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A set of mathematical utilities

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/**
 * Copyright (c) 2017, RTE (http://www.rte-france.com)
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 * SPDX-License-Identifier: MPL-2.0
 */
package com.powsybl.math.matrix;

/**
 * LU decomposition utility class. As some decomposition implementation may allocate resources that need to be released
 * a try-with-resource block has to be used to ensure correct resource management.
 *  * try (LUDecomposition decomposition = m.decomposeLU()) {
 *     decomposition.solve(...)
 * }
 * 
 *
 * @see https://en.wikipedia.org/wiki/LU_decomposition
 *
 * @author Geoffroy Jamgotchian {@literal }
 */
public interface LUDecomposition extends AutoCloseable {

    /**
     * Method to call when matrix has been updated to refresh LU decomposition so that new data can be taken into
     * account in next {@link #solve(double[])} or {@link #solve(DenseMatrix)}.
     * @param allowIncrementalUpdate allow decomposition incremental update (so using previous decomposition values)
     */
    void update(boolean allowIncrementalUpdate);

    /**
     * Method to call when matrix has been updated to refresh LU decomposition so that new data can be taken into
     * account in next {@link #solve(double[])} or {@link #solve(DenseMatrix)}.
     */
    default void update() {
        update(true);
    }

    /**
     * Solve A * x = b where b is a column vector.
     *
     * @param b a column vector
     */
    void solve(double[] b);

    /**
     * Solve AT * x = b where b is a column vector.
     *
     * @param b a column vector
     */
    void solveTransposed(double[] b);

    /**
     * Solve A * x = b where b is a dense matrix.
     *
     * @param b a matrix
     */
    void solve(DenseMatrix b);

    /**
     * Solve AT * x = b where b is a dense matrix.
     *
     * @param b a matrix
     */
    void solveTransposed(DenseMatrix b);

    /**
     * {@inheritDoc}
     */
    @Override
    void close();
}