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;
private Transition transition;
// 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;
- // Record CGs for backtracking points
- private List<IntChoiceFromSet> cgList;
// Data structure to track the events seen by each state to track cycles (containing all events) for termination
- private HashMap<Integer, HashSet<Integer>> stateToEventMap;
+ private HashSet<Integer> currVisitedStates; // States being visited in the current execution
private HashSet<Integer> justVisitedStates; // States just visited in the previous choice/event
private HashSet<Integer> prevVisitedStates; // States visited in the previous execution
- private HashSet<Integer> currVisitedStates; // States being visited in the current execution
- // Data structure to analyze field Read/Write accesses
- private HashMap<Integer, ReadWriteSet> readWriteFieldsMap;
- private HashMap<Integer, HashSet<Integer>> conflictPairMap;
+ private HashMap<Integer, HashSet<Integer>> stateToEventMap;
+ // Data structure to analyze field Read/Write accesses and conflicts
+ 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, ArrayList<ReachableTrace>> rGraph; // Create a reachability graph
+ private HashMap<Integer, ArrayList<Execution>> rGraph; // Create a reachability graph for past executions
// Boolean states
private boolean isBooleanCGFlipped;
+ 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;
- cgList = new ArrayList<>();
- stateToEventMap = new HashMap<>();
- justVisitedStates = new HashSet<>();
- prevVisitedStates = new HashSet<>();
- currVisitedStates = new HashSet<>();
- readWriteFieldsMap = new HashMap<>();
- conflictPairMap = 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;
+ 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();
}
}
// Initialize with necessary information from the CG
if (nextCG instanceof IntChoiceFromSet) {
IntChoiceFromSet icsCG = (IntChoiceFromSet) nextCG;
- // Check if CG has been initialized, otherwise initialize it
- Integer[] cgChoices = icsCG.getAllChoices();
- // Record the events (from choices)
- if (choices == null) {
- choices = cgChoices;
- // Make a copy of choices as reference
- refChoices = copyChoices(choices);
- // Record the max event choice (the last element of the choice array)
- maxEventChoice = choices[choices.length - 1];
+ if (!isEndOfExecution) {
+ // Check if CG has been initialized, otherwise initialize it
+ Integer[] cgChoices = icsCG.getAllChoices();
+ // Record the events (from choices)
+ if (choices == null) {
+ choices = cgChoices;
+ // Make a copy of choices as reference
+ refChoices = copyChoices(choices);
+ // Record the max event choice (the last element of the choice array)
+ maxEventChoice = choices[choices.length - 1];
+ }
+ icsCG.setNewValues(choices);
+ icsCG.reset();
+ // Use a modulo since choiceCounter is going to keep increasing
+ int choiceIndex = choiceCounter % choices.length;
+ icsCG.advance(choices[choiceIndex]);
+ } else {
+ // Set done all CGs while transitioning to a new execution
+ icsCG.setDone();
}
- // 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);
}
}
}
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, 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());
- // Check if we have seen this state or this state contains cycles that involve all events
- if (terminateCurrentExecution()) {
- exploreNextBacktrackSets(icsCG);
- }
justVisitedStates.clear();
choiceCounter++;
}
+ } else {
+ numOfTransitions++;
}
}
@Override
public void instructionExecuted(VM vm, ThreadInfo ti, Instruction nextInsn, Instruction executedInsn) {
if (stateReductionMode) {
- // Has to be initialized and a integer CG
- ChoiceGenerator<?> cg = vm.getChoiceGenerator();
- if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
- int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
- //if (getCurrentChoice(vm) < 0) { // If choice is -1 then skip
- if (currentChoice < 0) { // If choice is -1 then skip
- return;
- }
- // Record accesses from executed instructions
- if (executedInsn instanceof JVMFieldInstruction) {
- // Analyze only after being initialized
- String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
- // We don't care about libraries
- if (!isFieldExcluded(fieldClass)) {
- analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
+ if (!isEndOfExecution) {
+ // Has to be initialized and a integer CG
+ ChoiceGenerator<?> cg = vm.getChoiceGenerator();
+ if (cg instanceof IntChoiceFromSet || cg instanceof IntIntervalGenerator) {
+ int currentChoice = choiceCounter - 1; // Accumulative choice w.r.t the current trace
+ if (currentChoice < 0) { // If choice is -1 then skip
+ return;
}
- } else if (executedInsn instanceof INVOKEINTERFACE) {
- // 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();
+ currentChoice = checkAndAdjustChoice(currentChoice, vm);
+ // Record accesses from executed instructions
+ if (executedInsn instanceof JVMFieldInstruction) {
+ // Analyze only after being initialized
+ String fieldClass = ((JVMFieldInstruction) executedInsn).getFieldInfo().getFullName();
+ // We don't care about libraries
if (!isFieldExcluded(fieldClass)) {
- // Check for conflict (go backward from current choice and get the first conflict)
- for (int evtCntr = currentChoice - 1; evtCntr >= 0; evtCntr--) {
- if (!readWriteFieldsMap.containsKey(evtCntr)) { // Skip if this event does not have any Read/Write set
- continue;
- }
- ReadWriteSet rwSet = readWriteFieldsMap.get(evtCntr);
- 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)) {
- // Check and record a backtrack set for just once!
