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
/**
- * 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.
+ * This a DPOR implementation for event-driven applications with loops that create cycles of state matching
+ * In this new DPOR 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 lastCGStateId; // Record the state of the currently active CG
private int maxEventChoice;
// Data structure to track the events seen by each state to track cycles (containing all events) for termination
private HashSet<Integer> currVisitedStates; // States being visited in the current execution
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<String> doneBacktrackSet; // Record state ID and trace that are done
- 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<BacktrackExecution>> backtrackMap; // Track created backtracking points
+ private PriorityQueue<Integer> backtrackStateQ; // Heap that returns the latest state
+ private Execution currentExecution; // Holds the information about the current execution
+ private HashSet<String> doneBacktrackSet; // Record state ID and trace already constructed
+ 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, HashSet<TransitionEvent>> rGraph; // Reachability graph for past executions
// 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;
}
+ String outputFile = config.getString("file_output");
+ if (!outputFile.isEmpty()) {
+ try {
+ fileWriter = new PrintWriter(new FileWriter(outputFile, true), true);
+ } catch (IOException e) {
+ }
+ }
isBooleanCGFlipped = false;
+ numOfConflicts = 0;
+ numOfTransitions = 0;
+ restorableStateMap = new HashMap<>();
initializeStatesVariables();
}
" which is " + detail + " Transition: " + transition + "\n");
}
if (stateReductionMode) {
+ // Only add a transition into R-Graph when it advances the state
+ addTransitionToRGRaph();
updateStateInfo(search);
}
}
}
}
+ 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 (!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();
}
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);
+ fairSchedulingAndTransition(icsCG, vm);
+ // Update backtrack set of an executed event (transition): one transition before this one
+ updateBacktrackSet(currentExecution, choiceCounter - 1);
+ // 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++;
}
}
// Handle the read/write accesses that occur through iterators
analyzeReadWriteAccesses(executedInsn, ti, currentChoice);
}
- // Analyze conflicts from next instructions
- if (nextInsn instanceof JVMFieldInstruction) {
- // Skip the constructor because it is called once and does not have shared access with other objects
- if (!nextInsn.getMethodInfo().getName().equals("<init>")) {
- String fieldClass = ((JVMFieldInstruction) nextInsn).getFieldInfo().getFullName();
- if (!isFieldExcluded(fieldClass)) {
- // Check for conflict (go backward from current choice and get the first conflict)
- for (int eventCounter = currentChoice - 1; eventCounter >= 0; eventCounter--) {
- // Check for conflicts with Write fields for both Read and Write instructions
- // 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);
- }
- }
- }
- }
- }
- }
}
}
}
// -- INNER CLASSES
+ // This class compactly stores backtrack execution:
+ // 1) backtrack choice list, and
+ // 2) first backtrack point (linking with predecessor execution)
+ private class BacktrackExecution {
+ private Integer[] choiceList;
+ private TransitionEvent firstTransition;
+
+ public BacktrackExecution(Integer[] choList, TransitionEvent fTransition) {
+ choiceList = choList;
+ firstTransition = fTransition;
+ }
+
+ public Integer[] getChoiceList() {
+ return choiceList;
+ }
+
+ public TransitionEvent getFirstTransition() {
+ return firstTransition;
+ }
+ }
+
+ // This class stores a representation of the execution graph node
+ // TODO: We can modify this class to implement some optimization (e.g., clock-vector)
+ // TODO: We basically need to keep track of:
+ // TODO: (1) last read/write access to each memory location
