// TODO: Fix for Groovy's model-checking
// TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
/**
- * simple tool to log state changes
+ * Simple tool to log state changes.
+ *
+ * This DPOR implementation is augmented by the algorithm presented in this SPIN paper:
+ * http://spinroot.com/spin/symposia/ws08/spin2008_submission_33.pdf
+ *
+ * The algorithm is presented on page 11 of the paper. Basically, we create a graph G
+ * (i.e., visible operation dependency graph)
+ * that maps inter-related threads/sub-programs that trigger state changes.
+ * The key to this approach is that we evaluate graph G in every iteration/recursion to
+ * only update the backtrack sets of the threads/sub-programs that are reachable in graph G
+ * from the currently running thread/sub-program.
*/
public class StateReducer extends ListenerAdapter {
private IntChoiceFromSet currCG;
private int choiceCounter;
private Integer choiceUpperBound;
+ private Integer maxUpperBound;
private boolean isInitialized;
private boolean isResetAfterAnalysis;
private boolean isBooleanCGFlipped;
- private HashMap<IntChoiceFromSet,Integer> cgMap;
+ private HashMap<IntChoiceFromSet, Integer> cgMap;
// Record the mapping between event number and field accesses (Read and Write)
- private HashMap<Integer,ReadWriteSet> readWriteFieldsMap;
+ private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
// The following is the backtrack map (set) that stores all the backtrack information
// e.g., event number 1 can have two backtrack sequences: {3,1,2,4,...} and {2,1,3,4,...}
- private HashMap<Integer,LinkedList<Integer[]>> backtrackMap;
- private HashMap<Integer,HashSet<Integer>> conflictPairMap;
+ private HashMap<Integer, LinkedList<Integer[]>> backtrackMap;
+ // Stores explored backtrack lists in the form of HashSet of Strings
+ private HashSet<String> backtrackSet;
+ private HashMap<Integer, HashSet<Integer>> conflictPairMap;
// Map choicelist with start index
- private HashMap<Integer[],Integer> choiceListStartIndexMap;
-
- public StateReducer (Config config, JPF jpf) {
+ // private HashMap<Integer[],Integer> choiceListStartIndexMap;
+
+ // Map that represents graph G
+ // (i.e., visible operation dependency graph (VOD Graph)
+ private HashMap<Integer, HashSet<Integer>> vodGraphMap;
+ // Set that represents hash table H
+ // (i.e., hash table that records encountered states)
+ // VOD graph is updated when the state has not yet been seen
+ private HashSet<Integer> visitedStateSet;
+ // Current state
+ private int stateId;
+ // Previous choice number
+ private int prevChoiceValue;
+
+ public StateReducer(Config config, JPF jpf) {
debugMode = config.getBoolean("debug_state_transition", false);
stateReductionMode = config.getBoolean("activate_state_reduction", true);
if (debugMode) {
id = 0;
transition = null;
isBooleanCGFlipped = false;
+ vodGraphMap = new HashMap<>();
+ visitedStateSet = new HashSet<>();
+ stateId = -1;
+ prevChoiceValue = -1;
initializeStateReduction();
}
currCG = null;
choiceCounter = 0;
choiceUpperBound = 0;
+ maxUpperBound = 0;
isInitialized = false;
isResetAfterAnalysis = false;
cgMap = new HashMap<>();
readWriteFieldsMap = new HashMap<>();
backtrackMap = new HashMap<>();
+ backtrackSet = new HashSet<>();
conflictPairMap = new HashMap<>();
- choiceListStartIndexMap = new HashMap<>();
}
}
}
@Override
- public void choiceGeneratorRegistered (VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
+ public void choiceGeneratorRegistered(VM vm, ChoiceGenerator<?> nextCG, ThreadInfo currentThread, Instruction executedInstruction) {
if (stateReductionMode) {
// Initialize with necessary information from the CG
