Initial import

[jpf-core.git] / src / main / gov / nasa / jpf / search / heuristic / GlobalSwitchThread.java

diff --git a/src/main/gov/nasa/jpf/search/heuristic/GlobalSwitchThread.java b/src/main/gov/nasa/jpf/search/heuristic/GlobalSwitchThread.java
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+/*
+ * Copyright (C) 2014, United States Government, as represented by the
+ * Administrator of the National Aeronautics and Space Administration.
+ * All rights reserved.
+ *
+ * The Java Pathfinder core (jpf-core) platform is 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.
+ */
+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;
+    }
+  }
+
+  @Override
+  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;
+  }
+}