+ // TODO: (2) last state with two or more incoming events (transitions)
+ private class Execution {
+ private HashMap<IntChoiceFromSet, Integer> cgToChoiceMap; // Map between CG to choice numbers for O(1) access
+ private ArrayList<TransitionEvent> executionTrace; // The BacktrackPoint objects of this execution
+ private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
+ private HashMap<Integer, TransitionEvent> stateToTransitionMap; // For O(1) access to backtrack point
+
+ public Execution() {
+ cgToChoiceMap = new HashMap<>();
+ executionTrace = new ArrayList<>();
+ readWriteFieldsMap = new HashMap<>();
+ stateToTransitionMap = new HashMap<>();
+ }
+
+ public void addTransition(TransitionEvent newBacktrackPoint) {
+ executionTrace.add(newBacktrackPoint);
+ }
+
+ public void clearCGToChoiceMap() {
+ cgToChoiceMap = null;
+ }
+
+ public TransitionEvent getTransitionFromState(int stateId) {
+ if (stateToTransitionMap.containsKey(stateId)) {
+ return stateToTransitionMap.get(stateId);
+ }
+ return null;
+ }
+
+ public int getChoiceFromCG(IntChoiceFromSet icsCG) {
+ return cgToChoiceMap.get(icsCG);
+ }
+
+ public ArrayList<TransitionEvent> getExecutionTrace() {
+ return executionTrace;
+ }
+
+ public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
+ return readWriteFieldsMap;
+ }
+
+ public TransitionEvent getFirstTransition() {
+ return executionTrace.get(0);
+ }
+
+ public TransitionEvent getLastTransition() {
+ return executionTrace.get(executionTrace.size() - 1);
+ }
+
+ public boolean isNew() {
+ return executionTrace.size() == 1;
+ }
+
+ public void mapCGToChoice(IntChoiceFromSet icsCG, int choice) {
+ cgToChoiceMap.put(icsCG, choice);
+ }
+
+ public void mapStateToTransition(int stateId, TransitionEvent backtrackPoint) {
+ stateToTransitionMap.put(stateId, backtrackPoint);
+ }
+ }
+
+ // This class compactly stores a predecessor
+ // 1) a predecessor execution
+ // 2) the predecessor choice in that predecessor execution
+ private class Predecessor {
+ private int predecessorChoice; // Predecessor choice
+ private Execution predecessorExecution; // Predecessor execution
+
+ public Predecessor(int predChoice, Execution predExec) {
+ predecessorChoice = predChoice;
+ predecessorExecution = predExec;
+ }
+
+ public int getPredecessorChoice() {
+ return predecessorChoice;
+ }
+
+ public Execution getPredecessorExecution() {
+ return predecessorExecution;
+ }
+ }
+
+ // This class compactly stores backtrack points:
+ // 1) CG,
+ // 2) state ID,
+ // 3) choice,
+ // 4) predecessors (for backward DFS).
+ private class TransitionEvent {
+ private IntChoiceFromSet transitionCG; // CG at this transition
+ private int stateId; // State at this transition
+ private int choice; // Choice chosen at this transition
+ private Execution execution; // The execution where this transition belongs
+ private int choiceCounter; // Choice counter at this transition
+ private HashSet<Predecessor> predecessors; // Maps incoming events/transitions (execution and choice)
+
+ public TransitionEvent() {
+ transitionCG = null;
+ stateId = -1;
+ choice = -1;
+ execution = null;
+ choiceCounter = -1;
+ predecessors = new HashSet<>();
+ }
+
+ public void setTransitionCG(IntChoiceFromSet cg) {
+ transitionCG = cg;
+ }
+
+ public void setStateId(int stId) {
+ stateId = stId;
+ }
+
+ public void setChoice(int cho) {
+ choice = cho;
+ }
+
+ public void setChoiceCounter(int choCounter) {
+ choiceCounter = choCounter;
+ }
+
+ public IntChoiceFromSet getTransitionCG() { return transitionCG; }
+
+ public int getStateId() {
+ return stateId;
+ }
+
+ public int getChoice() {
+ return choice;
+ }
+
+ public int getChoiceCounter() {
+ return choiceCounter;
+ }
+
+ public void setExecution(Execution exec) {
+ execution = exec;
+ }
+
+ public Execution getExecution() {
+ return execution;
+ }
+
+ public HashSet<Predecessor> getPredecessors() {
+ return predecessors;
+ }
+
+ public void recordPredecessor(Execution execution, int choice) {
+ predecessors.add(new Predecessor(choice, execution));
+ }
+ }
+