if (nextCG instanceof IntChoiceFromSet) {
if (!isResetAfterAnalysis && choiceCounter <= choiceUpperBound && !cgMap.containsValue(choiceCounter)) {
// Update the choices of the first CG and add '-1'
if (choices == null) {
+ // Initialize backtrack set that stores all the explored backtrack lists
+ maxUpperBound = cgChoices.length;
// All the choices are always the same so we only need to update it once
choices = new Integer[cgChoices.length + 1];
System.arraycopy(cgChoices, 0, choices, 0, cgChoices.length);
choices[choices.length - 1] = -1;
+ String firstChoiceListString = buildStringFromChoiceList(choices);
+ backtrackSet.add(firstChoiceListString);
}
icsCG.setNewValues(choices);
icsCG.reset();
return;
}
// Reset every CG with the first backtrack lists
- for(IntChoiceFromSet cg : cgMap.keySet()) {
+ for (IntChoiceFromSet cg : cgMap.keySet()) {
int event = cgMap.get(cg);
LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
if (choiceLists != null && choiceLists.peekFirst() != null) {
}
@Override
- public void choiceGeneratorAdvanced (VM vm, ChoiceGenerator<?> currentCG) {
+ public void choiceGeneratorAdvanced(VM vm, ChoiceGenerator<?> currentCG) {
- if(stateReductionMode) {
+ if (stateReductionMode) {
// Check the boolean CG and if it is flipped, we are resetting the analysis
if (currentCG instanceof BooleanChoiceGenerator) {
if (!isBooleanCGFlipped) {
IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
// Update the current pointer to the current set of choices
if (choices == null || choices != icsCG.getAllChoices()) {
- choiceListStartIndexMap.remove(choices);
currCG = icsCG;
choices = icsCG.getAllChoices();
// Reset a few things for the sub-graph
- conflictPairMap = new HashMap<>();
- readWriteFieldsMap = new HashMap<>();
+ conflictPairMap.clear();
+ readWriteFieldsMap.clear();
choiceCounter = 0;
}
// Traverse the sub-graphs
// Advance choice counter for sub-graphs
choiceCounter++;
// Do this for every CG after finishing each backtrack list
- if (icsCG.getNextChoice() == -1) {
+ if (icsCG.getNextChoice() == -1 || visitedStateSet.contains(stateId)) {
int event = cgMap.get(icsCG);
LinkedList<Integer[]> choiceLists = backtrackMap.get(event);
if (choiceLists != null && choiceLists.peekFirst() != null) {
}
}
+ public void updateVODGraph(int prevChoice, int currChoice) {
+
+ HashSet<Integer> choiceSet;
+ if (vodGraphMap.containsKey(prevChoice)) {
+ // If the key already exists, just retrieve it
+ choiceSet = vodGraphMap.get(prevChoice);
+ } else {
+ // Create a new entry
+ choiceSet = new HashSet<>();
+ vodGraphMap.put(prevChoice, choiceSet);
+ }
+ choiceSet.add(currChoice);
+ }
+
@Override
public void stateAdvanced(Search search) {
if (debugMode) {
out.println("\n==> DEBUG: The state is forwarded to state with id: " + id + " with depth: " + depth +
" which is " + detail + " Transition: " + transition + "\n");
}
+ if (stateReductionMode) {
+ // Update vodGraph
+ int currChoice = choiceCounter - 1;
+ if (currChoice < 0 || choices[currChoice] == -1 || prevChoiceValue == choices[currChoice]) {
+ // Current choice has to be at least 0 (initial case can be -1)
+ return;
+ }
+ // When current choice is 0, previous choice could be -1
+ updateVODGraph(prevChoiceValue, choices[currChoice]);
+ // Current choice becomes previous choice in the next iteration
+ prevChoiceValue = choices[currChoice];
+ // Line 19 in the paper page 11 (see the heading note above)
+ stateId = search.getStateId();
+ // Add state ID into the visited state set
+ visitedStateSet.add(stateId);
+ }
}
@Override
// We store the field name and its object ID
// Sharing the same field means the same field name and object ID
