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Java > Open Source Codes > gov > nasa > jpf > search > heuristic > GlobalSwitchThread


1 //
2 // Copyright (C) 2005 United States Government as represented by the
3 // Administrator of the National Aeronautics and Space Administration
4 // (NASA). All Rights Reserved.
5 //
6 // This software is distributed under the NASA Open Source Agreement
7 // (NOSA), version 1.3. The NOSA has been approved by the Open Source
8 // Initiative. See the file NOSA-1.3-JPF at the top of the distribution
9 // directory tree for the complete NOSA document.
10 //
11 // THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
12 // KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
13 // LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
14 // SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
15 // A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
16 // THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
17 // DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
18 //
19 package gov.nasa.jpf.search.heuristic;
20
21 import gov.nasa.jpf.Config;
22 import gov.nasa.jpf.VM;
23 import gov.nasa.jpf.jvm.TrailInfo;
24
25
26 /**
27  * heuristic state prioritizer that tries to minimize re-scheduling
28  */
29 public class GlobalSwitchThread implements Heuristic {
30   private int[] threads;
31   VM vm;
32
33   public GlobalSwitchThread (Config config, HeuristicSearch hSearch) {
34     int threadHistorySize = config.getInt("search.heuristic.thread_history_size", 10);
35     
36     vm = hSearch.getVM();
37     threads = new int[threadHistorySize];
38
39     for (int i = 0; i < threads.length; i++) {
40       threads[i] = -1;
41     }
42   }
43
44   public int heuristicValue () {
45     int aliveThreads = vm.getAliveThreadCount();
46
47     int lastRun = ((TrailInfo) vm.getLastTransition()).getThread();
48     int h_value = 0;
49
50     if (aliveThreads > 1) {
51       for (int i = 0; i < threads.length; i++) {
52         if (lastRun == threads[i]) {
53           h_value += ((threads.length - i) * aliveThreads);
54         }
55       }
56     }
57
58     int temp0 = threads[0];
59     int temp1;
60     threads[0] = lastRun;
61
62     for (int i = 1; i < threads.length; i++) {
63       temp1 = threads[i];
64       threads[i] = temp0;
65       temp0 = temp1;
66     }
67
68     return h_value;
69   }
70
71   public void processParent () {
72   }
73 }
74
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