import gov.nasa.jpf.vm.choice.IntChoiceFromSet;
import gov.nasa.jpf.vm.choice.IntIntervalGenerator;
+import java.io.FileWriter;
import java.io.PrintWriter;
import java.util.*;
+import java.util.logging.Logger;
+import java.io.IOException;
// TODO: Fix for Groovy's model-checking
// TODO: This is a setter to change the values of the ChoiceGenerator to implement POR
* 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.
+ * The algorithm is presented on page 11 of the paper. Basically, we have a graph G
+ * (i.e., visible operation dependency graph).
+ * This DPOR implementation actually fixes the algorithm in the SPIN paper that does not
+ * consider cases where a state could be matched early. In this new algorithm/implementation,
+ * each run is terminated iff:
+ * - we find a state that matches a state in a previous run, or
+ * - we have a matched state in the current run that consists of cycles that contain all choices/events.
*/
public class DPORStateReducer extends ListenerAdapter {
private boolean verboseMode;
private boolean stateReductionMode;
private final PrintWriter out;
+ private PrintWriter fileWriter;
private String detail;
private int depth;
private int id;
// DPOR-related fields
// Basic information
private Integer[] choices;
- private Integer[] refChoices;
+ private Integer[] refChoices; // Second reference to a copy of choices (choices may be modified for fair scheduling)
private int choiceCounter;
private int maxEventChoice;
// Data structure to track the events seen by each state to track cycles (containing all events) for termination
private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
private HashMap<Integer, HashSet<Integer>> stateToEventMap;
// Data structure to analyze field Read/Write accesses and conflicts
- private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
- private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
- private ArrayList<IntChoiceFromSet> cgList; // Record CGs for backtracking points
- private HashMap<Integer, IntChoiceFromSet> cgMap; // Maps state IDs to CGs
- private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
-// private HashSet<IntChoiceFromSet> activeBacktrackCGs; // Record active backtrack CGs
- private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
-
- // Visible operation dependency graph implementation (SPIN paper) related fields
- private int prevChoiceValue;
- private HashMap<Integer, HashSet<Integer>> vodGraphMap; // Visible operation dependency graph (VOD graph)
+ private HashMap<Integer, LinkedList<Integer[]>> backtrackMap; // Track created backtracking points
+ private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
+ private ArrayList<BacktrackPoint> backtrackPointList; // Record backtrack points (CG, state Id, and choice)
+ private HashMap<Integer, HashSet<Integer>> conflictPairMap; // Record conflicting events
+ private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
+ private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
+ private HashMap<Integer, RestorableVMState> restorableStateMap; // Maps state IDs to the restorable state object
+ private HashMap<Integer, Integer> stateToChoiceCounterMap; // Maps state IDs to the choice counter
+ private HashMap<Integer, ArrayList<ReachableTrace>> rGraph; // Create a reachability graph
// Boolean states
private boolean isBooleanCGFlipped;
- private boolean isFirstResetDone;
private boolean isEndOfExecution;
+ // Statistics
+ private int numOfConflicts;
+ private int numOfTransitions;
+
public DPORStateReducer(Config config, JPF jpf) {
verboseMode = config.getBoolean("printout_state_transition", false);
stateReductionMode = config.getBoolean("activate_state_reduction", true);
} else {
out = null;
}
- // DPOR-related
- choices = null;
- refChoices = null;
- choiceCounter = 0;
- maxEventChoice = 0;
- // Cycle tracking
- currVisitedStates = new HashSet<>();
- justVisitedStates = new HashSet<>();
- prevVisitedStates = new HashSet<>();