private class ReadWriteSet {
- private HashMap<String,Integer> readSet;
- private HashMap<String,Integer> writeSet;
+ private HashMap<String, Integer> readSet;
+ private HashMap<String, Integer> writeSet;
public ReadWriteSet() {
readSet = new HashMap<>();
// Record the field in the map
if (executedInsn instanceof WriteInstruction) {
// Exclude certain field writes because of infrastructure needs, e.g., Event class field writes
- for(String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
+ for (String str : EXCLUDED_FIELDS_WRITE_INSTRUCTIONS_STARTS_WITH_LIST) {
if (fieldClass.startsWith(str)) {
return;
}
return true;
}
+ private String buildStringFromChoiceList(Integer[] newChoiceList) {
+
+ // When we see a choice list shorter than the upper bound, e.g., [3,2] for choices 0,1,2, and 3,
+ // then we have to pad the beginning before we store it, because [3,2] actually means [0,1,3,2]
+ // First, calculate the difference between this choice list and the upper bound
+ // The actual list doesn't include '-1' at the end
+ int actualListLength = newChoiceList.length - 1;
+ int diff = maxUpperBound - actualListLength;
+ StringBuilder sb = new StringBuilder();
+ // Pad the beginning if necessary
+ for (int i = 0; i < diff; i++) {
+ sb.append(i);
+ }
+ // Then continue with the actual choice list
+ // We don't include the '-1' at the end
+ for (int i = 0; i < newChoiceList.length - 1; i++) {
+ sb.append(newChoiceList[i]);
+ }
+ return sb.toString();
+ }
+
+ private void checkAndAddBacktrackList(LinkedList<Integer[]> backtrackChoiceLists, Integer[] newChoiceList) {
+
+ String newChoiceListString = buildStringFromChoiceList(newChoiceList);
+ // Add only if we haven't seen this combination before
+ if (!backtrackSet.contains(newChoiceListString)) {
+ backtrackSet.add(newChoiceListString);
+ backtrackChoiceLists.addLast(newChoiceList);
+ }
+ }
+
private void createBacktrackChoiceList(int currentChoice, int conflictEventNumber) {
LinkedList<Integer[]> backtrackChoiceLists;
}
// Set the last element to '-1' as the end of the sequence
newChoiceList[newChoiceList.length - 1] = -1;
- backtrackChoiceLists.addLast(newChoiceList);
+ checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
// The start index for the recursion is always 1 (from the main branch)
- choiceListStartIndexMap.put(newChoiceList, 1);
} else { // This is a sub-graph
- int backtrackListIndex = cgMap.get(currCG);
- backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
- int listLength = choices.length;
- Integer[] newChoiceList = new Integer[listLength];
- // Copy everything before the conflict number
- for(int i = 0; i < conflictEventNumber; i++) {
- newChoiceList[i] = choices[i];
- }
- // Put the conflicting events
- newChoiceList[conflictEventNumber] = choices[currentChoice];
- newChoiceList[conflictEventNumber + 1] = choices[conflictEventNumber];
- // Copy the rest
- for(int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
- if (choices[i] != choices[currentChoice]) {
- newChoiceList[j] = choices[i];
- j++;
+ // There is a case/bug that after a re-initialization, currCG is not yet initialized
+ if (currCG != null) {
+ int backtrackListIndex = cgMap.get(currCG);
+ backtrackChoiceLists = backtrackMap.get(backtrackListIndex);
+ int listLength = choices.length;
+ Integer[] newChoiceList = new Integer[listLength];
+ // Copy everything before the conflict number
+ for (int i = 0; i < conflictEventNumber; i++) {
+ newChoiceList[i] = choices[i];
+ }
+ // Put the conflicting events
+ newChoiceList[conflictEventNumber] = choices[currentChoice];
+ newChoiceList[conflictEventNumber + 1] = choices[conflictEventNumber];
