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 */ 017 018 package org.apache.commons.math.optimization.linear; 019 020 import java.io.IOException; 021 import java.io.ObjectInputStream; 022 import java.io.ObjectOutputStream; 023 import java.io.Serializable; 024 025 import org.apache.commons.math.linear.MatrixUtils; 026 import org.apache.commons.math.linear.RealVector; 027 import org.apache.commons.math.linear.ArrayRealVector; 028 029 /** 030 * An objective function for a linear optimization problem. 031 * <p> 032 * A linear objective function has one the form: 033 * <pre> 034 * c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> + d 035 * </pre> 036 * The c<sub>i</sub> and d are the coefficients of the equation, 037 * the x<sub>i</sub> are the coordinates of the current point. 038 * </p> 039 * @version $Revision: 783702 $ $Date: 2009-06-11 04:54:02 -0400 (Thu, 11 Jun 2009) $ 040 * @since 2.0 041 */ 042 public class LinearObjectiveFunction implements Serializable { 043 044 /** Serializable version identifier. */ 045 private static final long serialVersionUID = -4531815507568396090L; 046 047 /** Coefficients of the constraint (c<sub>i</sub>). */ 048 private final transient RealVector coefficients; 049 050 /** Constant term of the linear equation. */ 051 private final double constantTerm; 052 053 /** 054 * @param coefficients The coefficients for the linear equation being optimized 055 * @param constantTerm The constant term of the linear equation 056 */ 057 public LinearObjectiveFunction(double[] coefficients, double constantTerm) { 058 this(new ArrayRealVector(coefficients), constantTerm); 059 } 060 061 /** 062 * @param coefficients The coefficients for the linear equation being optimized 063 * @param constantTerm The constant term of the linear equation 064 */ 065 public LinearObjectiveFunction(RealVector coefficients, double constantTerm) { 066 this.coefficients = coefficients; 067 this.constantTerm = constantTerm; 068 } 069 070 /** 071 * Get the coefficients of the linear equation being optimized. 072 * @return coefficients of the linear equation being optimized 073 */ 074 public RealVector getCoefficients() { 075 return coefficients; 076 } 077 078 /** 079 * Get the constant of the linear equation being optimized. 080 * @return constant of the linear equation being optimized 081 */ 082 public double getConstantTerm() { 083 return constantTerm; 084 } 085 086 /** 087 * Compute the value of the linear equation at the current point 088 * @param point point at which linear equation must be evaluated 089 * @return value of the linear equation at the current point 090 */ 091 public double getValue(final double[] point) { 092 return coefficients.dotProduct(point) + constantTerm; 093 } 094 095 /** 096 * Compute the value of the linear equation at the current point 097 * @param point point at which linear equation must be evaluated 098 * @return value of the linear equation at the current point 099 */ 100 public double getValue(final RealVector point) { 101 return coefficients.dotProduct(point) + constantTerm; 102 } 103 104 /** {@inheritDoc} */ 105 @Override 106 public boolean equals(Object other) { 107 108 if (this == other) { 109 return true; 110 } 111 112 if (other == null) { 113 return false; 114 } 115 116 try { 117 118 LinearObjectiveFunction rhs = (LinearObjectiveFunction) other; 119 return (constantTerm == rhs.constantTerm) && coefficients.equals(rhs.coefficients); 120 121 } catch (ClassCastException ex) { 122 // ignore exception 123 return false; 124 } 125 126 } 127 128 /** {@inheritDoc} */ 129 @Override 130 public int hashCode() { 131 return Double.valueOf(constantTerm).hashCode() ^ coefficients.hashCode(); 132 } 133 134 /** Serialize the instance. 135 * @param oos stream where object should be written 136 * @throws IOException if object cannot be written to stream 137 */ 138 private void writeObject(ObjectOutputStream oos) 139 throws IOException { 140 oos.defaultWriteObject(); 141 MatrixUtils.serializeRealVector(coefficients, oos); 142 } 143 144 /** Deserialize the instance. 145 * @param ois stream from which the object should be read 146 * @throws ClassNotFoundException if a class in the stream cannot be found 147 * @throws IOException if object cannot be read from the stream 148 */ 149 private void readObject(ObjectInputStream ois) 150 throws ClassNotFoundException, IOException { 151 ois.defaultReadObject(); 152 MatrixUtils.deserializeRealVector(this, "coefficients", ois); 153 } 154 155 }