// This class compactly stores Read and Write field sets
// 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> readMap;
+ private HashMap<String, Integer> writeMap;
public ReadWriteSet() {
- readSet = new HashMap<>();
- writeSet = new HashMap<>();
+ readMap = new HashMap<>();
+ writeMap = new HashMap<>();
}
public void addReadField(String field, int objectId) {
- readSet.put(field, objectId);
+ readMap.put(field, objectId);
}
public void addWriteField(String field, int objectId) {
- writeSet.put(field, objectId);
+ writeMap.put(field, objectId);
+ }
+
+ public void removeReadField(String field) {
+ readMap.remove(field);
+ }
+
+ public void removeWriteField(String field) {
+ writeMap.remove(field);
+ }
+
+ public boolean isEmpty() {
+ return readMap.isEmpty() && writeMap.isEmpty();
+ }
+
+ public ReadWriteSet getCopy() {
+ ReadWriteSet copyRWSet = new ReadWriteSet();
+ // Copy the maps in the set into the new object copy
+ copyRWSet.setReadMap(new HashMap<>(this.getReadMap()));
+ copyRWSet.setWriteMap(new HashMap<>(this.getWriteMap()));
+ return copyRWSet;
+ }
+
+ public Set<String> getReadSet() {
+ return readMap.keySet();
+ }
+
+ public Set<String> getWriteSet() {
+ return writeMap.keySet();
}
public boolean readFieldExists(String field) {
- return readSet.containsKey(field);
+ return readMap.containsKey(field);
}
public boolean writeFieldExists(String field) {
- return writeSet.containsKey(field);
+ return writeMap.containsKey(field);
}
public int readFieldObjectId(String field) {
- return readSet.get(field);
+ return readMap.get(field);
}
public int writeFieldObjectId(String field) {
- return writeSet.get(field);
+ return writeMap.get(field);
}
- }
- // This class compactly stores backtracking points: 1) backtracking ChoiceGenerator, 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 HashMap<String, Integer> getReadMap() {
+ return readMap;
+ }
- public BacktrackPoint(IntChoiceFromSet cg, Integer[] choices) {
- backtrackCG = cg;
- backtrackChoices = choices;
+ private HashMap<String, Integer> getWriteMap() {
+ return writeMap;
}
- public IntChoiceFromSet getBacktrackCG() {
- return backtrackCG;
+ private void setReadMap(HashMap<String, Integer> rMap) {
+ readMap = rMap;
}
- public Integer[] getBacktrackChoices() {
- return backtrackChoices;
+ private void setWriteMap(HashMap<String, Integer> wMap) {
+ writeMap = wMap;
}
}
private final static String JAVA_STRING_LIB = "java.lang.String";
// -- FUNCTIONS
- private void checkAndEnforceFairScheduling(IntChoiceFromSet icsCG) {
+ private void fairSchedulingAndTransition(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);
}
}
+ // Get state ID and associate it with this transition
+ int stateId = vm.getStateId();
+ // Get a new transition
+ TransitionEvent transition;
+ if (currentExecution.isNew()) {
+ // We need to handle the first transition differently because this has a predecessor execution
+ transition = currentExecution.getFirstTransition();
+ } else {
+ transition = new TransitionEvent();
+ transition.recordPredecessor(currentExecution, choiceCounter - 1);
+ }
+ transition.setExecution(currentExecution);
+ transition.setTransitionCG(icsCG);
+ transition.setStateId(stateId);
+ transition.setChoice(refChoices[choiceIndex]);
+ transition.setChoiceCounter(choiceCounter);
+ // Add new transition to the current execution
+ currentExecution.mapStateToTransition(stateId, transition);
+ currentExecution.addTransition(transition);
+ currentExecution.mapCGToChoice(icsCG, choiceCounter);
+ // 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 copyOfChoices;
}
- // --- Functions related to cycle detection
+ // --- Functions related to cycle detection and reachability graph
// Detect cycles in the current execution/trace
// We terminate the execution iff:
// (2) the state has one or more cycles that involve all the events
// With simple approach we only need to check for a re-visited state.
// Basically, we have to check that we have executed all events between two occurrences of such state.