- stateToEventMap = new HashMap<>();
- // Backtracking
- backtrackMap = new HashMap<>();
- backtrackStateQ = new PriorityQueue<>();
- cgList = new ArrayList<>();
- cgMap = new HashMap<>();
- conflictPairMap = new HashMap<>();
-// activeBacktrackCGs = new HashSet<>();
- readWriteFieldsMap = new HashMap<>();
- // VOD graph
- prevChoiceValue = -1;
- vodGraphMap = new HashMap<>();
- // Booleans
+ String outputFile = config.getString("file_output");
+ if (!outputFile.isEmpty()) {
+ try {
+ fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
+ } catch (IOException e) {
+ }
+ }
isBooleanCGFlipped = false;
- isEndOfExecution = false;
- isFirstResetDone = false;
+ numOfConflicts = 0;
+ numOfTransitions = 0;
+ restorableStateMap = new HashMap<>();
+ initializeStatesVariables();
}
@Override
}
}
+ static Logger log = JPF.getLogger("report");
+
@Override
public void searchFinished(Search search) {
+ if (stateReductionMode) {
+ // Number of conflicts = first trace + subsequent backtrack points
+ numOfConflicts += 1 + doneBacktrackSet.size();
+ }
if (verboseMode) {
+ out.println("\n==> DEBUG: ----------------------------------- search finished");
+ out.println("\n==> DEBUG: State reduction mode : " + stateReductionMode);
+ out.println("\n==> DEBUG: Number of conflicts : " + numOfConflicts);
+ out.println("\n==> DEBUG: Number of transitions : " + numOfTransitions);
out.println("\n==> DEBUG: ----------------------------------- search finished" + "\n");
+
+ fileWriter.println("==> DEBUG: State reduction mode : " + stateReductionMode);
+ fileWriter.println("==> DEBUG: Number of conflicts : " + numOfConflicts);
+ fileWriter.println("==> DEBUG: Number of transitions : " + numOfTransitions);
+ fileWriter.println();
+ fileWriter.close();
}
}
// Use a modulo since choiceCounter is going to keep increasing
int choiceIndex = choiceCounter % choices.length;
icsCG.advance(choices[choiceIndex]);
- // Index the ChoiceGenerator to set backtracking points
- cgList.add(icsCG);
} else {
// Set done all CGs while transitioning to a new execution
icsCG.setDone();
if (stateReductionMode) {
// Check the boolean CG and if it is flipped, we are resetting the analysis
-// if (currentCG instanceof BooleanChoiceGenerator) {
-// if (!isBooleanCGFlipped) {
-// isBooleanCGFlipped = true;
-// } else {
-// initializeStateReduction();
-// }
-// }
+ if (currentCG instanceof BooleanChoiceGenerator) {
+ if (!isBooleanCGFlipped) {
+ isBooleanCGFlipped = true;
+ } else {
+ // Number of conflicts = first trace + subsequent backtrack points
+ numOfConflicts = 1 + doneBacktrackSet.size();
+ // Allocate new objects for data structure when the boolean is flipped from "false" to "true"
+ initializeStatesVariables();
+ }
+ }
// Check every choice generated and ensure fair scheduling!
if (currentCG instanceof IntChoiceFromSet) {
IntChoiceFromSet icsCG = (IntChoiceFromSet) currentCG;
// If this is a new CG then we need to update data structures
- resetStatesForNewExecution(icsCG);
+ resetStatesForNewExecution(icsCG, vm);
// If we don't see a fair scheduling of events/choices then we have to enforce it
- checkAndEnforceFairScheduling(icsCG);
+ fairSchedulingAndBacktrackPoint(icsCG, vm);
+ // Explore the next backtrack point:
+ // 1) if we have seen this state or this state contains cycles that involve all events, and
+ // 2) after the current CG is advanced at least once
+ if (terminateCurrentExecution() && choiceCounter > 0) {
+ exploreNextBacktrackPoints(vm, icsCG);
+ } else {
+ numOfTransitions++;
+ }
// Map state to event
mapStateToEvent(icsCG.getNextChoice());
- // Update the VOD graph always with the latest
- updateVODGraph(icsCG.getNextChoice());
- // Check if we have seen this state or this state contains cycles that involve all events
- if (terminateCurrentExecution()) {
- exploreNextBacktrackPoints(icsCG, vm);
- }
justVisitedStates.clear();
choiceCounter++;
}
+ } else {
+ numOfTransitions++;
}
}
// Check and record a backtrack set for just once!
