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With inspiration from other libraries
/*
* 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.
*
* A linear constraint has one of the forms:
*
* - c1x1 + ... cnxn = v
* - c1x1 + ... cnxn <= v
* - c1x1 + ... cnxn >= v
* - l1x1 + ... lnxn + lcst =
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst <=
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst >=
* r1x1 + ... rnxn + rcst
*
* The ci, 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.
*
*
* @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.
*
* A linear constraint with a single linear equation has one of the forms:
*
* - c1x1 + ... cnxn = v
* - c1x1 + ... cnxn <= v
* - c1x1 + ... cnxn >= v
*
*
* @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.
*
* A linear constraint with a single linear equation has one of the forms:
*
* - c1x1 + ... cnxn = v
* - c1x1 + ... cnxn <= v
* - c1x1 + ... cnxn >= v
*
*
* @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.
*
* A linear constraint with two linear equation has one of the forms:
*
* - l1x1 + ... lnxn + lcst =
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst <=
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst >=
* r1x1 + ... rnxn + rcst
*
*
* @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.
*
* A linear constraint with two linear equation has one of the forms:
*
* - l1x1 + ... lnxn + lcst =
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst <=
* r1x1 + ... rnxn + rcst
* - l1x1 + ... lnxn + lcst >=
* r1x1 + ... rnxn + rcst
*
*
* @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);
}
}