Java tutorial
/* * CPAchecker is a tool for configurable software verification. * This file is part of CPAchecker. * * Copyright (C) 2007-2014 Dirk Beyer * All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * * CPAchecker web page: * http://cpachecker.sosy-lab.org */ package org.sosy_lab.cpachecker.cpa.arg; import static com.google.common.base.Preconditions.checkNotNull; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.Set; import java.util.SortedSet; import java.util.TreeSet; import java.util.logging.Level; import org.sosy_lab.cpachecker.core.interfaces.AbstractState; import org.sosy_lab.cpachecker.core.interfaces.Precision; import org.sosy_lab.cpachecker.core.reachedset.ReachedSet; import org.sosy_lab.cpachecker.core.reachedset.UnmodifiableReachedSet; import org.sosy_lab.cpachecker.core.reachedset.UnmodifiableReachedSetWrapper; import org.sosy_lab.cpachecker.exceptions.CPAException; import org.sosy_lab.cpachecker.util.Precisions; import com.google.common.base.Functions; import com.google.common.base.Preconditions; import com.google.common.base.Predicate; import com.google.common.base.Predicates; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableSet; import com.google.common.collect.Maps; import com.google.common.collect.SetMultimap; /** * This class is a modifiable live view of a reached set, which shows the ARG * relations between the elements, and enforces a correct ARG when the set is * modified through this wrapper. */ public class ARGReachedSet { private final int refinementNumber; private final ARGCPA cpa; private final ReachedSet mReached; private final UnmodifiableReachedSet mUnmodifiableReached; /** * Constructor for ARGReachedSet as a simple wrapper around ReachedSet. * If possible, do not use this constructor but the other one that takes * an ARGCPA instance as parameter. * This class notifies the ARGCPA of removed counterexamples if possible * to reduce memory usage. */ public ARGReachedSet(ReachedSet pReached) { this(pReached, null); } public ARGReachedSet(ReachedSet pReached, ARGCPA pCpa) { this(pReached, pCpa, -1); } /** * This constructor may be used only during an refinement * which should be added to the refinement graph .dot file. */ ARGReachedSet(ReachedSet pReached, ARGCPA pCpa, int pRefinementNumber) { mReached = checkNotNull(pReached); mUnmodifiableReached = new UnmodifiableReachedSetWrapper(mReached); cpa = pCpa; refinementNumber = pRefinementNumber; } public UnmodifiableReachedSet asReachedSet() { return mUnmodifiableReached; } /** * Remove an element and all elements below it from the tree. Re-add all those * elements to the waitlist which have children which are either removed or were * covered by removed elements. * * @param e The root of the removed subtree, may not be the initial element. */ public void removeSubtree(ARGState e) { Set<ARGState> toWaitlist = removeSubtree0(e); for (ARGState ae : toWaitlist) { mReached.reAddToWaitlist(ae); } } /** * Like {@link #removeSubtree(ARGState)}, but when re-adding elements to the * waitlist adapts precisions with respect to the supplied precision p (see * {@link #adaptPrecision(ARGState, Precision)}). * @param e The root of the removed subtree, may not be the initial element. * @param p The new precision. */ public void removeSubtree(ARGState e, Precision p, Predicate<? super Precision> pPrecisionType) { for (ARGState ae : removeSubtree0(e)) { mReached.updatePrecision(ae, adaptPrecision(mReached.getPrecision(ae), p, pPrecisionType)); mReached.reAddToWaitlist(ae); } } /** * Like {@link #removeSubtree(ARGState)}, but when re-adding elements to the * waitlist adapts precisions with respect to the supplied precision p (see * {@link #adaptPrecision(ARGState, Precision)}). * If multiple precisions are given, * adapt all matching sub-precisions of a WrappedPrecision. * * @param e The root of the removed subtree, may not be the initial element. * @param p The new precision. */ public void removeSubtree(ARGState e, List<Precision> precisions, List<Predicate<? super Precision>> precisionTypes) { Preconditions.checkArgument(precisions.size() == precisionTypes.size()); Set<ARGState> toWaitlist = removeSubtree0(e); for (ARGState ae : toWaitlist) { Precision prec = mReached.getPrecision(ae); for (int i = 0; i < precisions.size(); i++) { prec = adaptPrecision(prec, precisions.get(i), precisionTypes.get(i)); } mReached.updatePrecision(ae, prec); mReached.reAddToWaitlist(ae); } } /** * Safely remove a port of the ARG which has been proved as completely * unreachable. This method takes care of the coverage relationships of the * removed nodes, re-adding covered nodes to the waitlist if necessary. * @param rootOfInfeasiblePart The root of the subtree to remove. * @param pReached The reached set. */ public void removeInfeasiblePartofARG(ARGState rootOfInfeasiblePart) { Set<ARGState> infeasibleSubtree = rootOfInfeasiblePart.getSubgraph(); for (ARGState removedNode : infeasibleSubtree) { removeCoverageOf(removedNode); } Set<ARGState> parentsOfRoot = ImmutableSet.copyOf(rootOfInfeasiblePart.getParents()); Set<ARGState> parentsOfRemovedStates = removeSet(infeasibleSubtree); assert parentsOfRoot.equals(parentsOfRemovedStates); } /** * This method cuts of the subtree in the ARG, starting with the given state. * * Other than {@link #removeSubtree(ARGState)} and its variants, this method * does not care about keeping the coverage-relation consistent, so using this * method might, and very likely will, introduce unsoundness that has to be * handled appropriately by other means (e.g., a later full re-exploration). * * @param argState the state to be removed including its subtree */ public void cutOffSubtree(ARGState argState) { mReached.removeAll(argState.getSubgraph()); } /** * This method (re)adds the given state to the waitlist and changes the * precision of the state to the supplied precision. * * @param state the state to (re)add to the waitlist * @param the new precision to apply at this state * @param pPrecisionType the type of the precision */ public void readdToWaitlist(ARGState state, Precision precision, Predicate<? super Precision> pPrecisionType) { mReached.updatePrecision(state, adaptPrecision(mReached.getPrecision(state), precision, pPrecisionType)); mReached.reAddToWaitlist(state); } /** * Set a new precision for each single state in the reached set. * @param p The new precision, may be for a single CPA (c.f. {@link #adaptPrecision(ARGState, Precision)}). */ public void updatePrecisionGlobally(Precision pNewPrecision, Predicate<? super Precision> pPrecisionType) { Map<Precision, Precision> precisionUpdateCache = Maps.newIdentityHashMap(); for (AbstractState s : mReached) { Precision oldPrecision = mReached.getPrecision(s); Precision newPrecision = precisionUpdateCache.get(oldPrecision); if (newPrecision == null) { newPrecision = adaptPrecision(oldPrecision, pNewPrecision, pPrecisionType); precisionUpdateCache.put(oldPrecision, newPrecision); } mReached.updatePrecision(s, newPrecision); } } /** * Adapts a precision with a new precision. * If the old precision is a wrapper precision, pNewPrecision replaces the * component of the wrapper precision that corresponds to pNewPrecision. * Otherwise, pNewPrecision is returned. * @param pOldPrecision The old precision. * @param pNewPrecision New precision. * @return The adapted precision. */ private Precision adaptPrecision(Precision pOldPrecision, Precision pNewPrecision, Predicate<? super Precision> pPrecisionType) { return Precisions.replaceByType(pOldPrecision, pNewPrecision, pPrecisionType); } private Set<ARGState> removeSubtree0(ARGState e) { Preconditions.checkNotNull(e); Preconditions.checkArgument(!e.getParents().isEmpty(), "May not remove the initial element from the ARG/reached set"); dumpSubgraph(e); Set<ARGState> toUnreach = e.getSubgraph(); // collect all elements covered by the subtree List<ARGState> newToUnreach = new ArrayList<>(); for (ARGState ae : toUnreach) { newToUnreach.addAll(ae.getCoveredByThis()); } toUnreach.addAll(newToUnreach); Set<ARGState> toWaitlist = removeSet(toUnreach); return toWaitlist; } private void dumpSubgraph(ARGState e) { if (cpa == null) { return; } ARGToDotWriter refinementGraph = cpa.getRefinementGraphWriter(); if (refinementGraph == null) { return; } SetMultimap<ARGState, ARGState> successors = ARGUtils.projectARG(e, ARGUtils.CHILDREN_OF_STATE, ARGUtils.RELEVANT_STATE); SetMultimap<ARGState, ARGState> predecessors = ARGUtils.projectARG(e, ARGUtils.PARENTS_OF_STATE, ARGUtils.RELEVANT_STATE); try { refinementGraph.enterSubgraph("cluster_" + refinementNumber, "Refinement " + refinementNumber); refinementGraph.writeSubgraph(e, Functions.forMap(successors.asMap(), ImmutableSet.