if (isConflictFound(nextInsn, eventCounter, currentChoice, fieldClass) &&
isNewConflict(currentChoice, eventCounter)) {
- // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
- if (vm.isNewState() || isReachableInVODGraph(currentChoice)) {
- createBacktrackingPoint(currentChoice, eventCounter);
- }
+ createBacktrackingPoint(currentChoice, eventCounter, false);
}
}
}
writeSet.put(field, objectId);
}
+ public Set<String> getReadSet() {
+ return readSet.keySet();
+ }
+
+ public Set<String> getWriteSet() {
+ return writeSet.keySet();
+ }
+
public boolean readFieldExists(String field) {
return readSet.containsKey(field);
}
}
}
- // This class compactly stores backtracking points: 1) backtracking ChoiceGenerator, and 2) backtracking choices
+ // This class compactly stores backtrack points: 1) backtrack state ID, and 2) backtracking choices
private class BacktrackPoint {
- private IntChoiceFromSet backtrackCG; // CG to backtrack from
- private Integer[] backtrackChoices; // Choices to set for this backtrack CG
+ private IntChoiceFromSet backtrackCG; // CG at this backtrack point
+ private int stateId; // State at this backtrack point
+ private int choice; // Choice chosen at this backtrack point
- public BacktrackPoint(IntChoiceFromSet cg, Integer[] choices) {
+ public BacktrackPoint(IntChoiceFromSet cg, int stId, int cho) {
backtrackCG = cg;
- backtrackChoices = choices;
+ stateId = stId;
+ choice = cho;
+ }
+
+ public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
+
+ public int getStateId() {
+ return stateId;
+ }
+
+ public int getChoice() {
+ return choice;
}
+ }
+
+ // This class stores a compact representation of a reachability graph for past executions
+ private class ReachableTrace {
+ private ArrayList<BacktrackPoint> pastBacktrackPointList;
+ private HashMap<Integer, ReadWriteSet> pastReadWriteFieldsMap;
- public IntChoiceFromSet getBacktrackCG() {
- return backtrackCG;
+ public ReachableTrace(ArrayList<BacktrackPoint> btrackPointList,
+ HashMap<Integer, ReadWriteSet> rwFieldsMap) {
+ pastBacktrackPointList = btrackPointList;
+ pastReadWriteFieldsMap = rwFieldsMap;
}
- public Integer[] getBacktrackChoices() {
- return backtrackChoices;
+ public ArrayList<BacktrackPoint> getPastBacktrackPointList() {
+ return pastBacktrackPointList;
+ }
+
+ public HashMap<Integer, ReadWriteSet> getPastReadWriteFieldsMap() {
+ return pastReadWriteFieldsMap;
}
}
private final static String JAVA_STRING_LIB = "java.lang.String";
// -- FUNCTIONS
- private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
+ private void fairSchedulingAndBacktrackPoint(IntChoiceFromSet icsCG, VM vm) {
// Check the next choice and if the value is not the same as the expected then force the expected value
int choiceIndex = choiceCounter % refChoices.length;
int nextChoice = icsCG.getNextChoice();
icsCG.setChoice(currCGIndex, expectedChoice);
}
}
+ // Record state ID and choice/event as backtrack point
+ int stateId = vm.getStateId();
+ backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex]));
+ // Store restorable state object for this state (always store the latest)
+ RestorableVMState restorableState = vm.getRestorableState();
+ restorableStateMap.put(stateId, restorableState);
}
private Integer[] copyChoices(Integer[] choicesToCopy) {
return true;
}
+ private void initializeStatesVariables() {
+ // DPOR-related
+ choices = null;
+ refChoices = null;
+ choiceCounter = 0;
+ maxEventChoice = 0;
+ // Cycle tracking
+ currVisitedStates = new HashSet<>();
+ justVisitedStates = new HashSet<>();
+ prevVisitedStates = new HashSet<>();
+ stateToEventMap = new HashMap<>();
+ // Backtracking
+ backtrackMap = new HashMap<>();
+ backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
+ backtrackPointList = new ArrayList<>();
+ conflictPairMap = new HashMap<>();
+ doneBacktrackSet = new HashSet<>();
+ readWriteFieldsMap = new HashMap<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ rGraph = new HashMap<>();
+ // Booleans
+ isEndOfExecution = false;
+ }
+
private void mapStateToEvent(int nextChoiceValue) {
// Update all states with this event/choice
// This means that all past states now see this transition
// Update the state variables
// Line 19 in the paper page 11 (see the heading note above)
int stateId = search.getStateId();
- currVisitedStates.add(stateId);
// Insert state ID into the map if it is new
if (!stateToEventMap.containsKey(stateId)) {
HashSet<Integer> eventSet = new HashSet<>();
stateToEventMap.put(stateId, eventSet);
}
+ // Save execution state into the Reachability only if
+ // (1) It is not a revisited state from a past execution, or
+ // (2) It is just a new backtracking point
+ if (!prevVisitedStates.contains(stateId) ||
