool to log state changes.
39 * This DPOR implementation is augmented by the algorithm presented in this SPIN paper:
40 * http://spinroot.com/spin/symposia/ws08/spin2008_submission_33.pdf
42 * The algorithm is presented on page 11 of the paper. Basically, we create a graph G
43 * (i.e., visible operation dependency graph)
44 * that maps inter-related threads/sub-programs that trigger state changes.
45 * The key to this approach is that we evaluate graph G in every iteration/recursion to
46 * only update the backtrack sets of the threads/sub-programs that are reachable in graph G
47 * from the currently running thread/sub-program.
49 public class StateReducer extends ListenerAdapter {
52 private boolean debugMode;
53 private boolean stateReductionMode;
54 private final PrintWriter out;
55 volatile private String detail;
56 volatile private int depth;
57 volatile private int id;
58 Transition transition;
60 // State reduction fields
61 private Integer[] choices;
62 private IntChoiceFromSet currCG;
63 private int choiceCounter;
64 private Integer choiceUpperBound;
65 private Integer maxUpperBound;
66 private boolean isInitialized;
67 private boolean isResetAfterAnalysis;
68 private boolean isBooleanCGFlipped;
69 private HashMap<IntChoiceFromSet, Integer> cgMap;
70 // Record the mapping between event number and field accesses (Read and Write)
71 private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
72 // The following is the backtrack map (set) that stores all the backtrack information
73 // e.g., event number 1 can have two backtrack sequences: {3,1,2,4,...} and {2,1,3,4,...}
74 private HashMap<Integer, LinkedList<Integer[]>> backtrackMap;
75 // Stores explored backtrack lists in the form of HashSet of Strings
76 private HashSet<String> backtrackSet;
77 private HashMap<Integer, HashSet<Integer>> conflictPairMap;
78 // Map choicelist with start index
79 // private HashMap<Integer[],Integer> choiceListStartIndexMap;
81 // Map that represents graph G
82 // (i.e., visible operation dependency graph (VOD Graph)
83 private HashMap<Integer, HashSet<Integer>> vodGraphMap;
84 // Set that represents hash table H
85 // (i.e., hash table that records encountered states)
86 // VOD graph is updated when the state has not yet been seen
87 private HashSet<Integer> visitedStateSet;
90 // Previous choice number
91 private int prevChoiceValue;
93 public StateReducer(Config config, JPF jpf) {
94 debugMode = config.getBoolean("debug_state_transition", false);
95 stateReductionMode = config.getBoolean("activate_state_reduction", true);
97 out = new PrintWriter(System.out, true);
105 isBooleanCGFlipped = false;
106 vodGraphMap = new HashMap<>();
107 visitedStateSet = new HashSet<>();
109 prevChoiceValue = -1;
110 cgMap = new HashMap<>();
111 readWriteFieldsMap = new HashMap<>();
112 backtrackMap = new HashMap<>();
113 backtrackSet = new HashSet<>();
114 conflictPairMap = new HashMap<>();
115 initializeStateReduction();
118 private void initializeStateReduction() {
119 if (stateReductionMode) {
123 choiceUpperBound = 0;
125 isInitialized = false;
126 isResetAfterAnalysis = false;
128 readWriteFieldsMap.clear();
129 backtrackMap.clear();
130 backtrackSet.clear();
131 conflictPairMap.clear();
136 public void stateRestored(Search search) {
138 id = search.getStateId();
139 depth = search.getDepth();
140 transition = search.getTransition();
142 out.println("\n==> DEBUG: The state is restored to state with id: " + id + " -- Transition: " + transition +
143 " and depth: " + depth + "\n");
147 //--- the ones we are interested in
149 public void searchStarted(Search search) {
151 out.println("\n==> DEBUG: ----------------------------------- search started" + "\n");
156 public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
157 if (stateReductionMode) {
158 // Initialize with necessary information from the CG
159 if (nextCG instanceof IntChoiceFromSet) {
160 IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
161 // Check if CG has been initialized, otherwise initialize it
162 Integer[] cgChoices = icsCG.getAllChoices();
163 if (!isInitialized) {
164 // Get the upper bound from the last element of the choices
165 choiceUpperBound = cgChoices[cgChoices.length - 1];
166 isInitialized = true;
168 // Record the subsequent Integer CGs only until we hit the upper bound
169 if (!isResetAfterAnalysis && choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