+ // Copy the rest
+ for (int i = conflictEventNumber + 1, j = conflictEventNumber + 2; j < listLength - 1; i++) {
+ if (choices[i] != choices[currentChoice]) {
+ newChoiceList[j] = choices[i];
+ j++;
+ }
}
+ // Set the last element to '-1' as the end of the sequence
+ newChoiceList[newChoiceList.length - 1] = -1;
+ checkAndAddBacktrackList(backtrackChoiceLists, newChoiceList);
}
- // Set the last element to '-1' as the end of the sequence
- newChoiceList[newChoiceList.length - 1] = -1;
- backtrackChoiceLists.addLast(newChoiceList);
- // For the sub-graph the start index depends on the conflicting event number
- choiceListStartIndexMap.put(newChoiceList, conflictEventNumber + 1);
}
}
return false;
}
+ // This method checks whether a choice is reachable in the VOD graph from a reference choice
+ // This is a BFS search
+ private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
+ // Record visited choices as we search in the graph
+ HashSet<Integer> visitedChoice = new HashSet<>();
+ visitedChoice.add(referenceChoice);
+ LinkedList<Integer> nodesToVisit = new LinkedList<>();
+ // If the state doesn't advance as the threads/sub-programs are executed (basically there is no new state),
+ // there is a chance that the graph doesn't have new nodes---thus this check will return a null.
+ if (vodGraphMap.containsKey(referenceChoice)) {
+ nodesToVisit.addAll(vodGraphMap.get(referenceChoice));
+ while(!nodesToVisit.isEmpty()) {
+ int currChoice = nodesToVisit.getFirst();
+ if (currChoice == checkedChoice) {
+ return true;
+ }
+ if (visitedChoice.contains(currChoice)) {
+ // If there is a loop then we don't find it
+ return false;
+ }
+ // Continue searching
+ visitedChoice.add(currChoice);
+ HashSet<Integer> currChoiceNextNodes = vodGraphMap.get(currChoice);
+ if (currChoiceNextNodes != null) {
+ // Add only if there is a mapping for next nodes
+ for (Integer nextNode : currChoiceNextNodes) {
+ nodesToVisit.addLast(nextNode);
+ }
+ }
+ }
+ }
+ return false;
+ }
+
@Override
public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
if (stateReductionMode) {
String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
// We don't care about libraries
if (!isFieldExcluded(fieldClass)) {
- // For the main graph we go down to 0, but for subgraph, we only go down to 1 since 0 contains
- // the reversed event
- int end = !isResetAfterAnalysis ? 0 : choiceListStartIndexMap.get(choices);
// Check for conflict (go backward from currentChoice and get the first conflict)
// If the current event has conflicts with multiple events, then these will be detected
// one by one as this recursively checks backward when backtrack set is revisited and executed.
- for (int eventNumber = currentChoice - 1; eventNumber >= end; eventNumber--) {
+ for (int eventNumber = currentChoice - 1; eventNumber >= 0; eventNumber--) {
// Skip if this event number does not have any Read/Write set
if (!readWriteFieldsMap.containsKey(choices[eventNumber])) {
continue;
// We do not record and service the same backtrack pair/point twice!
// If it has been serviced before, we just skip this
if (recordConflictPair(currentChoice, eventNumber)) {
- createBacktrackChoiceList(currentChoice, eventNumber);
- // Break if a conflict is found!
- break;
+ // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
+ if (!visitedStateSet.contains(stateId)||
+ (visitedStateSet.contains(stateId) && isReachableInVODGraph(choices[currentChoice], choices[currentChoice-1]))) {
+ createBacktrackChoiceList(currentChoice, eventNumber);
+ // Break if a conflict is found!
+ break;
+ }
}
}
}
projects / jpf-core.git / blobdiff