+ choiceCounter <= 1) {
+ ReachableTrace reachableTrace= new
+ ReachableTrace(backtrackPointList, readWriteFieldsMap);
+ ArrayList<ReachableTrace> rTrace;
+ if (!prevVisitedStates.contains(stateId)) {
+ rTrace = new ArrayList<>();
+ rGraph.put(stateId, rTrace);
+ } else {
+ rTrace = rGraph.get(stateId);
+ }
+ rTrace.add(reachableTrace);
+ }
+ stateToChoiceCounterMap.put(stateId, choiceCounter);
+ analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
justVisitedStates.add(stateId);
+ currVisitedStates.add(stateId);
}
// --- Functions related to Read/Write access analysis on shared fields
- private void addNewBacktrackPoint(IntChoiceFromSet backtrackCG, Integer[] newChoiceList) {
- int stateId = backtrackCG.getStateId();
+ private void addNewBacktrackPoint(int stateId, Integer[] newChoiceList) {
// Insert backtrack point to the right state ID
LinkedList<Integer[]> backtrackList;
if (backtrackMap.containsKey(stateId)) {
backtrackList = backtrackMap.get(stateId);
} else {
backtrackList = new LinkedList<>();
+ backtrackMap.put(stateId, backtrackList);
}
backtrackList.addFirst(newChoiceList);
- // Add CG for this state ID if there isn't one yet
- if (!cgMap.containsKey(stateId)) {
- cgMap.put(stateId, backtrackCG);
- }
// Add to priority queue
if (!backtrackStateQ.contains(stateId)) {
backtrackStateQ.add(stateId);
// If current choice is not the same, then this is caused by the firing of IntIntervalGenerator
// for certain method calls in the infrastructure, e.g., eventSince()
int currChoiceInd = currentChoice % refChoices.length;
- int currChoiceFromCG = getCurrentChoice(vm);
+ int currChoiceFromCG = currChoiceInd;
+ ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
+ // This is the main event CG
+ if (currentCG instanceof IntIntervalGenerator) {
+ // This is the interval CG used in device handlers
+ ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
+ // Iterate until we find the IntChoiceFromSet CG
+ while (!(parentCG instanceof IntChoiceFromSet)) {
+ parentCG = ((IntIntervalGenerator) parentCG).getPreviousChoiceGenerator();
+ }
+ int actualEvtNum = ((IntChoiceFromSet) parentCG).getNextChoice();
+ // Find the index of the event/choice in refChoices
+ for (int i = 0; i<refChoices.length; i++) {
+ if (actualEvtNum == refChoices[i]) {
+ currChoiceFromCG = i;
+ break;
+ }
+ }
+ }
if (currChoiceInd != currChoiceFromCG) {
currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
}
return currentChoice;
}
- private void createBacktrackingPoint(int currentChoice, int confEvtNum) {
+ private void createBacktrackingPoint(int currentChoice, int confEvtNum, boolean isPastTrace) {
// Create a new list of choices for backtrack based on the current choice and conflicting event number
// E.g. if we have a conflict between 1 and 3, then we create the list {3, 1, 0, 2}
// for the original set {0, 1, 2, 3}
Integer[] newChoiceList = new Integer[refChoices.length];
// Put the conflicting event numbers first and reverse the order
- int actualCurrCho = currentChoice % refChoices.length;
- int actualConfEvtNum = confEvtNum % refChoices.length;
- newChoiceList[0] = refChoices[actualCurrCho];
- newChoiceList[1] = refChoices[actualConfEvtNum];
+ if (isPastTrace) {
+ // For past trace we get the choice/event from the list
+ newChoiceList[0] = backtrackPointList.get(currentChoice).getChoice();
+ } else {
+ // We use the actual choices here in case they have been modified/adjusted by the fair scheduling method
+ int actualCurrCho = currentChoice % refChoices.length;
+ newChoiceList[0] = choices[actualCurrCho];
+ }
+ newChoiceList[1] = backtrackPointList.get(confEvtNum).getChoice();
// Put the rest of the event numbers into the array starting from the minimum to the upper bound
for (int i = 0, j = 2; i < refChoices.length; i++) {
if (refChoices[i] != newChoiceList[0] && refChoices[i] != newChoiceList[1]) {
j++;
}
}
- // Record the backtracking point in the stack as well
- IntChoiceFromSet backtrackCG = cgList.get(confEvtNum);
- //BacktrackPoint backtrackPoint = new BacktrackPoint(backtrackCG, newChoiceList);
- addNewBacktrackPoint(backtrackCG, newChoiceList);
+ // Get the backtrack CG for this backtrack point
+ int stateId = backtrackPointList.get(confEvtNum).getStateId();
+ // Check if this trace has been done starting from this state
+ if (isTraceAlreadyConstructed(newChoiceList, stateId)) {
+ return;
+ }
+ addNewBacktrackPoint(stateId, newChoiceList);
}
private boolean excludeThisForItContains(String[] excludedStrings, String className) {
return false;
}
- private void exploreNextBacktrackPoints(IntChoiceFromSet icsCG, VM vm) {
- // We can start exploring the next backtrack point after the current CG is advanced at least once
