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Java example source code file (LinearConstraint.java)

This example Java source code file (LinearConstraint.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arrayrealvector, classnotfoundexception, ioexception, linearconstraint, override, realvector, relationship, serializable

The LinearConstraint.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * 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
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
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.linear.MatrixUtils;
import org.apache.commons.math3.linear.RealVector;
import org.apache.commons.math3.linear.ArrayRealVector;

/**
 * A linear constraint for a linear optimization problem.
 * <p>
 * A linear constraint has one of the forms:
 * <ul>
 *   <li>c1x1 + ... cnxn = v
 *   <li>c1x1 + ... cnxn <= v
 *   <li>c1x1 + ... cnxn >= v
 *   <li>l1x1 + ... lnxn + lcst =
 *       r<sub>1x1 + ... rnxn + rcst
 *   <li>l1x1 + ... lnxn + lcst <=
 *       r<sub>1x1 + ... rnxn + rcst
 *   <li>l1x1 + ... lnxn + lcst >=
 *       r<sub>1x1 + ... rnxn + rcst
 * </ul>
 * The c<sub>i, li or ri are the coefficients of the constraints, the xi
 * are the coordinates of the current point and v is the value of the constraint.
 * </p>
 *
 * @since 2.0
 */
public class LinearConstraint implements Serializable {
    /** Serializable version identifier. */
    private static final long serialVersionUID = -764632794033034092L;
    /** Coefficients of the constraint (left hand side). */
    private final transient RealVector coefficients;
    /** Relationship between left and right hand sides (=, <=, >=). */
    private final Relationship relationship;
    /** Value of the constraint (right hand side). */
    private final double value;

    /**
     * Build a constraint involving a single linear equation.
     * <p>
     * A linear constraint with a single linear equation has one of the forms:
     * <ul>
     *   <li>c1x1 + ... cnxn = v
     *   <li>c1x1 + ... cnxn <= v
     *   <li>c1x1 + ... cnxn >= v
     * </ul>
     * </p>
     * @param coefficients The coefficients of the constraint (left hand side)
     * @param relationship The type of (in)equality used in the constraint
     * @param value The value of the constraint (right hand side)
     */
    public LinearConstraint(final double[] coefficients,
                            final Relationship relationship,
                            final double value) {
        this(new ArrayRealVector(coefficients), relationship, value);
    }

    /**
     * Build a constraint involving a single linear equation.
     * <p>
     * A linear constraint with a single linear equation has one of the forms:
     * <ul>
     *   <li>c1x1 + ... cnxn = v
     *   <li>c1x1 + ... cnxn <= v
     *   <li>c1x1 + ... cnxn >= v
     * </ul>
     * </p>
     * @param coefficients The coefficients of the constraint (left hand side)
     * @param relationship The type of (in)equality used in the constraint
     * @param value The value of the constraint (right hand side)
     */
    public LinearConstraint(final RealVector coefficients,
                            final Relationship relationship,
                            final double value) {
        this.coefficients = coefficients;
        this.relationship = relationship;
        this.value        = value;
    }

    /**
     * Build a constraint involving two linear equations.
     * <p>
     * A linear constraint with two linear equation has one of the forms:
     * <ul>
     *   <li>l1x1 + ... lnxn + lcst =
     *       r<sub>1x1 + ... rnxn + rcst
     *   <li>l1x1 + ... lnxn + lcst <=
     *       r<sub>1x1 + ... rnxn + rcst
     *   <li>l1x1 + ... lnxn + lcst >=
     *       r<sub>1x1 + ... rnxn + rcst
     * </ul>
     * </p>
     * @param lhsCoefficients The coefficients of the linear expression on the left hand side of the constraint
     * @param lhsConstant The constant term of the linear expression on the left hand side of the constraint
     * @param relationship The type of (in)equality used in the constraint
     * @param rhsCoefficients The coefficients of the linear expression on the right hand side of the constraint
     * @param rhsConstant The constant term of the linear expression on the right hand side of the constraint
     */
    public LinearConstraint(final double[] lhsCoefficients, final double lhsConstant,
                            final Relationship relationship,
                            final double[] rhsCoefficients, final double rhsConstant) {
        double[] sub = new double[lhsCoefficients.length];
        for (int i = 0; i < sub.length; ++i) {
            sub[i] = lhsCoefficients[i] - rhsCoefficients[i];
        }
        this.coefficients = new ArrayRealVector(sub, false);
        this.relationship = relationship;
        this.value        = rhsConstant - lhsConstant;
    }

    /**
     * Build a constraint involving two linear equations.
     * <p>
     * A linear constraint with two linear equation has one of the forms:
     * <ul>
     *   <li>l1x1 + ... lnxn + lcst =
     *       r<sub>1x1 + ... rnxn + rcst
     *   <li>l1x1 + ... lnxn + lcst <=
     *       r<sub>1x1 + ... rnxn + rcst
     *   <li>l1x1 + ... lnxn + lcst >=
     *       r<sub>1x1 + ... rnxn + rcst
     * </ul>
     * </p>
     * @param lhsCoefficients The coefficients of the linear expression on the left hand side of the constraint
     * @param lhsConstant The constant term of the linear expression on the left hand side of the constraint
     * @param relationship The type of (in)equality used in the constraint
     * @param rhsCoefficients The coefficients of the linear expression on the right hand side of the constraint
     * @param rhsConstant The constant term of the linear expression on the right hand side of the constraint
     */
    public LinearConstraint(final RealVector lhsCoefficients, final double lhsConstant,
                            final Relationship relationship,
                            final RealVector rhsCoefficients, final double rhsConstant) {
        this.coefficients = lhsCoefficients.subtract(rhsCoefficients);
        this.relationship = relationship;
        this.value        = rhsConstant - lhsConstant;
    }

    /**
     * Gets the coefficients of the constraint (left hand side).
     *
     * @return the coefficients of the constraint (left hand side).
     */
    public RealVector getCoefficients() {
        return coefficients;
    }

    /**
     * Gets the relationship between left and right hand sides.
     *
     * @return the relationship between left and right hand sides.
     */
    public Relationship getRelationship() {
        return relationship;
    }

    /**
     * Gets the value of the constraint (right hand side).
     *
     * @return the value of the constraint (right hand side).
     */
    public double getValue() {
        return value;
    }

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

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

    /**
     * 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.
     * @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);
    }
}

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