170 // Update the choices of the first CG and add '-1'
171 if (choices == null) {
172 // Initialize backtrack set that stores all the explored backtrack lists
173 maxUpperBound = cgChoices.length;
174 // All the choices are always the same so we only need to update it once
175 choices = new Integer[cgChoices.length + 1];
176 System.arraycopy(cgChoices, 0, choices, 0, cgChoices.length);
177 choices[choices.length - 1] = -1;
178 String firstChoiceListString = buildStringFromChoiceList(choices);
179 backtrackSet.add(firstChoiceListString);
181 icsCG.setNewValues(choices);
183 // Advance the current Integer CG
184 // This way we explore all the event numbers in the first pass
185 icsCG.advance(choices[choiceCounter]);
186 cgMap.put(icsCG, choices[choiceCounter]);
189 // Set done the subsequent CGs
190 // We only need n CGs (n is event numbers)
197 private void resetAllCGs() {
198 // Extract the event numbers that have backtrack lists
199 Set<Integer> eventSet = backtrackMap.keySet();
200 // Return if there is no conflict at all (highly unlikely)
201 if (eventSet.isEmpty()) {
204 // Reset every CG with the first backtrack lists
205 for (IntChoiceFromSet cg : cgMap.keySet()) {
206 int event = cgMap.get(cg);
207 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
208 if (choiceLists != null && choiceLists.peekFirst() != null) {
209 Integer[] choiceList = choiceLists.removeFirst();
210 // Deploy the new choice list for this CG
211 cg.setNewValues(choiceList);
220 public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
222 if (stateReductionMode) {
223 // Check the boolean CG and if it is flipped, we are resetting the analysis
224 if (currentCG instanceof BooleanChoiceGenerator) {
225 if (!isBooleanCGFlipped) {
226 isBooleanCGFlipped = true;
228 initializeStateReduction();
231 // Check every choice generated and make sure that all the available choices
232 // are chosen first before repeating the same choice of value twice!
233 if (currentCG instanceof IntChoiceFromSet) {
234 IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
235 // Update the current pointer to the current set of choices
236 if (choices == null || choices != icsCG.getAllChoices()) {
238 choices = icsCG.getAllChoices();
239 // Reset a few things for the sub-graph
240 conflictPairMap.clear();
241 readWriteFieldsMap.clear();
244 // Traverse the sub-graphs
245 if (isResetAfterAnalysis) {
246 // Advance choice counter for sub-graphs
248 // Do this for every CG after finishing each backtrack list
249 if (icsCG.getNextChoice() == -1 || visitedStateSet.contains(stateId)) {
250 if (cgMap.containsKey(icsCG)) {
251 int event = cgMap.get(icsCG);
252 LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
253 if (choiceLists != null && choiceLists.peekFirst() != null) {
254 Integer[] choiceList = choiceLists.removeFirst();
255 // Deploy the new choice list for this CG
256 icsCG.setNewValues(choiceList);
259 // Set done if this was the last backtrack list
265 // Update and reset the CG if needed (do this for the first time after the analysis)
266 if (!isResetAfterAnalysis && icsCG.getNextChoice() == -1) {
268 isResetAfterAnalysis = true;
274 public void updateVODGraph(int prevChoice, int currChoice) {
276 HashSet<Integer> choiceSet;
277 if (vodGraphMap.containsKey(prevChoice)) {
278 // If the key already exists, just retrieve it
279 choiceSet = vodGraphMap.get(prevChoice);
281 // Create a new entry
282 choiceSet = new HashSet<>();
283 vodGraphMap.put(prevChoice, choiceSet);
285 choiceSet.add(currChoice);
289 public void stateAdvanced(Search search) {
291 id = search.getStateId();
292 depth = search.getDepth();
293 transition = search.getTransition();
294 if (search.isNewState()) {
300 if (search.isEndState()) {
301 out.println("\n==> DEBUG: This is the last state!\n");
304 out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
305 " which is " + detail + " Transition: " + transition + "\n");
307 if (stateReductionMode) {
309 int currChoice = choiceCounter - 1;
310 if (currChoice < 0 || currChoice > choices.length - 1 || choices[currChoice] == -1 || prevChoiceValue == choices[currChoice]) {
311 // Handle all corner cases (e.g., out of bound values)
314 // When current choice is 0, previous choice could be -1
315 updateVODGraph(prevChoiceValue, choices[currChoice]);
316 // Current choice becomes previous choice in the next iteration
317 prevChoiceValue = choices[currChoice];