- if (successfullyRecordConflictPair(currentChoice, evtCntr)) {
- // Lines 4-8 of the algorithm in the paper page 11 (see the heading note above)
-// if (vm.isNewState() || isReachableInVODGraph(refChoices[currentChoice], refChoices[currentChoice-1])) {
-// createBacktrackChoiceList(currentChoice, eventNumber);
-// }
- }
- }
+ analyzeReadWriteAccesses(executedInsn, fieldClass, currentChoice);
+ }
+ } else if (executedInsn instanceof INVOKEINTERFACE) {
+ // 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)) {
+ findFirstConflictAndCreateBacktrackPoint(currentChoice, nextInsn, fieldClass);
}
}
}
// == HELPERS
- // -- INNER CLASS
+
+ // -- INNER CLASSES
+
+ // This class compactly stores backtrack execution:
+ // 1) backtrack choice list, and
+ // 2) backtrack execution
+ private class BacktrackExecution {
+ private Integer[] choiceList;
+ private Execution execution;
+
+ public BacktrackExecution(Integer[] choList, Execution exec) {
+ choiceList = choList;
+ execution = exec;
+ }
+
+ public Integer[] getChoiceList() {
+ return choiceList;
+ }
+
+ public Execution getExecution() {
+ return execution;
+ }
+ }
+
+ // This class compactly stores backtrack points:
+ // 1) backtrack state ID, and
+ // 2) backtracking choices
+ private class BacktrackPoint {
+ 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, int stId, int cho) {
+ backtrackCG = cg;
+ stateId = stId;
+ choice = cho;
+ }
+
+ public IntChoiceFromSet getBacktrackCG() { return backtrackCG; }
+
+ public int getStateId() {
+ return stateId;
+ }
+
+ public int getChoice() {
+ return choice;
+ }
+ }
+
+ // This class stores a representation of the execution graph node
+ private class Execution {
+ private ArrayList<BacktrackPoint> executionTrace; // The BacktrackPoint objects of this execution
+ private int parentChoice; // The parent's choice that leads to this execution
+ private Execution parent; // Store the parent for backward DFS to find conflicts
+ private HashMap<Integer, ReadWriteSet> readWriteFieldsMap; // Record fields that are accessed
+
+ public Execution() {
+ executionTrace = new ArrayList<>();
+ parentChoice = -1;
+ parent = null;
+ readWriteFieldsMap = new HashMap<>();
+ }
+
+ public void addBacktrackPoint(BacktrackPoint newBacktrackPoint) {
+ executionTrace.add(newBacktrackPoint);
+ }
+
+ public ArrayList<BacktrackPoint> getExecutionTrace() {
+ return executionTrace;
+ }
+
+ public int getParentChoice() {
+ return parentChoice;
+ }
+
+ public Execution getParent() {
+ return parent;
+ }
+
+ public HashMap<Integer, ReadWriteSet> getReadWriteFieldsMap() {
+ return readWriteFieldsMap;
+ }
+
+ public void setParentChoice(int parChoice) {
+ parentChoice = parChoice;
+ }
+
+ public void setParent(Execution par) {
+ parent = par;
+ }
+ }
+
// 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
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 stores a compact representation of a reachability graph for past executions
+// private class ReachableTrace {
+// private ArrayList<BacktrackPoint> pastBacktrackPointList;
+// private HashMap<Integer, ReadWriteSet> pastReadWriteFieldsMap;
+//
+// public ReachableTrace(ArrayList<BacktrackPoint> btrackPointList,
+// HashMap<Integer, ReadWriteSet> rwFieldsMap) {
+// pastBacktrackPointList = btrackPointList;
+// pastReadWriteFieldsMap = rwFieldsMap;
+// }
+//
+// public ArrayList<BacktrackPoint> getPastBacktrackPointList() {
+// return pastBacktrackPointList;
+// }
+//
+// public HashMap<Integer, ReadWriteSet> getPastReadWriteFieldsMap() {
+// return pastReadWriteFieldsMap;
+// }
+// }
+
// -- CONSTANTS
private final static String DO_CALL_METHOD = "doCall";
// We exclude fields that come from libraries (Java and Groovy), and also the infrastructure
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();
