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.analysis.integration.gauss; 018 019import java.util.Map; 020import java.util.TreeMap; 021import org.apache.commons.math3.util.Pair; 022import org.apache.commons.math3.exception.DimensionMismatchException; 023import org.apache.commons.math3.exception.NotStrictlyPositiveException; 024import org.apache.commons.math3.exception.util.LocalizedFormats; 025 026/** 027 * Base class for rules that determines the integration nodes and their 028 * weights. 029 * Subclasses must implement the {@link #computeRule(int) computeRule} method. 030 * 031 * @param <T> Type of the number used to represent the points and weights of 032 * the quadrature rules. 033 * 034 * @since 3.1 035 */ 036public abstract class BaseRuleFactory<T extends Number> { 037 /** List of points and weights, indexed by the order of the rule. */ 038 private final Map<Integer, Pair<T[], T[]>> pointsAndWeights 039 = new TreeMap<Integer, Pair<T[], T[]>>(); 040 /** Cache for double-precision rules. */ 041 private final Map<Integer, Pair<double[], double[]>> pointsAndWeightsDouble 042 = new TreeMap<Integer, Pair<double[], double[]>>(); 043 044 /** 045 * Gets a copy of the quadrature rule with the given number of integration 046 * points. 047 * 048 * @param numberOfPoints Number of integration points. 049 * @return a copy of the integration rule. 050 * @throws NotStrictlyPositiveException if {@code numberOfPoints < 1}. 051 * @throws DimensionMismatchException if the elements of the rule pair do not 052 * have the same length. 053 */ 054 public Pair<double[], double[]> getRule(int numberOfPoints) 055 throws NotStrictlyPositiveException, DimensionMismatchException { 056 057 if (numberOfPoints <= 0) { 058 throw new NotStrictlyPositiveException(LocalizedFormats.NUMBER_OF_POINTS, 059 numberOfPoints); 060 } 061 062 // Try to obtain the rule from the cache. 063 Pair<double[], double[]> cached = pointsAndWeightsDouble.get(numberOfPoints); 064 065 if (cached == null) { 066 // Rule not computed yet. 067 068 // Compute the rule. 069 final Pair<T[], T[]> rule = getRuleInternal(numberOfPoints); 070 cached = convertToDouble(rule); 071 072 // Cache it. 073 pointsAndWeightsDouble.put(numberOfPoints, cached); 074 } 075 076 // Return a copy. 077 return new Pair<double[], double[]>(cached.getFirst().clone(), 078 cached.getSecond().clone()); 079 } 080 081 /** 082 * Gets a rule. 083 * Synchronization ensures that rules will be computed and added to the 084 * cache at most once. 085 * The returned rule is a reference into the cache. 086 * 087 * @param numberOfPoints Order of the rule to be retrieved. 088 * @return the points and weights corresponding to the given order. 089 * @throws DimensionMismatchException if the elements of the rule pair do not 090 * have the same length. 091 */ 092 protected synchronized Pair<T[], T[]> getRuleInternal(int numberOfPoints) 093 throws DimensionMismatchException { 094 final Pair<T[], T[]> rule = pointsAndWeights.get(numberOfPoints); 095 if (rule == null) { 096 addRule(computeRule(numberOfPoints)); 097 // The rule should be available now. 098 return getRuleInternal(numberOfPoints); 099 } 100 return rule; 101 } 102 103 /** 104 * Stores a rule. 105 * 106 * @param rule Rule to be stored. 107 * @throws DimensionMismatchException if the elements of the pair do not 108 * have the same length. 109 */ 110 protected void addRule(Pair<T[], T[]> rule) throws DimensionMismatchException { 111 if (rule.getFirst().length != rule.getSecond().length) { 112 throw new DimensionMismatchException(rule.getFirst().length, 113 rule.getSecond().length); 114 } 115 116 pointsAndWeights.put(rule.getFirst().length, rule); 117 } 118 119 /** 120 * Computes the rule for the given order. 121 * 122 * @param numberOfPoints Order of the rule to be computed. 123 * @return the computed rule. 124 * @throws DimensionMismatchException if the elements of the pair do not 125 * have the same length. 126 */ 127 protected abstract Pair<T[], T[]> computeRule(int numberOfPoints) 128 throws DimensionMismatchException; 129 130 /** 131 * Converts the from the actual {@code Number} type to {@code double} 132 * 133 * @param <T> Type of the number used to represent the points and 134 * weights of the quadrature rules. 135 * @param rule Points and weights. 136 * @return points and weights as {@code double}s. 137 */ 138 private static <T extends Number> Pair<double[], double[]> convertToDouble(Pair<T[], T[]> rule) { 139 final T[] pT = rule.getFirst(); 140 final T[] wT = rule.getSecond(); 141 142 final int len = pT.length; 143 final double[] pD = new double[len]; 144 final double[] wD = new double[len]; 145 146 for (int i = 0; i < len; i++) { 147 pD[i] = pT[i].doubleValue(); 148 wD[i] = wT[i].doubleValue(); 149 } 150 151 return new Pair<double[], double[]>(pD, wD); 152 } 153}