318 // Line 19 in the paper page 11 (see the heading note above)
319 stateId = search.getStateId();
320 // Add state ID into the visited state set
321 visitedStateSet.add(stateId);
326 public void stateBacktracked(Search search) {
328 id = search.getStateId();
329 depth = search.getDepth();
330 transition = search.getTransition();
333 out.println("\n==> DEBUG: The state is backtracked to state with id: " + id + " -- Transition: " + transition +
334 " and depth: " + depth + "\n");
339 public void searchFinished(Search search) {
341 out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
345 // This class compactly stores Read and Write field sets
346 // We store the field name and its object ID
347 // Sharing the same field means the same field name and object ID
348 private class ReadWriteSet {
349 private HashMap<String, Integer> readSet;
350 private HashMap<String, Integer> writeSet;
352 public ReadWriteSet() {
353 readSet = new HashMap<>();
354 writeSet = new HashMap<>();
357 public void addReadField(String field, int objectId) {
358 readSet.put(field, objectId);
361 public void addWriteField(String field, int objectId) {
362 writeSet.put(field, objectId);
365 public boolean readFieldExists(String field) {
366 return readSet.containsKey(field);
369 public boolean writeFieldExists(String field) {
370 return writeSet.containsKey(field);
373 public int readFieldObjectId(String field) {
374 return readSet.get(field);
377 public int writeFieldObjectId(String field) {
378 return writeSet.get(field);
382 private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
383 // Do the analysis to get Read and Write accesses to fields
385 // We already have an entry
386 if (readWriteFieldsMap.containsKey(choices[currentChoice])) {
387 rwSet = readWriteFieldsMap.get(choices[currentChoice]);
388 } else { // We need to create a new entry
389 rwSet = new ReadWriteSet();
390 readWriteFieldsMap.put(choices[currentChoice], rwSet);
392 int objectId = ((JVMFieldInstruction) executedInsn).getFieldInfo().getClassInfo().getClassObjectRef();
393 // Record the field in the map
394 if (executedInsn instanceof WriteInstruction) {
395 // Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
396 for (String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
397 if (fieldClass.startsWith(str)) {
401 rwSet.addWriteField(fieldClass, objectId);
402 } else if (executedInsn instanceof ReadInstruction) {
403 rwSet.addReadField(fieldClass, objectId);
407 private boolean recordConflictPair(int currentEvent, int eventNumber) {
408 HashSet<Integer> conflictSet;
409 if (!conflictPairMap.containsKey(currentEvent)) {
410 conflictSet = new HashSet<>();
411 conflictPairMap.put(currentEvent, conflictSet);
413 conflictSet = conflictPairMap.get(currentEvent);
415 // If this conflict has been recorded before, we return false because
416 // we don't want to service this backtrack point twice
417 if (conflictSet.contains(eventNumber)) {
420 // If it hasn't been recorded, then do otherwise
421 conflictSet.add(eventNumber);
425 private String buildStringFromChoiceList(Integer[] newChoiceList) {
427 // When we see a choice list shorter than the upper bound, e.g., [3,2] for choices 0,1,2, and 3,
428 // then we have to pad the beginning before we store it, because [3,2] actually means [0,1,3,2]
429 // First, calculate the difference between this choice list and the upper bound
430 // The actual list doesn't include '-1' at the end
431 int actualListLength = newChoiceList.length - 1;
432 int diff = maxUpperBound - actualListLength;
433 StringBuilder sb = new StringBuilder();
434 // Pad the beginning if necessary
435 for (int i = 0; i < diff; i++) {
438 // Then continue with the actual choice list
439 // We don't include the '-1' at the end
440 for (int i = 0; i < newChoiceList.length - 1; i++) {
441 sb.append(newChoiceList[i]);
443 return sb.toString();
446 private void checkAndAddBacktrackList(LinkedList<Integer[]> backtrackChoiceLists, Integer[] newChoiceList) {
448 String newChoiceListString = buildStringFromChoiceList(newChoiceList);
449 // Add only if we haven't seen this combination before
450 if (!backtrackSet.contains(newChoiceListString)) {
451 backtrackSet.add(newChoiceListString);
452 backtrackChoiceLists.addLast(newChoiceList);
456 private void createBacktrackChoiceList(int currentChoice, int conflictEventNumber) {
458 LinkedList<Integer[]> backtrackChoiceLists;