- if (icsCG.getNextChoiceIndex() > 0) {
- if (backtrackMap.isEmpty()) {
- // This means we are reaching the end of our execution: no more backtracking points to explore
- return;
- }
- setNextBacktrackPoint(icsCG);
- // Save all the visited states when starting a new execution of trace
- prevVisitedStates.addAll(currVisitedStates);
- currVisitedStates.clear();
- // This marks a transitional period to the new CG
- isEndOfExecution = true;
- }
- }
-
- private int getCurrentChoice(VM vm) {
- ChoiceGenerator<?> currentCG = vm.getChoiceGenerator();
- // This is the main event CG
- if (currentCG instanceof IntChoiceFromSet) {
- return ((IntChoiceFromSet) currentCG).getNextChoiceIndex();
- } else {
- // This is the interval CG used in device handlers
- ChoiceGenerator<?> parentCG = ((IntIntervalGenerator) currentCG).getPreviousChoiceGenerator();
- return ((IntChoiceFromSet) parentCG).getNextChoiceIndex();
- }
+ private void exploreNextBacktrackPoints(VM vm, IntChoiceFromSet icsCG) {
+
+ // Check if we are reaching the end of our execution: no more backtracking points to explore
+ // cgMap, backtrackMap, backtrackStateQ are updated simultaneously (checking backtrackStateQ is enough)
+ if (!backtrackStateQ.isEmpty()) {
+ // Set done all the other backtrack points
+ for (BacktrackPoint backtrackPoint : backtrackPointList) {
+ backtrackPoint.getBacktrackCG().setDone();
+ }
+ // Reset the next backtrack point with the latest state
+ int hiStateId = backtrackStateQ.peek();
+ // Restore the state first if necessary
+ if (vm.getStateId() != hiStateId) {
+ RestorableVMState restorableState = restorableStateMap.get(hiStateId);
+ vm.restoreState(restorableState);
+ }
+ // Set the backtrack CG
+ IntChoiceFromSet backtrackCG = (IntChoiceFromSet) vm.getChoiceGenerator();
+ setBacktrackCG(hiStateId, backtrackCG);
+ } else {
+ // Set done this last CG (we save a few rounds)
+ icsCG.setDone();
+ }
+ // Save all the visited states when starting a new execution of trace
+ prevVisitedStates.addAll(currVisitedStates);
+ currVisitedStates.clear();
+ // This marks a transitional period to the new CG
+ isEndOfExecution = true;
}
private ReadWriteSet getReadWriteSet(int currentChoice) {
return rwSet;
}
+ private boolean isConflictFound(int eventCounter, int currentChoice, boolean isPastTrace) {
+
+ int currActualChoice;
+ if (isPastTrace) {
+ currActualChoice = backtrackPointList.get(currentChoice).getChoice();
+ } else {
+ int actualCurrCho = currentChoice % refChoices.length;
+ currActualChoice = choices[actualCurrCho];
+ }
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!readWriteFieldsMap.containsKey(eventCounter) ||
+ currActualChoice == backtrackPointList.get(eventCounter).getChoice()) {
+ return false;
+ }
+ // Current R/W set
+ ReadWriteSet currRWSet = readWriteFieldsMap.get(currentChoice);
+ // R/W set of choice/event that may have a potential conflict
+ ReadWriteSet evtRWSet = readWriteFieldsMap.get(eventCounter);
+ // Check for conflicts with Read and Write fields for Write instructions
+ Set<String> currWriteSet = currRWSet.getWriteSet();
+ for(String writeField : currWriteSet) {
+ int currObjId = currRWSet.writeFieldObjectId(writeField);
+ if ((evtRWSet.readFieldExists(writeField) && evtRWSet.readFieldObjectId(writeField) == currObjId) ||
+ (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId)) {
+ return true;
+ }
+ }
+ // Check for conflicts with Write fields for Read instructions
+ Set<String> currReadSet = currRWSet.getReadSet();
+ for(String readField : currReadSet) {
+ int currObjId = currRWSet.readFieldObjectId(readField);
+ if (evtRWSet.writeFieldExists(readField) && evtRWSet.writeFieldObjectId(readField) == currObjId) {
+ return true;
+ }
+ }
+ // Return false if no conflict is found
+ return false;
+ }
+
private boolean isConflictFound(Instruction nextInsn, int eventCounter, int currentChoice, String fieldClass) {
- int actualEvtCntr = eventCounter % refChoices.length;
+
int actualCurrCho = currentChoice % refChoices.length;
// Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
- if (!readWriteFieldsMap.containsKey(eventCounter) || (actualEvtCntr == actualCurrCho)) {
+ if (!readWriteFieldsMap.containsKey(eventCounter) ||
+ choices[actualCurrCho] == backtrackPointList.get(eventCounter).getChoice()) {
return false;
}
ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
return true;
}
- private void resetStatesForNewExecution(IntChoiceFromSet icsCG) {
+ private boolean isTraceAlreadyConstructed(Integer[] choiceList, int stateId) {
+ // Concatenate state ID and only the first event in the string, e.g., "1:1 for the trace 10234 at state 1"
+ // TODO: THIS IS AN OPTIMIZATION!
