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.math3.optim.nonlinear.scalar; 018 019import java.util.Collections; 020import java.util.List; 021import java.util.ArrayList; 022import java.util.Comparator; 023import org.apache.commons.math3.exception.NotStrictlyPositiveException; 024import org.apache.commons.math3.exception.NullArgumentException; 025import org.apache.commons.math3.random.RandomVectorGenerator; 026import org.apache.commons.math3.optim.BaseMultiStartMultivariateOptimizer; 027import 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 * @since 3.0 037 */ 038public class MultiStartMultivariateOptimizer 039 extends BaseMultiStartMultivariateOptimizer<PointValuePair> { 040 /** Underlying optimizer. */ 041 private final MultivariateOptimizer optimizer; 042 /** Found optima. */ 043 private final List<PointValuePair> optima = new ArrayList<PointValuePair>(); 044 045 /** 046 * Create a multi-start optimizer from a single-start optimizer. 047 * 048 * @param optimizer Single-start optimizer to wrap. 049 * @param starts Number of starts to perform. 050 * If {@code starts == 1}, the result will be same as if {@code optimizer} 051 * is called directly. 052 * @param generator Random vector generator to use for restarts. 053 * @throws NullArgumentException if {@code optimizer} or {@code generator} 054 * is {@code null}. 055 * @throws NotStrictlyPositiveException if {@code starts < 1}. 056 */ 057 public MultiStartMultivariateOptimizer(final MultivariateOptimizer optimizer, 058 final int starts, 059 final RandomVectorGenerator generator) 060 throws NullArgumentException, 061 NotStrictlyPositiveException { 062 super(optimizer, starts, generator); 063 this.optimizer = optimizer; 064 } 065 066 /** 067 * {@inheritDoc} 068 */ 069 @Override 070 public PointValuePair[] getOptima() { 071 Collections.sort(optima, getPairComparator()); 072 return optima.toArray(new PointValuePair[0]); 073 } 074 075 /** 076 * {@inheritDoc} 077 */ 078 @Override 079 protected void store(PointValuePair optimum) { 080 optima.add(optimum); 081 } 082 083 /** 084 * {@inheritDoc} 085 */ 086 @Override 087 protected void clear() { 088 optima.clear(); 089 } 090 091 /** 092 * @return a comparator for sorting the optima. 093 */ 094 private Comparator<PointValuePair> getPairComparator() { 095 return new Comparator<PointValuePair>() { 096 /** {@inheritDoc} */ 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}