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 */ 017 package org.apache.commons.math3.optim.nonlinear.scalar; 018 019 import java.util.Collections; 020 import java.util.List; 021 import java.util.ArrayList; 022 import java.util.Comparator; 023 import org.apache.commons.math3.exception.NotStrictlyPositiveException; 024 import org.apache.commons.math3.exception.NullArgumentException; 025 import org.apache.commons.math3.random.RandomVectorGenerator; 026 import org.apache.commons.math3.optim.BaseMultiStartMultivariateOptimizer; 027 import org.apache.commons.math3.optim.PointValuePair; 028 029 /** 030 * Multi-start optimizer. 031 * 032 * This class wraps an optimizer in order to use it several times in 033 * turn with different starting points (trying to avoid being trapped 034 * in a local extremum when looking for a global one). 035 * 036 * @version $Id$ 037 * @since 3.0 038 */ 039 public class MultiStartMultivariateOptimizer 040 extends BaseMultiStartMultivariateOptimizer<PointValuePair> { 041 /** Underlying optimizer. */ 042 private final MultivariateOptimizer optimizer; 043 /** Found optima. */ 044 private final List<PointValuePair> optima = new ArrayList<PointValuePair>(); 045 046 /** 047 * Create a multi-start optimizer from a single-start optimizer. 048 * 049 * @param optimizer Single-start optimizer to wrap. 050 * @param starts Number of starts to perform. 051 * If {@code starts == 1}, the result will be same as if {@code optimizer} 052 * is called directly. 053 * @param generator Random vector generator to use for restarts. 054 * @throws NullArgumentException if {@code optimizer} or {@code generator} 055 * is {@code null}. 056 * @throws NotStrictlyPositiveException if {@code starts < 1}. 057 */ 058 public MultiStartMultivariateOptimizer(final MultivariateOptimizer optimizer, 059 final int starts, 060 final RandomVectorGenerator generator) 061 throws NullArgumentException, 062 NotStrictlyPositiveException { 063 super(optimizer, starts, generator); 064 this.optimizer = optimizer; 065 } 066 067 /** 068 * {@inheritDoc} 069 */ 070 @Override 071 public PointValuePair[] getOptima() { 072 Collections.sort(optima, getPairComparator()); 073 return optima.toArray(new PointValuePair[0]); 074 } 075 076 /** 077 * {@inheritDoc} 078 */ 079 @Override 080 protected void store(PointValuePair optimum) { 081 optima.add(optimum); 082 } 083 084 /** 085 * {@inheritDoc} 086 */ 087 @Override 088 protected void clear() { 089 optima.clear(); 090 } 091 092 /** 093 * @return a comparator for sorting the optima. 094 */ 095 private Comparator<PointValuePair> getPairComparator() { 096 return new Comparator<PointValuePair>() { 097 public int compare(final PointValuePair o1, 098 final PointValuePair o2) { 099 if (o1 == null) { 100 return (o2 == null) ? 0 : 1; 101 } else if (o2 == null) { 102 return -1; 103 } 104 final double v1 = o1.getValue(); 105 final double v2 = o2.getValue(); 106 return (optimizer.getGoalType() == GoalType.MINIMIZE) ? 107 Double.compare(v1, v2) : Double.compare(v2, v1); 108 } 109 }; 110 } 111 }