- private boolean containsCyclesWithAllEvents(int stId) {
+ private boolean completeFullCycle(int stId) {
// False if the state ID hasn't been recorded
if (!stateToEventMap.containsKey(stId)) {
choices = null;
refChoices = null;
choiceCounter = 0;
- lastCGStateId = 0;
maxEventChoice = 0;
// Cycle tracking
currVisitedStates = new HashSet<>();
// Backtracking
backtrackMap = new HashMap<>();
backtrackStateQ = new PriorityQueue<>(Collections.reverseOrder());
- cgList = new ArrayList<>();
- cgMap = new HashMap<>();
- conflictPairMap = new HashMap<>();
+ currentExecution = new Execution();
+ currentExecution.addTransition(new TransitionEvent()); // Always start with 1 backtrack point
doneBacktrackSet = new HashSet<>();
- readWriteFieldsMap = new HashMap<>();
- // VOD graph
- prevChoiceValue = -1;
- vodGraphMap = new HashMap<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ rGraph = new HashMap<>();
// Booleans
isEndOfExecution = false;
- isFirstResetDone = false;
}
private void mapStateToEvent(int nextChoiceValue) {
}
}
+ // Save the current transition into R-Graph
+ // Basically the current transition is reachable from the final state of the previous transition in this execution
+ private void addTransitionToRGRaph() {
+ // Get the current transition
+ TransitionEvent currTrans = currentExecution.getLastTransition();
+ // This transition is reachable from this source state when it has advanced the state
+ int stateId = currTrans.getStateId();
+ // Add transition into R-Graph
+ HashSet<TransitionEvent> transitionSet;
+ if (rGraph.containsKey(stateId)) {
+ transitionSet = rGraph.get(stateId);
+ } else {
+ transitionSet = new HashSet<>();
+ }
+ // Insert into the set if it does not contain it yet
+ if (!transitionSet.contains(currTrans)) {
+ transitionSet.add(currTrans);
+ }
+ }
+
private boolean terminateCurrentExecution() {
// We need to check all the states that have just been visited
// Often a transition (choice/event) can result into forwarding/backtracking to a number of states
for(Integer stateId : justVisitedStates) {
- if (prevVisitedStates.contains(stateId) || containsCyclesWithAllEvents(stateId)) {
+ if (prevVisitedStates.contains(stateId) || completeFullCycle(stateId)) {
return true;
}
}
// 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);
}
+ analyzeReachabilityAndCreateBacktrackPoints(search.getVM(), stateId);
+ stateToChoiceCounterMap.put(stateId, choiceCounter);
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, Execution parentExecution, int parentChoice) {
// Insert backtrack point to the right state ID
- LinkedList<Integer[]> backtrackList;
+ LinkedList<BacktrackExecution> backtrackExecList;
if (backtrackMap.containsKey(stateId)) {
- backtrackList = backtrackMap.get(stateId);
+ backtrackExecList = 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);
+ backtrackExecList = new LinkedList<>();
+ backtrackMap.put(stateId, backtrackExecList);
}
+ // Add the new backtrack execution object
+ TransitionEvent backtrackTransition = new TransitionEvent();
+ backtrackTransition.recordPredecessor(parentExecution, parentChoice);
+ backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, backtrackTransition));
// Add to priority queue
if (!backtrackStateQ.contains(stateId)) {
backtrackStateQ.add(stateId);
private int checkAndAdjustChoice(int currentChoice, VM vm) {
// 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);
- if (currChoiceInd != currChoiceFromCG) {
- currentChoice = (currentChoice - currChoiceInd) + currChoiceFromCG;
+ 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();
+ }
+ // Find the choice related to the IntIntervalGenerator CG from the map
+ currentChoice = currentExecution.getChoiceFromCG((IntChoiceFromSet) parentCG);
}
return currentChoice;
}
- private void createBacktrackingPoint(int currentChoice, int confEvtNum) {
+ private void createBacktrackingPoint(Execution execution, int currentChoice, int conflictChoice) {
// 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];
+ //int firstChoice = choices[actualChoice];
+ ArrayList<TransitionEvent> pastTrace = execution.getExecutionTrace();
+ ArrayList<TransitionEvent> currTrace = currentExecution.getExecutionTrace();
+ int currChoice = currTrace.get(currentChoice).getChoice();
+ int stateId = pastTrace.get(conflictChoice).getStateId();
+ // Check if this trace has been done from this state
