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/*******************************************************************************
* Copyright (c) 2010-2016, Andras Szabolcs Nagy, Zoltan Ujhelyi and Daniel Varro
* Copyright (c) 2023 The Refinery Authors <https://refinery.tools/>
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.store.dse.strategy;
import tools.refinery.store.map.Version;
import tools.refinery.store.dse.DesignSpaceExplorationAdapter;
import tools.refinery.store.dse.Strategy;
import tools.refinery.store.dse.internal.Activation;
import tools.refinery.store.dse.objectives.Fitness;
import tools.refinery.store.dse.objectives.ObjectiveComparatorHelper;
import java.util.*;
public class BestFirstStrategy implements Strategy {
private DesignSpaceExplorationAdapter dseAdapter;
private int maxDepth = Integer.MAX_VALUE;
private int maxSolutions = Integer.MAX_VALUE;
private boolean backTrackIfSolution = true;
private boolean onlyBetterFirst = false;
private PriorityQueue<TrajectoryWithFitness> trajectoriesToExplore;
private record TrajectoryWithFitness(List<Version> trajectory, Fitness fitness) {
@Override
public String toString() {
return trajectory.toString() + fitness.toString();
}
@Override
public int hashCode() {
return trajectory.get(trajectory.size() - 1).hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj instanceof TrajectoryWithFitness other) {
return Objects.equals(trajectory.get(trajectory.size() - 1), other.trajectory.get(other.trajectory.size() - 1));
// return trajectory.equals(((TrajectoryWithFitness) obj).trajectory);
}
return false;
}
}
public BestFirstStrategy withDepthLimit(int maxDepth) {
if (maxDepth >= 0) {
this.maxDepth = maxDepth;
}
return this;
}
public BestFirstStrategy withSolutionLimit(int maxSolutions) {
if (maxSolutions >= 0) {
this.maxSolutions = maxSolutions;
}
return this;
}
public BestFirstStrategy continueIfHardObjectivesFulfilled() {
backTrackIfSolution = false;
return this;
}
public BestFirstStrategy goOnOnlyIfFitnessIsBetter() {
onlyBetterFirst = true;
return this;
}
@Override
public void initialize(DesignSpaceExplorationAdapter designSpaceExplorationAdapter) {
this.dseAdapter = designSpaceExplorationAdapter;
final ObjectiveComparatorHelper objectiveComparatorHelper = dseAdapter.getObjectiveComparatorHelper();
trajectoriesToExplore = new PriorityQueue<>(11,
(o1, o2) -> objectiveComparatorHelper.compare(o2.fitness, o1.fitness));
}
@Override
public void explore() {
if (maxSolutions == 0) {
return;
}
final ObjectiveComparatorHelper objectiveComparatorHelper = dseAdapter.getObjectiveComparatorHelper();
boolean globalConstraintsAreSatisfied = dseAdapter.checkGlobalConstraints();
if (!globalConstraintsAreSatisfied) {
// Global constraint is not satisfied in the first state. Terminate.
return;
}
final Fitness firstFitness = dseAdapter.getFitness();
if (firstFitness.isSatisfiesHardObjectives()) {
dseAdapter.newSolution();
// First state is a solution. Terminate.
if (backTrackIfSolution) {
return;
}
}
if (maxDepth == 0) {
return;
}
var firstTrajectoryWithFitness = new TrajectoryWithFitness(dseAdapter.getTrajectory(), firstFitness);
trajectoriesToExplore.add(firstTrajectoryWithFitness);
TrajectoryWithFitness currentTrajectoryWithFitness = null;
mainLoop: while (true) {
if (currentTrajectoryWithFitness == null) {
if (trajectoriesToExplore.isEmpty()) {
// State space is fully traversed.
return;
} else {
currentTrajectoryWithFitness = trajectoriesToExplore.element();
// New trajectory is chosen: " + currentTrajectoryWithFitness
dseAdapter.restoreTrajectory(currentTrajectoryWithFitness.trajectory);
}
}
Collection<Activation> activations = dseAdapter.getUntraversedActivations();
Iterator<Activation> iterator = activations.iterator();
while (iterator.hasNext()) {
final Activation nextActivation = iterator.next();
if (!iterator.hasNext()) {
// Last untraversed activation of the state.
trajectoriesToExplore.remove(currentTrajectoryWithFitness);
}
// Executing new activation
dseAdapter.fireActivation(nextActivation);
if (dseAdapter.isCurrentStateAlreadyTraversed()) {
// The new state is already visited.
dseAdapter.backtrack();
} else if (!dseAdapter.checkGlobalConstraints()) {
// Global constraint is not satisfied.
dseAdapter.backtrack();
} else {
final Fitness nextFitness = dseAdapter.getFitness();
if (nextFitness.isSatisfiesHardObjectives()) {
dseAdapter.newSolution();
var solutions = dseAdapter.getSolutions().size();
if (solutions >= maxSolutions) {
return;
}
// Found a solution.
if (backTrackIfSolution) {
dseAdapter.backtrack();
continue;
}
}
if (dseAdapter.getDepth() >= maxDepth) {
// Reached max depth.
dseAdapter.backtrack();
continue;
}
TrajectoryWithFitness nextTrajectoryWithFitness = new TrajectoryWithFitness(
dseAdapter.getTrajectory(), nextFitness);
trajectoriesToExplore.add(nextTrajectoryWithFitness);
int compare = objectiveComparatorHelper.compare(currentTrajectoryWithFitness.fitness,
nextTrajectoryWithFitness.fitness);
if (compare < 0) {
// Better fitness, moving on
currentTrajectoryWithFitness = nextTrajectoryWithFitness;
continue mainLoop;
} else if (compare == 0) {
if (onlyBetterFirst) {
// Equally good fitness, backtrack
dseAdapter.backtrack();
} else {
// Equally good fitness, moving on
currentTrajectoryWithFitness = nextTrajectoryWithFitness;
continue mainLoop;
}
} else {
//"Worse fitness
currentTrajectoryWithFitness = null;
continue mainLoop;
}
}
}
// State is fully traversed.
currentTrajectoryWithFitness = null;
}
// Interrupted.
}
}
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