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Java example source code file (IterativeLinearSolver.java)

This example Java source code file (IterativeLinearSolver.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

dimensionmismatchexception, iterationmanager, iterativelinearsolver, maxcountexceededexception, nonsquareoperatorexception, nullargumentexception, reallinearoperator, realvector

The IterativeLinearSolver.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.linear;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.util.IterationManager;
import org.apache.commons.math3.util.MathUtils;

/**
 * This abstract class defines an iterative solver for the linear system A
 * · x = b. In what follows, the <em>residual r is defined as r = b
 * - A · x, where A is the linear operator of the linear system, b is the
 * right-hand side vector, and x the current estimate of the solution.
 *
 * @since 3.0
 */
public abstract class IterativeLinearSolver {

    /** The object in charge of managing the iterations. */
    private final IterationManager manager;

    /**
     * Creates a new instance of this class, with default iteration manager.
     *
     * @param maxIterations the maximum number of iterations
     */
    public IterativeLinearSolver(final int maxIterations) {
        this.manager = new IterationManager(maxIterations);
    }

    /**
     * Creates a new instance of this class, with custom iteration manager.
     *
     * @param manager the custom iteration manager
     * @throws NullArgumentException if {@code manager} is {@code null}
     */
    public IterativeLinearSolver(final IterationManager manager)
        throws NullArgumentException {
        MathUtils.checkNotNull(manager);
        this.manager = manager;
    }

    /**
     * Performs all dimension checks on the parameters of
     * {@link #solve(RealLinearOperator, RealVector, RealVector) solve} and
     * {@link #solveInPlace(RealLinearOperator, RealVector, RealVector) solveInPlace},
     * and throws an exception if one of the checks fails.
     *
     * @param a the linear operator A of the system
     * @param b the right-hand side vector
     * @param x0 the initial guess of the solution
     * @throws NullArgumentException if one of the parameters is {@code null}
     * @throws NonSquareOperatorException if {@code a} is not square
     * @throws DimensionMismatchException if {@code b} or {@code x0} have
     * dimensions inconsistent with {@code a}
     */
    protected static void checkParameters(final RealLinearOperator a,
        final RealVector b, final RealVector x0) throws
        NullArgumentException, NonSquareOperatorException,
        DimensionMismatchException {
        MathUtils.checkNotNull(a);
        MathUtils.checkNotNull(b);
        MathUtils.checkNotNull(x0);
        if (a.getRowDimension() != a.getColumnDimension()) {
            throw new NonSquareOperatorException(a.getRowDimension(),
                                                       a.getColumnDimension());
        }
        if (b.getDimension() != a.getRowDimension()) {
            throw new DimensionMismatchException(b.getDimension(),
                                                 a.getRowDimension());
        }
        if (x0.getDimension() != a.getColumnDimension()) {
            throw new DimensionMismatchException(x0.getDimension(),
                                                 a.getColumnDimension());
        }
    }

    /**
     * Returns the iteration manager attached to this solver.
     *
     * @return the manager
     */
    public IterationManager getIterationManager() {
        return manager;
    }

    /**
     * Returns an estimate of the solution to the linear system A · x =
     * b.
     *
     * @param a the linear operator A of the system
     * @param b the right-hand side vector
     * @return a new vector containing the solution
     * @throws NullArgumentException if one of the parameters is {@code null}
     * @throws NonSquareOperatorException if {@code a} is not square
     * @throws DimensionMismatchException if {@code b} has dimensions
     * inconsistent with {@code a}
     * @throws MaxCountExceededException at exhaustion of the iteration count,
     * unless a custom
     * {@link org.apache.commons.math3.util.Incrementor.MaxCountExceededCallback callback}
     * has been set at construction of the {@link IterationManager}
     */
    public RealVector solve(final RealLinearOperator a, final RealVector b)
        throws NullArgumentException, NonSquareOperatorException,
        DimensionMismatchException, MaxCountExceededException {
        MathUtils.checkNotNull(a);
        final RealVector x = new ArrayRealVector(a.getColumnDimension());
        x.set(0.);
        return solveInPlace(a, b, x);
    }

    /**
     * Returns an estimate of the solution to the linear system A · x =
     * b.
     *
     * @param a the linear operator A of the system
     * @param b the right-hand side vector
     * @param x0 the initial guess of the solution
     * @return a new vector containing the solution
     * @throws NullArgumentException if one of the parameters is {@code null}
     * @throws NonSquareOperatorException if {@code a} is not square
     * @throws DimensionMismatchException if {@code b} or {@code x0} have
     * dimensions inconsistent with {@code a}
     * @throws MaxCountExceededException at exhaustion of the iteration count,
     * unless a custom
     * {@link org.apache.commons.math3.util.Incrementor.MaxCountExceededCallback callback}
     * has been set at construction of the {@link IterationManager}
     */
    public RealVector solve(RealLinearOperator a, RealVector b, RealVector x0)
        throws NullArgumentException, NonSquareOperatorException,
        DimensionMismatchException, MaxCountExceededException {
        MathUtils.checkNotNull(x0);
        return solveInPlace(a, b, x0.copy());
    }

    /**
     * Returns an estimate of the solution to the linear system A · x =
     * b. The solution is computed in-place (initial guess is modified).
     *
     * @param a the linear operator A of the system
     * @param b the right-hand side vector
     * @param x0 initial guess of the solution
     * @return a reference to {@code x0} (shallow copy) updated with the
     * solution
     * @throws NullArgumentException if one of the parameters is {@code null}
     * @throws NonSquareOperatorException if {@code a} is not square
     * @throws DimensionMismatchException if {@code b} or {@code x0} have
     * dimensions inconsistent with {@code a}
     * @throws MaxCountExceededException at exhaustion of the iteration count,
     * unless a custom
     * {@link org.apache.commons.math3.util.Incrementor.MaxCountExceededCallback callback}
     * has been set at construction of the {@link IterationManager}
     */
    public abstract RealVector solveInPlace(RealLinearOperator a, RealVector b,
        RealVector x0) throws NullArgumentException, NonSquareOperatorException,
        DimensionMismatchException, MaxCountExceededException;
}

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