+ if (isTraceAlreadyConstructed(currChoice, stateId)) {
+ return;
+ }
// Put the conflicting event numbers first and reverse the order
- int actualCurrCho = currentChoice % refChoices.length;
- int actualConfEvtNum = confEvtNum % refChoices.length;
- // We use the actual choices here in case they have been modified/adjusted
- newChoiceList[0] = choices[actualCurrCho];
- newChoiceList[1] = choices[actualConfEvtNum];
+ newChoiceList[0] = currChoice;
// 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]) {
+ for (int i = 0, j = 1; i < refChoices.length; i++) {
+ if (refChoices[i] != newChoiceList[0]) {
newChoiceList[j] = refChoices[i];
j++;
}
}
- // Record the backtracking point in the stack as well
- IntChoiceFromSet backtrackCG = cgList.get(confEvtNum);
- // Check if this trace has been done starting from this state
- if (isTraceConstructed(newChoiceList, backtrackCG)) {
- return;
- }
- //BacktrackPoint backtrackPoint = new BacktrackPoint(backtrackCG, newChoiceList);
- addNewBacktrackPoint(backtrackCG, newChoiceList);
+ // Parent choice is conflict choice - 1
+ addNewBacktrackPoint(stateId, newChoiceList, execution, conflictChoice - 1);
}
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) {
- // Check if we are reaching the end of our execution: no more backtracking points to explore
- if (!backtrackMap.isEmpty()) {
- setNextBacktrackPoint(icsCG);
+ 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 (TransitionEvent backtrackTransition : currentExecution.getExecutionTrace()) {
+ backtrackTransition.getTransitionCG().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);
+ // This marks a transitional period to the new CG
+ isEndOfExecution = true;
+ }
+
+ private boolean isConflictFound(Execution execution, int reachableChoice, int conflictChoice,
+ ReadWriteSet currRWSet) {
+
+ ArrayList<TransitionEvent> executionTrace = execution.getExecutionTrace();
+ HashMap<Integer, ReadWriteSet> execRWFieldsMap = execution.getReadWriteFieldsMap();
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!execRWFieldsMap.containsKey(conflictChoice) ||
+ executionTrace.get(reachableChoice).getChoice() == executionTrace.get(conflictChoice).getChoice()) {
+ return false;
+ }
+ // R/W set of choice/event that may have a potential conflict
+ ReadWriteSet evtRWSet = execRWFieldsMap.get(conflictChoice);
+ // 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) {
+ // Remove this from the read set as we are tracking per memory location
+ evtRWSet.removeWriteField(writeField);
+ return true;
+ } else if (evtRWSet.writeFieldExists(writeField) && evtRWSet.writeFieldObjectId(writeField) == currObjId) {
+ // Remove this from the write set as we are tracking per memory location
+ evtRWSet.removeReadField(writeField);
+ 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) {
+ // Remove this from the write set as we are tracking per memory location
+ evtRWSet.removeWriteField(readField);
+ return true;
}
- // 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;
}
+ // Return false if no conflict is found
+ return false;
}
- 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 boolean isConflictFound(Execution execution, int reachableChoice, int conflictChoice) {
+
+ ArrayList<TransitionEvent> executionTrace = execution.getExecutionTrace();
+ HashMap<Integer, ReadWriteSet> execRWFieldsMap = execution.getReadWriteFieldsMap();
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!execRWFieldsMap.containsKey(conflictChoice) ||
+ executionTrace.get(reachableChoice).getChoice() == executionTrace.get(conflictChoice).getChoice()) {
+ return false;
+ }
+ // Current R/W set
+ ReadWriteSet currRWSet = execRWFieldsMap.get(reachableChoice);
+ // R/W set of choice/event that may have a potential conflict
+ ReadWriteSet evtRWSet = execRWFieldsMap.get(conflictChoice);
+ // 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 ReadWriteSet getReadWriteSet(int currentChoice) {
// Do the analysis to get Read and Write accesses to fields
ReadWriteSet rwSet;
// We already have an entry
- if (readWriteFieldsMap.containsKey(currentChoice)) {
- rwSet = readWriteFieldsMap.get(currentChoice);
+ HashMap<Integer, ReadWriteSet> currReadWriteFieldsMap = currentExecution.getReadWriteFieldsMap();
+ if (currReadWriteFieldsMap.containsKey(currentChoice)) {
+ rwSet = currReadWriteFieldsMap.get(currentChoice);
