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+// Copyright 2008, 2009 Brady J. Garvin
+
+// This file is part of Covering Arrays by Simulated Annealing (CASA).
+
+// CASA is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// CASA is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with CASA. If not, see <http://www.gnu.org/licenses/>.
+
+
+#ifndef ANNEALING_FILTER_H
+#define ANNEALING_FILTER_H
+
+#include <cassert>
+#include <iostream>
+
+#include "search/GreedyFilter.H"
+#include "events/Listener.H"
+
+// Decides, according to the rules of simulated annealing, when to take good
+// moves and when to take bad ones.
+
+// Should be added as a listener to search iterations in order that cooling be
+// synchronized with the search.
+
+template<class STATE, class COST>class AnnealingFilter :
+ public GreedyFilter<STATE,COST>,
+ public Listener<SearchIteration> {
+
+ typedef Heuristic<STATE,COST> HeuristicT;
+ typedef Goal<STATE> GoalT;
+
+ double temperature;
+ const double decay;
+
+public:
+ AnnealingFilter(double temperature, double decay) :
+ temperature(temperature),
+ decay(decay) {
+ assert(0 <= decay);
+ assert(decay <= 1);
+ }
+ virtual ~AnnealingFilter() {}
+
+ void setTemperature(double temperature) {
+ this->temperature = temperature;
+ }
+
+ virtual double convertToDelta(COST childEstimate, COST parentEstimate) const
+ = 0;
+
+ void signal(const SearchIteration&message) {
+ temperature *= decay;
+ }
+
+ void operator()
+ (std::set<STATE>&children,
+ const STATE&parent,
+ const HeuristicT&heuristic,
+ const GoalT&goal) const {
+ GreedyFilter<STATE,COST>::operator()(children, heuristic, goal);
+ assert(children.size() <= 1);
+ if (children.size()) {
+ typename std::set<STATE>::iterator child = children.begin();
+ COST childEstimate = heuristic.estimate(*child, goal);
+ COST parentEstimate = heuristic.estimate(parent, goal);
+ if (!(parentEstimate < childEstimate)) {
+ // Always take good moves.
+ return;
+ }
+ double delta = convertToDelta(childEstimate, parentEstimate);
+ double probability = exp(delta / temperature);
+ int boundary = (int)(probability * RAND_MAX);
+ if (rand() < boundary) {
+ // Sometimes take bad moves.
+ return;
+ }
+ children.clear();
+ }
+ // When no moves are possible or a bad move is rejected, keep the parent.
+ children.insert(parent);
+ }
+};
+
+#endif