+ currentExecution.addBacktrackPoint(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 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:
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());
+ currentExecution = new Execution();
+ doneBacktrackSet = new HashSet<>();
+ 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
}
}
+ private void saveExecutionToRGraph(int stateId) {
+ // Save execution state into the reachability graph 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) {
+ ArrayList<Execution> reachableExecutions;
+ if (!prevVisitedStates.contains(stateId)) {
+ reachableExecutions = new ArrayList<>();
+ rGraph.put(stateId, reachableExecutions);
+ } else {
+ reachableExecutions = rGraph.get(stateId);
+ }
+ reachableExecutions.add(currentExecution);
+ }
+ }
+
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
// 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);
}
+ saveExecutionToRGraph(stateId);
+ 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(int stateId, Integer[] newChoiceList, Execution parentExecution, int parentChoice) {
+ // Insert backtrack point to the right state ID
+ LinkedList<BacktrackExecution> backtrackExecList;
+ if (backtrackMap.containsKey(stateId)) {
+ backtrackExecList = backtrackMap.get(stateId);
+ } else {
+ backtrackExecList = new LinkedList<>();
+ backtrackMap.put(stateId, backtrackExecList);
+ }
+ // Add the new backtrack execution object
+ Execution newExecution = new Execution();
+ newExecution.setParent(parentExecution);
+ newExecution.setParentChoice(parentChoice);
+ backtrackExecList.addFirst(new BacktrackExecution(newChoiceList, newExecution));
+ // Add to priority queue
+ if (!backtrackStateQ.contains(stateId)) {
+ backtrackStateQ.add(stateId);
+ }
+ }
+
// Analyze Read/Write accesses that are directly invoked on fields
private void analyzeReadWriteAccesses(Instruction executedInsn, String fieldClass, int currentChoice) {
// Do the analysis to get Read and Write accesses to fields
}
// Get the iterated object whose property is accessed
ElementInfo eiAccessObj = VM.getVM().getHeap().get(frameSlots[1]);
+ if (eiAccessObj == null) {
+ return;
+ }
// We exclude library classes (they start with java, org, etc.) and some more
String objClassName = eiAccessObj.getClassInfo().getName();
if (excludeThisForItStartsWith(EXCLUDED_FIELDS_STARTS_WITH_LIST, objClassName) ||
}
}
+ 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 = 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 backtrackChoice, int conflictChoice, Execution execution) {
+
+ // 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<BacktrackPoint> pastTrace = execution.getExecutionTrace();
+ ArrayList<BacktrackPoint> currTrace = currentExecution.getExecutionTrace();
+ int btrackChoice = currTrace.get(backtrackChoice).getChoice();
+ int stateId = pastTrace.get(conflictChoice).getStateId();
+ // Check if this trace has been done from this state
+ if (isTraceAlreadyConstructed(btrackChoice, stateId)) {
+ return;
+ }
+ // Put the conflicting event numbers first and reverse the order
+ newChoiceList[0] = btrackChoice;
+ newChoiceList[1] = pastTrace.get(conflictChoice).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]) {
+ newChoiceList[j] = refChoices[i];
+ j++;
+ }
+ }
+ // Parent choice is conflict choice - 1
+ addNewBacktrackPoint(stateId, newChoiceList, execution, conflictChoice - 1);
+ }
+
private boolean excludeThisForItContains(String[] excludedStrings, String className) {
for (String excludedField : excludedStrings) {
if (className.contains(excludedField)) {
return false;
}
- private void exploreNextBacktrackSets(IntChoiceFromSet icsCG) {
- // Save all the visited states when starting a new execution of trace
- prevVisitedStates.addAll(currVisitedStates);
- currVisitedStates.clear();
+ 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 : currentExecution.getExecutionTrace()) {