} else { // We need to create a new entry
rwSet = new ReadWriteSet();
- readWriteFieldsMap.put(currentChoice, rwSet);
+ currReadWriteFieldsMap.put(currentChoice, rwSet);
}
return rwSet;
}
- 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) || choices[actualCurrCho] == choices[actualEvtCntr]) {
- return false;
- }
- ReadWriteSet rwSet = readWriteFieldsMap.get(eventCounter);
- int currObjId = ((JVMFieldInstruction) nextInsn).getFieldInfo().getClassInfo().getClassObjectRef();
- // Check for conflicts with Write fields for both Read and Write instructions
- if (((nextInsn instanceof WriteInstruction || nextInsn instanceof ReadInstruction) &&
- rwSet.writeFieldExists(fieldClass) && rwSet.writeFieldObjectId(fieldClass) == currObjId) ||
- (nextInsn instanceof WriteInstruction && rwSet.readFieldExists(fieldClass) &&
- rwSet.readFieldObjectId(fieldClass) == currObjId)) {
- return true;
- }
- return false;
- }
-
private boolean isFieldExcluded(String field) {
// Check against "starts-with", "ends-with", and "contains" list
if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, field) ||
return false;
}
- private boolean isNewConflict(int currentEvent, int eventNumber) {
- HashSet<Integer> conflictSet;
- if (!conflictPairMap.containsKey(currentEvent)) {
- conflictSet = new HashSet<>();
- conflictPairMap.put(currentEvent, conflictSet);
- } else {
- conflictSet = conflictPairMap.get(currentEvent);
- }
- // If this conflict has been recorded before, we return false because
- // we don't want to save this backtrack point twice
- if (conflictSet.contains(eventNumber)) {
- return false;
- }
- // If it hasn't been recorded, then do otherwise
- conflictSet.add(eventNumber);
- return true;
- }
-
- private boolean isTraceConstructed(Integer[] choiceList, IntChoiceFromSet backtrackCG) {
- // Concatenate state ID and trace in a string, e.g., "1:10234"
- int stateId = backtrackCG.getStateId();
+ // Check if this trace is already constructed
+ private boolean isTraceAlreadyConstructed(int firstChoice, 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(':');
- for(Integer choice : choiceList) {
- sb.append(choice);
- }
+ sb.append(firstChoice);
// Check if the trace has been constructed as a backtrack point for this state
if (doneBacktrackSet.contains(sb.toString())) {
return true;
return false;
}
- private void resetStatesForNewExecution(IntChoiceFromSet icsCG) {
+ // Reset data structure for each new execution
+ private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
if (choices == null || choices != icsCG.getAllChoices()) {
// Reset state variables
choiceCounter = 0;
choices = icsCG.getAllChoices();
refChoices = copyChoices(choices);
- lastCGStateId = icsCG.getStateId();
- // Clearing data structures
- conflictPairMap.clear();
- readWriteFieldsMap.clear();
- stateToEventMap.clear();
+ // Clear data structures
+ currVisitedStates = new HashSet<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ stateToEventMap = new HashMap<>();
isEndOfExecution = false;
- // Adding this CG as the first CG for this execution
- cgList.add(icsCG);
}
}
- private void setBacktrackCG(int stateId) {
+ // Set a backtrack point for a particular state
+ 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
+ LinkedList<BacktrackExecution> backtrackExecutions = backtrackMap.get(stateId);
+ BacktrackExecution backtrackExecution = backtrackExecutions.removeLast();
+ backtrackCG.setNewValues(backtrackExecution.getChoiceList()); // Get the last from the queue
+ backtrackCG.setStateId(stateId);
backtrackCG.reset();
+ // Update current execution with this new execution
+ Execution newExecution = new Execution();
+ TransitionEvent firstTransition = backtrackExecution.getFirstTransition();
+ newExecution.addTransition(firstTransition);
+ // Try to free some memory since this map is only used for the current execution
+ currentExecution.clearCGToChoiceMap();
+ currentExecution = newExecution;
// Remove from the queue if we don't have more backtrack points for that state
- if (backtrackChoices.isEmpty()) {
- cgMap.remove(stateId);
+ if (backtrackExecutions.isEmpty()) {
backtrackMap.remove(stateId);
backtrackStateQ.remove(stateId);
}
}
- private void setNextBacktrackPoint(IntChoiceFromSet icsCG) {
+ // Update backtrack sets
+ // 1) recursively, and
+ // 2) track accesses per memory location (per shared variable/field)