459 // Create a new list of choices for backtrack based on the current choice and conflicting event number
460 // If we have a conflict between 1 and 3, then we create the list {3, 1, 2, 4, 5} for backtrack
461 // The backtrack point is the CG for event number 1 and the list length is one less than the original list
462 // (originally of length 6) since we don't start from event number 0
463 if (!isResetAfterAnalysis) {
464 // Check if we have a list for this choice number
465 // If not we create a new one for it
466 if (!backtrackMap.containsKey(conflictEventNumber)) {
467 backtrackChoiceLists = new LinkedList<>();
468 backtrackMap.put(conflictEventNumber, backtrackChoiceLists);
470 backtrackChoiceLists = backtrackMap.get(conflictEventNumber);
472 int maxListLength = choiceUpperBound + 1;
473 int listLength = maxListLength - conflictEventNumber;
474 Integer[] newChoiceList = new Integer[listLength + 1];
475 // Put the conflicting event numbers first and reverse the order
476 newChoiceList[0] = choices[currentChoice];
477 newChoiceList[1] = choices[conflictEventNumber];
478 // Put the rest of the event numbers into the array starting from the minimum to the upper bound
479 for (int i = conflictEventNumber + 1, j = 2; j < listLength; i++) {
480 if (choices[i] != choices[currentChoice]) {
481 newChoiceList[j] = choices[i];
485 // Set the last element to '-1' as the end of the sequence
486 newChoiceList[newChoiceList.length - 1] = -1;
487 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
488 // The start index for the recursion is always 1 (from the main branch)
489 } else { // This is a sub-graph
490 // There is a case/bug that after a re-initialization, currCG is not yet initialized
491 if (currCG != null && cgMap.containsKey(currCG)) {
492 int backtrackListIndex = cgMap.get(currCG);
493 backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
494 int listLength = choices.length;
495 Integer[] newChoiceList = new Integer[listLength];
496 // Copy everything before the conflict number
497 for (int i = 0; i < conflictEventNumber; i++) {
498 newChoiceList[i] = choices[i];
500 // Put the conflicting events
501 newChoiceList[conflictEventNumber] = choices[currentChoice];
502 newChoiceList[conflictEventNumber + 1] = choices[conflictEventNumber];
504 for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
505 if (choices[i] != choices[currentChoice]) {
506 newChoiceList[j] = choices[i];
510 // Set the last element to '-1' as the end of the sequence
511 newChoiceList[newChoiceList.length - 1] = -1;
512 checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
517 // We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
518 private final static String[] EXCLUDED_FIELDS_STARTS_WITH_LIST =
519 // Java and Groovy libraries
520 { "java", "org", "sun", "com", "gov", "groovy"};
521 private final static String[] EXCLUDED_FIELDS_ENDS_WITH_LIST =
522 // Groovy library created fields
523 {"stMC", "callSiteArray", "metaClass", "staticClassInfo", "__constructor__",
525 "sendEvent", "Object", "reference", "location", "app", "state", "log", "functionList", "objectList",
526 "eventList", "valueList", "settings", "printToConsole", "app1", "app2"};
527 private final static String[] EXCLUDED_FIELDS_CONTAINS_LIST = {"_closure"};
528 private final static String[] EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST = {"Event"};
530 private boolean isFieldExcluded(String field) {
531 // Check against "starts-with" list
532 for(String str : EXCLUDED_FIELDS_STARTS_WITH_LIST) {
533 if (field.startsWith(str)) {
537 // Check against "ends-with" list
538 for(String str : EXCLUDED_FIELDS_ENDS_WITH_LIST) {
539 if (field.endsWith(str)) {
543 // Check against "contains" list
544 for(String str : EXCLUDED_FIELDS_CONTAINS_LIST) {
545 if (field.contains(str)) {
553 // This method checks whether a choice is reachable in the VOD graph from a reference choice
554 // This is a BFS search
555 private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
556 // Record visited choices as we search in the graph
557 HashSet<Integer> visitedChoice = new HashSet<>();
558 visitedChoice.add(referenceChoice);
559 LinkedList<Integer> nodesToVisit = new LinkedList<>();
560 // If the state doesn't advance as the threads/sub-programs are executed (basically there is no new state),
561 // there is a chance that the graph doesn't have new nodes---thus this check will return a null.
