1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.math.optimization.linear; 19 20 import java.io.IOException; 21 import java.io.ObjectInputStream; 22 import java.io.ObjectOutputStream; 23 import java.io.Serializable; 24 25 import org.apache.commons.math.linear.MatrixUtils; 26 import org.apache.commons.math.linear.RealVector; 27 import org.apache.commons.math.linear.ArrayRealVector; 28 29 /** 30 * An objective function for a linear optimization problem. 31 * <p> 32 * A linear objective function has one the form: 33 * <pre> 34 * c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> + d 35 * </pre> 36 * The c<sub>i</sub> and d are the coefficients of the equation, 37 * the x<sub>i</sub> are the coordinates of the current point. 38 * </p> 39 * @version $Revision: 922713 $ $Date: 2010-03-14 02:26:13 +0100 (dim. 14 mars 2010) $ 40 * @since 2.0 41 */ 42 public class LinearObjectiveFunction implements Serializable { 43 44 /** Serializable version identifier. */ 45 private static final long serialVersionUID = -4531815507568396090L; 46 47 /** Coefficients of the constraint (c<sub>i</sub>). */ 48 private final transient RealVector coefficients; 49 50 /** Constant term of the linear equation. */ 51 private final double constantTerm; 52 53 /** 54 * @param coefficients The coefficients for the linear equation being optimized 55 * @param constantTerm The constant term of the linear equation 56 */ 57 public LinearObjectiveFunction(double[] coefficients, double constantTerm) { 58 this(new ArrayRealVector(coefficients), constantTerm); 59 } 60 61 /** 62 * @param coefficients The coefficients for the linear equation being optimized 63 * @param constantTerm The constant term of the linear equation 64 */ 65 public LinearObjectiveFunction(RealVector coefficients, double constantTerm) { 66 this.coefficients = coefficients; 67 this.constantTerm = constantTerm; 68 } 69 70 /** 71 * Get the coefficients of the linear equation being optimized. 72 * @return coefficients of the linear equation being optimized 73 */ 74 public RealVector getCoefficients() { 75 return coefficients; 76 } 77 78 /** 79 * Get the constant of the linear equation being optimized. 80 * @return constant of the linear equation being optimized 81 */ 82 public double getConstantTerm() { 83 return constantTerm; 84 } 85 86 /** 87 * Compute the value of the linear equation at the current point 88 * @param point point at which linear equation must be evaluated 89 * @return value of the linear equation at the current point 90 */ 91 public double getValue(final double[] point) { 92 return coefficients.dotProduct(point) + constantTerm; 93 } 94 95 /** 96 * Compute the value of the linear equation at the current point 97 * @param point point at which linear equation must be evaluated 98 * @return value of the linear equation at the current point 99 */ 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 instanceof LinearObjectiveFunction) { 113 LinearObjectiveFunction rhs = (LinearObjectiveFunction) other; 114 return (constantTerm == rhs.constantTerm) && coefficients.equals(rhs.coefficients); 115 } 116 117 return false; 118 } 119 120 /** {@inheritDoc} */ 121 @Override 122 public int hashCode() { 123 return Double.valueOf(constantTerm).hashCode() ^ coefficients.hashCode(); 124 } 125 126 /** Serialize the instance. 127 * @param oos stream where object should be written 128 * @throws IOException if object cannot be written to stream 129 */ 130 private void writeObject(ObjectOutputStream oos) 131 throws IOException { 132 oos.defaultWriteObject(); 133 MatrixUtils.serializeRealVector(coefficients, oos); 134 } 135 136 /** Deserialize the instance. 137 * @param ois stream from which the object should be read 138 * @throws ClassNotFoundException if a class in the stream cannot be found 139 * @throws IOException if object cannot be read from the stream 140 */ 141 private void readObject(ObjectInputStream ois) 142 throws ClassNotFoundException, IOException { 143 ois.defaultReadObject(); 144 MatrixUtils.deserializeRealVector(this, "coefficients", ois); 145 } 146 147 } 148
