/*
* Copyright 2014 Red Hat, Inc. and/or its affiliates.
*
* 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 org.optaplanner.core.impl.exhaustivesearch.node.comparator;
import java.io.Serializable;
import java.util.Comparator;
import org.optaplanner.core.impl.exhaustivesearch.node.ExhaustiveSearchNode;
/**
* Investigate the nodes with a better optimistic bound first, then deeper nodes.
*/
public class OptimisticBoundFirstNodeComparator implements Comparator<ExhaustiveSearchNode>, Serializable {
public OptimisticBoundFirstNodeComparator(boolean scoreBounderEnabled) {
if (!scoreBounderEnabled) {
throw new IllegalArgumentException("This " + getClass().getSimpleName()
+ " only works if scoreBounderEnabled (" + scoreBounderEnabled + ") is true.");
}
}
@Override
public int compare(ExhaustiveSearchNode a, ExhaustiveSearchNode b) {
// Investigate better optimistic bound first (ignore initScore to avoid depth first ordering)
int optimisticBoundComparison = a.getOptimisticBound().compareTo(b.getOptimisticBound());
if (optimisticBoundComparison < 0) {
return -1;
} else if (optimisticBoundComparison > 0) {
return 1;
}
// Investigate better score first
int scoreComparison = a.getScore().toInitializedScore().compareTo(b.getScore().toInitializedScore());
if (scoreComparison < 0) {
return -1;
} else if (scoreComparison > 0) {
return 1;
}
// Investigate deeper first
int aDepth = a.getDepth();
int bDepth = b.getDepth();
if (aDepth < bDepth) {
return -1;
} else if (aDepth > bDepth) {
return 1;
}
// Investigate higher parent breadth index first (to reduce on the churn on workingSolution)
long aParentBreadth = a.getParentBreadth();
long bParentBreadth = b.getParentBreadth();
if (aParentBreadth < bParentBreadth) {
return -1;
} else if (aParentBreadth > bParentBreadth) {
return 1;
}
// Investigate lower breadth index first (to respect ValueSortingManner)
return Long.compare(b.getBreadth(), a.getBreadth());
}
}