2 * Copyright (C) 2014, United States Government, as represented by the
3 * Administrator of the National Aeronautics and Space Administration.
6 * The Java Pathfinder core (jpf-core) platform is licensed under the
7 * Apache License, Version 2.0 (the "License"); you may not use this file except
8 * in compliance with the License. You may obtain a copy of the License at
10 * http://www.apache.org/licenses/LICENSE-2.0.
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
18 package gov.nasa.jpf.search.heuristic;
20 import gov.nasa.jpf.Config;
21 import gov.nasa.jpf.vm.VM;
22 import gov.nasa.jpf.vm.Path;
26 * Heuristic to maximize thread interleavings. It is particularly good at
27 * flushing out concurrency errors, since it schedules different threads
28 * as much as possible.
31 public class Interleaving extends SimplePriorityHeuristic {
35 public Interleaving (Config config, VM vm) {
38 historyLimit = config.getInt("search.heuristic.thread_history_limit", -1);
42 * heuristic based on how often, how long ago, and within how many
43 * live threads a certain thread did run
46 protected int computeHeuristicValue () {
47 int aliveThreads = vm.getThreadList().getMatchingCount(aliveThread);
49 Path path = vm.getPath();
50 int pathSize = path.size();
52 int tid = vm.getCurrentThread().getId();
55 if (aliveThreads > 1) { // otherwise there's nothing to interleave
57 for (int i= Math.max(0, pathSize - historyLimit); i<pathSize; i++) {
58 if (path.get(i).getThreadIndex() == tid) {
59 h_value += (pathSize - i) * aliveThreads;