<ARGState>of()), Predicates.alwaysTrue(), Predicates.alwaysFalse()); refinementGraph.leaveSubgraph(); for (ARGState predecessor : predecessors.get(e)) { // insert edge from predecessor to e in global graph refinementGraph.writeEdge(predecessor, e); } } catch (IOException ex) { cpa.getLogger().logUserException(Level.WARNING, ex, "Could not write refinement graph to file"); } } /** * Remove a set of elements from the ARG and reached set. There are no sanity checks. * * The result will be a set of elements that need to be added to the waitlist * to re-discover the removed elements. These are the parents of the removed * elements which are not removed themselves. The set is sorted based on the * relation defined by {@link ARGState#compareTo(ARGState)}), i.e., oldest-first. * * @param elements the elements to remove * @return the elements to re-add to the waitlist */ private SortedSet<ARGState> removeSet(Set<ARGState> elements) { if (cpa != null) { // This method call is "just" for avoiding a memory leak, // so we can ignore it if we have no reference to the CPA, // however, users of this class should really try to provide the CPA // instance to reduce memory usage. cpa.clearCounterexamples(elements); } mReached.removeAll(elements); SortedSet<ARGState> toWaitlist = new TreeSet<>(); for (ARGState ae : elements) { for (ARGState parent : ae.getParents()) { if (!elements.contains(parent)) { toWaitlist.add(parent); } } ae.removeFromARG(); } return toWaitlist; } /** * Remove all covering relations from a node so that this node does not cover * any other node anymore. * Also adds any now uncovered leaf nodes to the waitlist. * * Call this method when you have changed (strengthened) an abstract state. */ public void removeCoverageOf(ARGState v) { for (ARGState coveredByChildOfV : ImmutableList.copyOf(v.getCoveredByThis())) { uncover(coveredByChildOfV); } assert v.getCoveredByThis().isEmpty(); } /** * Mark a covered element as non-covered. * This method also re-adds all leaves in that part of the ARG to the waitlist. * * @param element The covered ARGState to uncover. */ private void uncover(ARGState element) { element.uncover(); // this is the subtree of elements which now become uncovered Set<ARGState> uncoveredSubTree = element.getSubgraph(); for (ARGState e : uncoveredSubTree) { assert !e.isCovered(); e.setHasCoveredParent(false); if (!e.wasExpanded()) { // its a leaf mReached.reAddToWaitlist(e); } } } /** * Try covering an ARG state by other states in the reached set. * If successful, also mark the subtree below this state as covered, * which means that all states in this subtree do not cover any states anymore. * @param v The state which should be covered if possible. * @return whether the covering was successful * @throws CPAException */ public boolean tryToCover(ARGState v) throws CPAException, InterruptedException { assert v.mayCover(); cpa.getStopOperator().stop(v, mReached.getReached(v), mReached.getPrecision(v)); // ignore return value of stop, because it will always be false if (v.isCovered()) { Set<ARGState> subtree = v.getSubgraph(); subtree.remove(v); removeCoverageOf(v); for (ARGState childOfV : subtree) { // all states in the subtree (including v) may not cover anymore removeCoverageOf(childOfV); } for (ARGState childOfV : subtree) { // all states in the subtree (excluding v) // are removed from the waitlist, // are not covered anymore directly if (childOfV.isCovered()) { childOfV.uncover(); } } for (ARGState childOfV : subtree) { mReached.removeOnlyFromWaitlist(childOfV); childOfV.setHasCoveredParent(true); // each child of v now doesn't cover anything anymore assert childOfV.getCoveredByThis().isEmpty(); assert !childOfV.mayCover(); } mReached.removeOnlyFromWaitlist(v); return true; } return false; } /** * Try covering an ARG state by other states in the reached set. This method * deliberately allows for unsoundness, by not caring about keeping the * coverage relation in the ARG consistent. When asked to be sound, this * method delegates to {@link ARGReachedSet#tryToCover(ARGState)} * * @param v the state which should be covered if possible * @param beUnsound whether or not the be unsound * @return whether the covering was successful * @throws CPAException */ public boolean tryToCover(ARGState v, boolean beUnsound) throws CPAException, InterruptedException { assert v.mayCover(); if (beUnsound) { cpa.getStopOperator().stop(v, mReached.getReached(v), mReached.getPrecision(v)); return v.isCovered(); } return tryToCover(v); } public static class ForwardingARGReachedSet extends ARGReachedSet { protected final ARGReachedSet delegate; public ForwardingARGReachedSet(ARGReachedSet pReached) { super(pReached.mReached); delegate = pReached; } @Override public UnmodifiableReachedSet asReachedSet() { return delegate.asReachedSet(); } @Override public void removeSubtree(ARGState pE) { delegate.removeSubtree(pE); } @Override public void removeSubtree(ARGState pE, Precision pP, Predicate<? super Precision> pPrecisionType) { delegate.removeSubtree(pE, pP, pPrecisionType); } } }