+ private void updateBacktrackSet(Execution execution, int currentChoice) {
+ // Choice/event we want to check for conflict against (start from actual choice)
+ int conflictChoice = currentChoice;
+ // Copy ReadWriteSet object
+ HashMap<Integer, ReadWriteSet> currRWFieldsMap = execution.getReadWriteFieldsMap();
+ ReadWriteSet currRWSet = currRWFieldsMap.get(currentChoice).getCopy();
+ // Memorize visited TransitionEvent object while performing backward DFS to avoid getting caught up in a cycle
+ HashSet<TransitionEvent> visited = new HashSet<>();
+ // Update backtrack set recursively
+ updateBacktrackSetRecursive(execution, currentChoice, conflictChoice, currRWSet, visited);
+ }
- 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);
- }
- isFirstResetDone = true;
- } else {
- // Check if we still have backtrack points for the last state after the last backtrack
- if (backtrackMap.containsKey(lastCGStateId)) {
- setBacktrackCG(lastCGStateId);
- } else {
- // 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();
- setBacktrackCG(hiStateId);
- }
- }
+ private void updateBacktrackSetRecursive(Execution execution, int currentChoice, int conflictChoice,
+ ReadWriteSet currRWSet, HashSet<TransitionEvent> visited) {
+ // Halt when we have found the first read/write conflicts for all memory locations
+ if (currRWSet.isEmpty()) {
+ return;
}
- // Clear unused CGs
- for(IntChoiceFromSet cg : cgList) {
- if (!backtrackCGs.contains(cg)) {
- cg.setDone();
+ TransitionEvent confTrans = execution.getExecutionTrace().get(conflictChoice);
+ // Halt when we have visited this transition (in a cycle)
+ if (visited.contains(confTrans)) {
+ return;
+ }
+ visited.add(confTrans);
+ // Explore all predecessors
+ for (Predecessor predecessor : confTrans.getPredecessors()) {
+ // Get the predecessor (previous conflict choice)
+ conflictChoice = predecessor.getPredecessorChoice();
+ execution = predecessor.getPredecessorExecution();
+ // Check if a conflict is found
+ if (isConflictFound(execution, currentChoice, conflictChoice, currRWSet)) {
+ createBacktrackingPoint(execution, currentChoice, conflictChoice);
}
+ // Continue performing DFS if conflict is not found
+ updateBacktrackSetRecursive(execution, currentChoice, conflictChoice, currRWSet, visited);
}
- 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);
- }
+ }
+
+ // --- Functions related to the reachability analysis when there is a state match
+
+ 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) state > 0 (state 0 is for boolean CG)
+ if (!vm.isNewState() && !isEndOfExecution && choiceCounter > 1 && (stateId > 0)) {
+ if (currVisitedStates.contains(stateId)) {
+ // Get the backtrack point from the current execution
+ TransitionEvent transition = currentExecution.getTransitionFromState(stateId);
+ transition.recordPredecessor(currentExecution, choiceCounter - 1);
+ updateBacktrackSetsFromPreviousExecution(stateId);
+ } else if (prevVisitedStates.contains(stateId)) { // We visit a state in a previous execution
+ // Update past executions with a predecessor
+ HashSet<TransitionEvent> reachableTransitions = rGraph.get(stateId);
+ for(TransitionEvent transition : reachableTransitions) {
+ Execution execution = transition.getExecution();
+ transition.recordPredecessor(execution, choiceCounter - 1);
}
+ updateBacktrackSetsFromPreviousExecution(stateId);
}
}
- return false;
}
- private void updateVODGraph(int currChoiceValue) {
- // Update the graph when we have the current choice value
- HashSet<Integer> choiceSet;
- if (vodGraphMap.containsKey(prevChoiceValue)) {
- // If the key already exists, just retrieve it
- choiceSet = vodGraphMap.get(prevChoiceValue);
- } else {
- // Create a new entry
- choiceSet = new HashSet<>();
- vodGraphMap.put(prevChoiceValue, choiceSet);
+ // Update the backtrack sets from previous executions
+ private void updateBacktrackSetsFromPreviousExecution(int stateId) {
+ // Collect all the reachable transitions from R-Graph
+ HashSet<TransitionEvent> reachableTransitions = rGraph.get(stateId);
+ for(TransitionEvent transition : reachableTransitions) {
+ Execution execution = transition.getExecution();
+ int currentChoice = transition.getChoiceCounter();
+ updateBacktrackSet(execution, currentChoice);
}
- choiceSet.add(currChoiceValue);
- prevChoiceValue = currChoiceValue;
}
}
projects / jpf-core.git / blobdiff