From 1f4068e4a688cab36250d691513cfb99dd25fdbf Mon Sep 17 00:00:00 2001 From: rtrimana Date: Fri, 10 Apr 2020 15:29:50 -0700 Subject: [PATCH] Fixing a bug: misunderstood how the VOD graph is supposed to be generated; we basically track the transitions that produce new states. --- .../nasa/jpf/listener/DPORStateReducer.java | 70 +++++++++++-------- 1 file changed, 42 insertions(+), 28 deletions(-) diff --git a/src/main/gov/nasa/jpf/listener/DPORStateReducer.java b/src/main/gov/nasa/jpf/listener/DPORStateReducer.java index 632edea..f034f09 100644 --- a/src/main/gov/nasa/jpf/listener/DPORStateReducer.java +++ b/src/main/gov/nasa/jpf/listener/DPORStateReducer.java @@ -74,10 +74,12 @@ public class DPORStateReducer extends ListenerAdapter { private ArrayList backtrackPointList; // Record backtrack points (CG, state Id, and choice) private HashMap> conflictPairMap; // Record conflicting events private HashSet doneBacktrackSet; // Record state ID and trace already constructed + private HashMap newStateEventMap; // Record event producing a new state ID private HashMap readWriteFieldsMap; // Record fields that are accessed private HashMap restorableStateMap; // Maps state IDs to the restorable state object // Visible operation dependency graph implementation (SPIN paper) related fields + private int currChoiceValue; private int prevChoiceValue; private HashMap> vodGraphMap; // Visible operation dependency graph (VOD graph) @@ -216,8 +218,6 @@ public class DPORStateReducer extends ListenerAdapter { fairSchedulingAndBacktrackPoint(icsCG, vm); // 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(vm, icsCG); @@ -265,7 +265,7 @@ public class DPORStateReducer extends ListenerAdapter { 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)) { + if (vm.isNewState() || isReachableInVODGraph(currentChoice, vm)) { createBacktrackingPoint(currentChoice, eventCounter); } } @@ -375,6 +375,8 @@ public class DPORStateReducer extends ListenerAdapter { icsCG.setChoice(currCGIndex, expectedChoice); } } + // Update current choice + currChoiceValue = refChoices[choiceIndex]; // Record state ID and choice/event as backtrack point int stateId = vm.getStateId(); backtrackPointList.add(new BacktrackPoint(icsCG, stateId, refChoices[choiceIndex])); @@ -432,8 +434,10 @@ public class DPORStateReducer extends ListenerAdapter { backtrackPointList = new ArrayList<>(); conflictPairMap = new HashMap<>(); doneBacktrackSet = new HashSet<>(); + newStateEventMap = new HashMap<>(); readWriteFieldsMap = new HashMap<>(); // VOD graph + currChoiceValue = 0; prevChoiceValue = -1; vodGraphMap = new HashMap<>(); // Booleans @@ -472,6 +476,8 @@ public class DPORStateReducer extends ListenerAdapter { stateToEventMap.put(stateId, eventSet); } justVisitedStates.add(stateId); + // Update the VOD graph when there is a new state + updateVODGraph(search.getVM()); } // --- Functions related to Read/Write access analysis on shared fields @@ -774,23 +780,26 @@ public class DPORStateReducer extends ListenerAdapter { // --- 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 + // This method checks whether a choice/event (transition) is reachable from the choice/event that produces + // the state right before this state in the VOD graph + // We use a BFS algorithm for this purpose + private boolean isReachableInVODGraph(int currentChoice, VM vm) { + // Current event int choiceIndex = currentChoice % refChoices.length; - int prevChoIndex = (currentChoice - 1) % refChoices.length; int currEvent = refChoices[choiceIndex]; - int prevEvent = refChoices[prevChoIndex]; - // Record visited choices as we search in the graph - HashSet visitedChoice = new HashSet<>(); - visitedChoice.add(prevEvent); - LinkedList 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. + // Previous event + int stateId = vm.getStateId(); // A state that has been seen + int prevEvent = newStateEventMap.get(stateId); + // Only start traversing the graph if prevEvent has an outgoing edge if (vodGraphMap.containsKey(prevEvent)) { + // Record visited choices as we search in the graph + HashSet visitedChoice = new HashSet<>(); + visitedChoice.add(prevEvent); + // Get the first nodes to visit (the neighbors of prevEvent) + LinkedList nodesToVisit = new LinkedList<>(); nodesToVisit.addAll(vodGraphMap.get(prevEvent)); - while(!nodesToVisit.isEmpty()) { + // Traverse the graph using BFS + while (!nodesToVisit.isEmpty()) { int choice = nodesToVisit.removeFirst(); if (choice == currEvent) { return true; @@ -816,18 +825,23 @@ public class DPORStateReducer extends ListenerAdapter { return false; } - private void updateVODGraph(int currChoiceValue) { - // Update the graph when we have the current choice value - HashSet 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); + private void updateVODGraph(VM vm) { + // Do this only if it is a new state + if (vm.isNewState()) { + // Update the graph when we have the current choice value + HashSet 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); + } + choiceSet.add(currChoiceValue); + prevChoiceValue = currChoiceValue; + // Map this state ID to the event (transition) that produces it + newStateEventMap.put(vm.getStateId(), currChoiceValue); } - choiceSet.add(currChoiceValue); - prevChoiceValue = currChoiceValue; } } -- 2.34.1