001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.math4.legacy.optim.nonlinear.scalar; 018 019import java.util.ArrayList; 020import java.util.Collections; 021import java.util.Comparator; 022import java.util.List; 023import java.util.function.Supplier; 024 025import org.apache.commons.math4.legacy.optim.BaseMultiStartMultivariateOptimizer; 026import org.apache.commons.math4.legacy.optim.PointValuePair; 027 028/** 029 * Multi-start optimizer. 030 * 031 * This class wraps an optimizer in order to use it several times in 032 * turn with different starting points (trying to avoid being trapped 033 * in a local extremum when looking for a global one). 034 * 035 * @since 3.0 036 */ 037public class MultiStartMultivariateOptimizer 038 extends BaseMultiStartMultivariateOptimizer<PointValuePair> { 039 /** Underlying optimizer. */ 040 private final MultivariateOptimizer optimizer; 041 /** Found optima. */ 042 private final List<PointValuePair> optima = new ArrayList<>(); 043 044 /** 045 * Create a multi-start optimizer from a single-start optimizer. 046 * 047 * @param optimizer Single-start optimizer to wrap. 048 * @param starts Number of starts to perform. 049 * If {@code starts == 1}, the result will be same as if {@code optimizer} 050 * is called directly. 051 * @param generator Generator to use for restarts. 052 * @throws org.apache.commons.math4.legacy.exception.NullArgumentException NullArgumentException if {@code optimizer} or {@code generator} 053 * is {@code null}. 054 * @throws org.apache.commons.math4.legacy.exception.NotStrictlyPositiveException NotStrictlyPositiveException if {@code starts < 1}. 055 */ 056 public MultiStartMultivariateOptimizer(final MultivariateOptimizer optimizer, 057 final int starts, 058 final Supplier<double[]> generator) { 059 super(optimizer, starts, generator); 060 this.optimizer = optimizer; 061 } 062 063 /** 064 * {@inheritDoc} 065 */ 066 @Override 067 public PointValuePair[] getOptima() { 068 Collections.sort(optima, getPairComparator()); 069 return optima.toArray(new PointValuePair[0]); 070 } 071 072 /** 073 * {@inheritDoc} 074 */ 075 @Override 076 protected void store(PointValuePair optimum) { 077 optima.add(optimum); 078 } 079 080 /** 081 * {@inheritDoc} 082 */ 083 @Override 084 protected void clear() { 085 optima.clear(); 086 } 087 088 /** 089 * @return a comparator for sorting the optima. 090 */ 091 private Comparator<PointValuePair> getPairComparator() { 092 return new Comparator<PointValuePair>() { 093 /** {@inheritDoc} */ 094 @Override 095 public int compare(final PointValuePair o1, 096 final PointValuePair o2) { 097 if (o1 == null) { 098 return (o2 == null) ? 0 : 1; 099 } else if (o2 == null) { 100 return -1; 101 } 102 final double v1 = o1.getValue(); 103 final double v2 = o2.getValue(); 104 return (optimizer.getGoalType() == GoalType.MINIMIZE) ? 105 Double.compare(v1, v2) : Double.compare(v2, v1); 106 } 107 }; 108 } 109}