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 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.commons.math3.optim.linear;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import org.apache.commons.math3.analysis.MultivariateFunction;
import org.apache.commons.math3.linear.MatrixUtils;
import org.apache.commons.math3.linear.RealVector;
import org.apache.commons.math3.linear.ArrayRealVector;
import org.apache.commons.math3.optim.OptimizationData;

An objective function for a linear optimization problem.

A linear objective function has one the form:
c1x1 + ... cnxn + d

The ci and d are the coefficients of the equation,
the xi are the coordinates of the current point.

Since:
2.0/**
 * An objective function for a linear optimization problem.
 * <p>
 * A linear objective function has one the form:
 * <pre>
 * c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> + d
 * </pre>
 * The c<sub>i</sub> and d are the coefficients of the equation,
 * the x<sub>i</sub> are the coordinates of the current point.
 * </p>
 *
 * @since 2.0
 */
public class LinearObjectiveFunction
    implements MultivariateFunction,
               OptimizationData,
               Serializable {
    
Serializable version identifier. /** Serializable version identifier. */
    private static final long serialVersionUID = -4531815507568396090L;
    
Coefficients of the linear equation (ci). /** Coefficients of the linear equation (c<sub>i</sub>). */
    private final transient RealVector coefficients;
    
Constant term of the linear equation. /** Constant term of the linear equation. */
    private final double constantTerm;

    
Params:
coefficients – Coefficients for the linear equation being optimized.
constantTerm – Constant term of the linear equation./**
     * @param coefficients Coefficients for the linear equation being optimized.
     * @param constantTerm Constant term of the linear equation.
     */
    public LinearObjectiveFunction(double[] coefficients, double constantTerm) {
        this(new ArrayRealVector(coefficients), constantTerm);
    }

    
Params:
coefficients – Coefficients for the linear equation being optimized.
constantTerm – Constant term of the linear equation./**
     * @param coefficients Coefficients for the linear equation being optimized.
     * @param constantTerm Constant term of the linear equation.
     */
    public LinearObjectiveFunction(RealVector coefficients, double constantTerm) {
        this.coefficients = coefficients;
        this.constantTerm = constantTerm;
    }

    
Gets the coefficients of the linear equation being optimized.
Returns:
coefficients of the linear equation being optimized./**
     * Gets the coefficients of the linear equation being optimized.
     *
     * @return coefficients of the linear equation being optimized.
     */
    public RealVector getCoefficients() {
        return coefficients;
    }

    
Gets the constant of the linear equation being optimized.
Returns:
constant of the linear equation being optimized./**
     * Gets the constant of the linear equation being optimized.
     *
     * @return constant of the linear equation being optimized.
     */
    public double getConstantTerm() {
        return constantTerm;
    }

    
Computes the value of the linear equation at the current point.
Params:
point – Point at which linear equation must be evaluated.
Returns:
the value of the linear equation at the current point./**
     * Computes the value of the linear equation at the current point.
     *
     * @param point Point at which linear equation must be evaluated.
     * @return the value of the linear equation at the current point.
     */
    public double value(final double[] point) {
        return value(new ArrayRealVector(point, false));
    }

    
Computes the value of the linear equation at the current point.
Params:
point – Point at which linear equation must be evaluated.
Returns:
the value of the linear equation at the current point./**
     * Computes the value of the linear equation at the current point.
     *
     * @param point Point at which linear equation must be evaluated.
     * @return the value of the linear equation at the current point.
     */
    public double value(final RealVector point) {
        return coefficients.dotProduct(point) + constantTerm;
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (other instanceof LinearObjectiveFunction) {
            LinearObjectiveFunction rhs = (LinearObjectiveFunction) other;
          return (constantTerm == rhs.constantTerm) && coefficients.equals(rhs.coefficients);
        }

        return false;
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override
    public int hashCode() {
        return Double.valueOf(constantTerm).hashCode() ^ coefficients.hashCode();
    }

    
Serialize the instance.
Params:
oos – stream where object should be written
Throws:
IOException – if object cannot be written to stream/**
     * Serialize the instance.
     * @param oos stream where object should be written
     * @throws IOException if object cannot be written to stream
     */
    private void writeObject(ObjectOutputStream oos)
        throws IOException {
        oos.defaultWriteObject();
        MatrixUtils.serializeRealVector(coefficients, oos);
    }

    
Deserialize the instance.
Params:
ois – stream from which the object should be read
Throws:
ClassNotFoundException – if a class in the stream cannot be found
IOException – if object cannot be read from the stream/**
     * Deserialize the instance.
     * @param ois stream from which the object should be read
     * @throws ClassNotFoundException if a class in the stream cannot be found
     * @throws IOException if object cannot be read from the stream
     */
    private void readObject(ObjectInputStream ois)
      throws ClassNotFoundException, IOException {
        ois.defaultReadObject();
        MatrixUtils.deserializeRealVector(this, "coefficients", ois);
    }
}