//
// Copyright (C) 2006 United States Government as represented by the
// Administrator of the National Aeronautics and Space Administration
// (NASA). All Rights Reserved.
//
// This software is distributed under the NASA Open Source Agreement
// (NOSA), version 1.3. The NOSA has been approved by the Open Source
// Initiative. See the file NOSA-1.3-JPF at the top of the distribution
// directory tree for the complete NOSA document.
//
// THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
// KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
// LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
// SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
// A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
// THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
// DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
//
package gov.nasa.jpf.search;
import gov.nasa.jpf.Config;
import gov.nasa.jpf.vm.VM;
/**
* standard depth first model checking (but can be bounded by search depth
* and/or explicit Verify.ignoreIf)
*/
public class DFSearch extends Search {
public DFSearch (Config config, VM vm) {
super(config,vm);
}
public boolean requestBacktrack () {
doBacktrack = true;
return true;
}
/**
* state model of the search
* next new -> action
* T T forward
* T F backtrack, forward
* F T backtrack, forward
* F F backtrack, forward
*
* end condition
* backtrack failed (no saved states)
* | property violation (currently only checked in new states)
* | search constraint (depth or memory or time)
*
* <2do> we could split the properties into forward and backtrack properties,
* the latter ones being usable for liveness properties that are basically
* condition accumulators for sub-paths of the state space, to be checked when
* we backtrack to the state where they were introduced.
*/
public void search () {
boolean depthLimitReached = false;
depth = 0;
notifySearchStarted();
System.out.println("====================================================== DFSSearch");
while (!done) {
if (checkAndResetBacktrackRequest() || !isNewState() || isEndState() || isIgnoredState() || depthLimitReached ) {
if (!backtrack()) { // backtrack not possible, done
break;
}
depthLimitReached = false;
depth--;
notifyStateBacktracked();
}
if (forward()) {
depth++;
notifyStateAdvanced();
if (currentError != null){
notifyPropertyViolated();
if (hasPropertyTermination()) {
break;
}
// for search.multiple_errors we go on and treat this as a new state
// but hasPropertyTermination() will issue a backtrack request
}
if (depth >= depthLimit) {
depthLimitReached = true;
notifySearchConstraintHit("depth limit reached: " + depthLimit);
continue;
}
if (!checkStateSpaceLimit()) {
notifySearchConstraintHit("memory limit reached: " + minFreeMemory);
// can't go on, we exhausted our memory
break;
}
} else { // forward did not execute any instructions
notifyStateProcessed();
}
}
notifySearchFinished();
}
public boolean supportsBacktrack () {
return true;
}
}