//
// 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.heuristic;
import gov.nasa.jpf.Config;
import gov.nasa.jpf.vm.VM;
/**
* heuristic state prioritizer that tries to minimize re-scheduling
*/
public class GlobalSwitchThread extends SimplePriorityHeuristic {
private int[] threads;
public GlobalSwitchThread (Config config, VM vm) {
super(config, vm);
int threadHistorySize = config.getInt("search.heuristic.thread_history_size", 10);
threads = new int[threadHistorySize];
for (int i = 0; i < threads.length; i++) {
threads[i] = -1;
}
}
protected int computeHeuristicValue () {
int aliveThreads = vm.getThreadList().getMatchingCount(aliveThread);
int lastRun = vm.getLastTransition().getThreadIndex();
int h_value = 0;
if (aliveThreads > 1) {
for (int i = 0; i < threads.length; i++) {
if (lastRun == threads[i]) {
h_value += ((threads.length - i) * aliveThreads);
}
}
}
int temp0 = threads[0];
int temp1;
threads[0] = lastRun;
for (int i = 1; i < threads.length; i++) {
temp1 = threads[i];
threads[i] = temp0;
temp0 = temp1;
}
return h_value;
}
}