+ // This is the optimized version because after we execute, e.g., the trace 1:10234, we don't need to try
+ // another trace that starts with event 1 at state 1, e.g., the trace 1:13024
+ // The second time this event 1 is explored, it will generate the same state as the first one
+ StringBuilder sb = new StringBuilder();
+ sb.append(stateId);
+ sb.append(':');
+ sb.append(choiceList[0]);
+ // Check if the trace has been constructed as a backtrack point for this state
+ if (doneBacktrackSet.contains(sb.toString())) {
+ return true;
+ }
+ doneBacktrackSet.add(sb.toString());
+ return false;
+ }
+
+ private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
if (choices == null || choices != icsCG.getAllChoices()) {
// Reset state variables
- choiceCounter = 1;
+ choiceCounter = 0;
choices = icsCG.getAllChoices();
refChoices = copyChoices(choices);
- // Clearing data structures
- backtrackMap.clear();
- conflictPairMap.clear();
- readWriteFieldsMap.clear();
- stateToEventMap.clear();
+ // Clear data structures
+ backtrackPointList = new ArrayList<>();
+ conflictPairMap = new HashMap<>();
+ readWriteFieldsMap = new HashMap<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ stateToEventMap = new HashMap<>();
isEndOfExecution = false;
- // Adding this CG as the first CG for this execution
- cgList.add(icsCG);
}
}
- private IntChoiceFromSet setBacktrackCG(int stateId) {
+ private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
// Set a backtrack CG based on a state ID
- IntChoiceFromSet backtrackCG = cgMap.get(stateId);
LinkedList<Integer[]> backtrackChoices = backtrackMap.get(stateId);
backtrackCG.setNewValues(backtrackChoices.removeLast()); // Get the last from the queue
+ backtrackCG.setStateId(stateId);
backtrackCG.reset();
// Remove from the queue if we don't have more backtrack points for that state
if (backtrackChoices.isEmpty()) {
- cgMap.remove(stateId);
backtrackMap.remove(stateId);
backtrackStateQ.remove(stateId);
}
- return backtrackCG;
}
- private void setNextBacktrackPoint(IntChoiceFromSet icsCG) {
-
- HashSet<IntChoiceFromSet> backtrackCGs = new HashSet<>(cgMap.values());
- if (!isFirstResetDone) {
- // Reset the last CG of every LinkedList in the map and set done everything else
- for (Integer stateId : cgMap.keySet()) {
- setBacktrackCG(stateId);
+ // --- Functions related to the reachability analysis when there is a state match
+
+ // We use backtrackPointsList to analyze the reachable states/events when there is a state match:
+ // 1) Whenever there is state match, there is a cycle of events
+ // 2) We need to analyze and find conflicts for the reachable choices/events in the cycle
+ // 3) Then we create a new backtrack point for every new conflict
+ private void analyzeReachabilityAndCreateBacktrackPoints(VM vm, int stateId) {
+ // Perform this analysis only when:
+ // 1) there is a state match,
+ // 2) this is not during a switch to a new execution,
+ // 3) at least 2 choices/events have been explored (choiceCounter > 1),
+ // 4) the matched state has been encountered in the current execution, and
+ // 5) state > 0 (state 0 is for boolean CG)
+ if (!vm.isNewState() && !isEndOfExecution && choiceCounter > 1 && (stateId > 0)) {
+ if (currVisitedStates.contains(stateId)) {
+ // Update the backtrack sets in the cycle
+ updateBacktrackSetsInCycle(stateId);
+ } else if (prevVisitedStates.contains(stateId)) { // We visit a state in a previous execution
+ // Update the backtrack sets in a previous execution
+ updateBacktrackSetsInPreviousExecution(stateId);
}
-// activeBacktrackCGs.addAll(cgMap.values());
- isFirstResetDone = true;
- } else {
- // Check if we still have backtrack points for the current CG
- int currStateId = icsCG.getStateId();
- if (backtrackMap.containsKey(currStateId)) {
- setBacktrackCG(currStateId);
- } else {
-// activeBacktrackCGs.remove(icsCG);