+ 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);
+ // 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 findFirstConflictAndCreateBacktrackPoint(int currentChoice, Instruction nextInsn, String fieldClass) {
+ // Check for conflict (go backward from current choice and get the first conflict)
+ Execution execution = currentExecution;
+ // Actual choice of the current execution trace
+ //int actualChoice = currentChoice % refChoices.length;
+ // Choice/event we want to check for conflict against (start from actual choice)
+ int pastChoice = currentChoice;
+ // Perform backward DFS through the execution graph
+ while (true) {
+ // Get the next conflict choice
+ if (pastChoice > 0) {
+ // Case #1: check against a previous choice in the same execution for conflict
+ pastChoice = pastChoice - 1;
+ } else { // pastChoice == 0 means we are at the first BacktrackPoint of this execution path
+ // Case #2: check against a previous choice in a parent execution
+ int parentChoice = execution.getParentChoice();
+ if (parentChoice > -1) {
+ // Get the parent execution
+ execution = execution.getParent();
+ pastChoice = execution.getParentChoice();
+ } else {
+ // If parent is -1 then this is the first execution (it has no parent) and we stop here
+ break;
+ }
+ }
+ // Check if a conflict is found
+ if (isConflictFound(nextInsn, fieldClass, currentChoice, pastChoice, execution)) {
+ createBacktrackingPoint(currentChoice, pastChoice, execution);
+ break; // Stop at the first found conflict
+ }
+ }
+ }
+
+ private boolean isConflictFound(Instruction nextInsn, String fieldClass, int currentChoice,
+ int pastChoice, Execution pastExecution) {
+
+ HashMap<Integer, ReadWriteSet> pastRWFieldsMap = pastExecution.getReadWriteFieldsMap();
+ ArrayList<BacktrackPoint> pastTrace = pastExecution.getExecutionTrace();
+ ArrayList<BacktrackPoint> currTrace = currentExecution.getExecutionTrace();
+ // Skip if this event does not have any Read/Write set or the two events are basically the same event (number)
+ if (!pastRWFieldsMap.containsKey(pastChoice) ||
+ //choices[actualChoice] == pastTrace.get(pastChoice).getChoice()) {
+ currTrace.get(currentChoice).getChoice() == pastTrace.get(pastChoice).getChoice()) {
+ return false;
+ }
+ HashMap<Integer, ReadWriteSet> currRWFieldsMap = pastExecution.getReadWriteFieldsMap();
+ ReadWriteSet rwSet = currRWFieldsMap.get(pastChoice);
+ 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 isConflictFound(int reachableChoice, int conflictChoice, Execution execution) {
+
+ ArrayList<BacktrackPoint> 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;
}
return false;
}
- private boolean successfullyRecordConflictPair(int currentEvent, int eventNumber) {
- HashSet<Integer> conflictSet;
- if (!conflictPairMap.containsKey(currentEvent)) {
- conflictSet = new HashSet<>();
- conflictPairMap.put(currentEvent, conflictSet);
- } else {
- conflictSet = conflictPairMap.get(currentEvent);
+ 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(':');
+ sb.append(firstChoice);
+ // Check if the trace has been constructed as a backtrack point for this state
+ if (doneBacktrackSet.contains(sb.toString())) {
+ return true;
}
- // If this conflict has been recorded before, we return false because
- // we don't want to service this backtrack point twice
- if (conflictSet.contains(eventNumber)) {
- return false;
+ doneBacktrackSet.add(sb.toString());
+ return false;
+ }
+
+ private void resetStatesForNewExecution(IntChoiceFromSet icsCG, VM vm) {
+ if (choices == null || choices != icsCG.getAllChoices()) {
+ // Reset state variables
+ choiceCounter = 0;
+ choices = icsCG.getAllChoices();
+ refChoices = copyChoices(choices);
+ // Clear data structures
+ currVisitedStates = new HashSet<>();
+ stateToChoiceCounterMap = new HashMap<>();