562 if (vodGraphMap.containsKey(referenceChoice)) {
563 nodesToVisit.addAll(vodGraphMap.get(referenceChoice));
564 while(!nodesToVisit.isEmpty()) {
565 int currChoice = nodesToVisit.getFirst();
566 if (currChoice == checkedChoice) {
569 if (visitedChoice.contains(currChoice)) {
570 // If there is a loop then we don't find it
573 // Continue searching
574 visitedChoice.add(currChoice);
575 HashSet<Integer> currChoiceNextNodes = vodGraphMap.get(currChoice);
576 if (currChoiceNextNodes != null) {
577 // Add only if there is a mapping for next nodes
578 for (Integer nextNode : currChoiceNextNodes) {
579 nodesToVisit.addLast(nextNode);
588 public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
589 if (stateReductionMode) {
591 if (choiceCounter > choices.length - 1) {
592 // We do not compute the conflicts for the choice '-1'
595 int currentChoice = choiceCounter - 1;
596 // Record accesses from executed instructions
597 if (executedInsn instanceof JVMFieldInstruction) {
598 // Analyze only after being initialized
599 String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
600 // We don't care about libraries
601 if (!isFieldExcluded(fieldClass)) {
602 analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
605 // Analyze conflicts from next instructions
606 if (nextInsn instanceof JVMFieldInstruction) {
607 // The constructor is only called once when the object is initialized
608 // It does not have shared access with other objects
609 MethodInfo mi = nextInsn.getMethodInfo();
610 if (!mi.getName().equals("<init>")) {
611 String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
612 // We don't care about libraries
613 if (!isFieldExcluded(fieldClass)) {
614 // Check for conflict (go backward from currentChoice and get the first conflict)
615 // If the current event has conflicts with multiple events, then these will be detected
616 // one by one as this recursively checks backward when backtrack set is revisited and executed.
617 for (int eventNumber = currentChoice - 1; eventNumber >= 0; eventNumber--) {
618 // Skip if this event number does not have any Read/Write set
619 if (!readWriteFieldsMap.containsKey(choices[eventNumber])) {
622 ReadWriteSet rwSet = readWriteFieldsMap.get(choices[eventNumber]);
623 int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
624 // 1) Check for conflicts with Write fields for both Read and Write instructions
625 if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
626 rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
627 (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
628 rwSet.readFieldObjectId(fieldClass) == currObjId)) {
629 // We do not record and service the same backtrack pair/point twice!
630 // If it has been serviced before, we just skip this
631 if (recordConflictPair(currentChoice, eventNumber)) {
632 // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
633 if (!visitedStateSet.contains(stateId)||
634 (visitedStateSet.contains(stateId) && isReachableInVODGraph(choices[currentChoice], choices[currentChoice-1]))) {
635 createBacktrackChoiceList(currentChoice, eventNumber);
636 // Break if a conflict is found!