- // We try to reset new CGs (if we do have) when we are running out of active CGs
- if (!backtrackStateQ.isEmpty()) {
- // Reset the next CG with the latest state
- int hiStateId = backtrackStateQ.peek();
- IntChoiceFromSet backtrackCG = setBacktrackCG(hiStateId);
-// activeBacktrackCGs.add(backtrackCG);
- }
+ }
+ }
+
+ // Get the start event for the past execution trace when there is a state matched from a past execution
+ private int getPastConflictChoice(int stateId, ArrayList<BacktrackPoint> pastBacktrackPointList) {
+ // Iterate and find the first occurrence of the state ID
+ // It is guaranteed that a choice should be found because the state ID is in the list
+ int pastConfChoice = 0;
+ for(int i = 0; i<pastBacktrackPointList.size(); i++) {
+ BacktrackPoint backtrackPoint = pastBacktrackPointList.get(i);
+ int stId = backtrackPoint.getStateId();
+ if (stId == stateId) {
+ pastConfChoice = i;
+ break;
}
}
- // Clear unused CGs
- for(IntChoiceFromSet cg : cgList) {
- if (!backtrackCGs.contains(cg)) {
- cg.setDone();
+ return pastConfChoice;
+ }
+
+ // Get a sorted list of reachable state IDs starting from the input stateId
+ private ArrayList<Integer> getReachableStateIds(Set<Integer> stateIds, int stateId) {
+ // Only include state IDs equal or greater than the input stateId: these are reachable states
+ ArrayList<Integer> sortedStateIds = new ArrayList<>();
+ for(Integer stId : stateIds) {
+ if (stId >= stateId) {
+ sortedStateIds.add(stId);
}
}
- cgList.clear();
- }
-
- // --- Functions related to the visible operation dependency graph implementation discussed in the SPIN paper
-
- // This method checks whether a choice is reachable in the VOD graph from a reference choice (BFS algorithm)
- //private boolean isReachableInVODGraph(int checkedChoice, int referenceChoice) {
- private boolean isReachableInVODGraph(int currentChoice) {
- // Extract previous and current events
- int choiceIndex = currentChoice % refChoices.length;
- int currEvent = refChoices[choiceIndex];
- int prevEvent = refChoices[choiceIndex - 1];
- // Record visited choices as we search in the graph
- HashSet<Integer> visitedChoice = new HashSet<>();
- visitedChoice.add(prevEvent);
- 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(prevEvent)) {
- nodesToVisit.addAll(vodGraphMap.get(prevEvent));
- while(!nodesToVisit.isEmpty()) {
- int choice = nodesToVisit.getFirst();
- if (choice == currEvent) {
- return true;
- }
- if (visitedChoice.contains(choice)) { // If there is a loop then we don't find it
- return false;
- }
- // Continue searching
- visitedChoice.add(choice);
- HashSet<Integer> choiceNextNodes = vodGraphMap.get(choice);
- if (choiceNextNodes != null) {
- // Add only if there is a mapping for next nodes
- for (Integer nextNode : choiceNextNodes) {
- // Skip cycles
- if (nextNode == choice) {
- continue;
- }
- nodesToVisit.addLast(nextNode);
- }
+ Collections.sort(sortedStateIds);
+ return sortedStateIds;
+ }
+
+ // Update the backtrack sets in the cycle
+ private void updateBacktrackSetsInCycle(int stateId) {
+ // Find the choice/event that marks the start of this cycle: first choice we explore for conflicts
+ int conflictChoice = stateToChoiceCounterMap.get(stateId);
+ int currentChoice = choiceCounter - 1;
+ // Find conflicts between choices/events in this cycle (we scan forward in the cycle, not backward)
+ while (conflictChoice < currentChoice) {
+ for (int eventCounter = conflictChoice + 1; eventCounter <= currentChoice; eventCounter++) {
+ if (isConflictFound(eventCounter, conflictChoice, false) && isNewConflict(conflictChoice, eventCounter)) {
+ createBacktrackingPoint(conflictChoice, eventCounter, false);
}
}
+ conflictChoice++;
}
- return false;
}
- private void updateVODGraph(int currChoiceValue) {
- // Update the graph when we have the current choice value
+ // TODO: OPTIMIZATION!