+ stateToEventMap = new HashMap<>();
+ isEndOfExecution = false;
+ }
+ }
+
+ private void setBacktrackCG(int stateId, IntChoiceFromSet backtrackCG) {
+ // Set a backtrack CG based on a state ID
+ 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 = backtrackExecution.getExecution();
+ if (newExecution.getParentChoice() == -1) {
+ // If it is -1 then that means we should start from the end of the parent trace for backward DFS
+ ArrayList<BacktrackPoint> parentTrace = newExecution.getParent().getExecutionTrace();
+ newExecution.setParentChoice(parentTrace.size() - 1);
+ }
+ currentExecution = newExecution;
+ // Remove from the queue if we don't have more backtrack points for that state
+ if (backtrackExecutions.isEmpty()) {
+ backtrackMap.remove(stateId);
+ backtrackStateQ.remove(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);
+ }*/
}
- // If it hasn't been recorded, then do otherwise
- conflictSet.add(eventNumber);
+ }
+
+ // 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;
+ }
+ }
+ 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);
+ }
+ }
+ 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 reachableChoice = stateToChoiceCounterMap.get(stateId);
+ int cycleEndChoice = choiceCounter - 1;
+ // Find conflicts between choices/events in this cycle (we scan forward in the cycle, not backward)
+ while (reachableChoice < cycleEndChoice) {
+ for (int conflictChoice = reachableChoice + 1; conflictChoice <= cycleEndChoice; conflictChoice++) {
+ if (isConflictFound(reachableChoice, conflictChoice, currentExecution)) {
+ createBacktrackingPoint(reachableChoice, conflictChoice, currentExecution);
+ }
+ }
+ reachableChoice++;
+ }
+ }
+
+ // 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 (checkedStateIdAndChoice.containsKey(stateId)) {
+ choiceSet = checkedStateIdAndChoice.get(stateId);
+ if (choiceSet.contains(choice)) {
+ // State ID and choice found. It has been checked!
+ return false;
+ }
+ } else {
+ choiceSet = new HashSet<>();
+ 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<Execution> 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<Execution> rExecutions = rGraph.get(stId);
+ for (Execution rExecution : rExecutions) {
+ if (!checkedTrace.contains(rExecution)) {
+ // Find the choice/event that marks the start of the subtrace from the previous execution
+ ArrayList<BacktrackPoint> pastExecutionTrace = rExecution.getExecutionTrace();
+ HashMap<Integer, ReadWriteSet> pastReadWriteFieldsMap = rExecution.getReadWriteFieldsMap();
+ int pastConfChoice = getPastConflictChoice(stId, pastExecutionTrace);
+ int conflictChoice = choiceCounter;
+ // Iterate from the starting point until the end of the past execution trace
+ while (pastConfChoice < pastExecutionTrace.size() - 1) { // BacktrackPoint list always has a surplus of 1
+ // Get the info of the event from the past execution trace
+ BacktrackPoint confBtrackPoint = pastExecutionTrace.get(pastConfChoice);
+ if (isNotChecked(checkedStateIdAndChoice, confBtrackPoint)) {
+ ReadWriteSet rwSet = pastReadWriteFieldsMap.get(pastConfChoice);
+ // Append this event to the current list and map
+ ArrayList<BacktrackPoint> currentTrace = currentExecution.getExecutionTrace();
+ HashMap<Integer, ReadWriteSet> currRWFieldsMap = currentExecution.getReadWriteFieldsMap();
+ currentTrace.add(confBtrackPoint);
+ currRWFieldsMap.put(choiceCounter, rwSet);
+ for (int pastChoice = conflictChoice - 1; pastChoice >= 0; pastChoice--) {
+ if (isConflictFound(conflictChoice, pastChoice, rExecution)) {
+ createBacktrackingPoint(conflictChoice, pastChoice, rExecution);
+ }
+ }
+ // Remove this event to replace it with a new one
+ currentTrace.remove(currentTrace.size() - 1);
+ currRWFieldsMap.remove(choiceCounter);
+ }
+ pastConfChoice++;
+ }
+ checkedTrace.add(rExecution);
+ }
+ }
+ }
+ }
}
projects / jpf-core.git / blobdiff