+ // Check and make sure that state ID and choice haven't been explored for this trace
+ private boolean isNotChecked(HashMap<Integer, HashSet<Integer>> checkedStateIdAndChoice,
+ BacktrackPoint backtrackPoint) {
+ int stateId = backtrackPoint.getStateId();
+ int choice = backtrackPoint.getChoice();
HashSet<Integer> choiceSet;
- if (vodGraphMap.containsKey(prevChoiceValue)) {
- // If the key already exists, just retrieve it
- choiceSet = vodGraphMap.get(prevChoiceValue);
+ if (checkedStateIdAndChoice.containsKey(stateId)) {
+ choiceSet = checkedStateIdAndChoice.get(stateId);
+ if (choiceSet.contains(choice)) {
+ // State ID and choice found. It has been checked!
+ return false;
+ }
} else {
- // Create a new entry
choiceSet = new HashSet<>();
- vodGraphMap.put(prevChoiceValue, choiceSet);
+ checkedStateIdAndChoice.put(stateId, choiceSet);
+ }
+ choiceSet.add(choice);
+
+ return true;
+ }
+
+ // Update the backtrack sets in a previous execution
+ private void updateBacktrackSetsInPreviousExecution(int stateId) {
+ // Don't check a past trace twice!
+ HashSet<ReachableTrace> checkedTrace = new HashSet<>();
+ // Don't check the same event twice for a revisited state
+ HashMap<Integer, HashSet<Integer>> checkedStateIdAndChoice = new HashMap<>();
+ // Get sorted reachable state IDs
+ ArrayList<Integer> reachableStateIds = getReachableStateIds(rGraph.keySet(), stateId);
+ // Iterate from this state ID until the biggest state ID
+ for(Integer stId : reachableStateIds) {
+ // Find the right reachability graph object that contains the stateId
+ ArrayList<ReachableTrace> rTraces = rGraph.get(stId);
+ for (ReachableTrace rTrace : rTraces) {
+ if (!checkedTrace.contains(rTrace)) {
+ // Find the choice/event that marks the start of the subtrace from the previous execution
+ ArrayList<BacktrackPoint> pastBacktrackPointList = rTrace.getPastBacktrackPointList();
+ HashMap<Integer, ReadWriteSet> pastReadWriteFieldsMap = rTrace.getPastReadWriteFieldsMap();
+ int pastConfChoice = getPastConflictChoice(stId, pastBacktrackPointList);
+ int conflictChoice = choiceCounter;
+ // Iterate from the starting point until the end of the past execution trace
+ while (pastConfChoice < pastBacktrackPointList.size() - 1) { // BacktrackPoint list always has a surplus of 1
+ // Get the info of the event from the past execution trace
+ BacktrackPoint confBtrackPoint = pastBacktrackPointList.get(pastConfChoice);
+ if (isNotChecked(checkedStateIdAndChoice, confBtrackPoint)) {
+ ReadWriteSet rwSet = pastReadWriteFieldsMap.get(pastConfChoice);
+ // Append this event to the current list and map
+ backtrackPointList.add(confBtrackPoint);
+ readWriteFieldsMap.put(choiceCounter, rwSet);
+ for (int eventCounter = conflictChoice - 1; eventCounter >= 0; eventCounter--) {
+ if (isConflictFound(eventCounter, conflictChoice, true) && isNewConflict(conflictChoice, eventCounter)) {
+ createBacktrackingPoint(conflictChoice, eventCounter, true);
+ }
+ }
+ // Remove this event to replace it with a new one
+ backtrackPointList.remove(backtrackPointList.size() - 1);
+ readWriteFieldsMap.remove(choiceCounter);
+ }
+ pastConfChoice++;
+ }
+ checkedTrace.add(rTrace);
+ }
+ }
}
- choiceSet.add(currChoiceValue);
- prevChoiceValue = currChoiceValue;
}
}
projects / jpf-core.git / blobdiff