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/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *  this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *  contributors may be used to endorse or promote products derived from this
 *  software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openimaj.math.matrix;

import ch.akuhn.matrix.KuhnMatrix;
import ch.akuhn.matrix.Vector;

/**
 * A diagonal specialization of Adrian Kuhn's {@link KuhnMatrix}.
 * 
 * @author Sina Samangooei ([email protected])
 */
public class DiagonalMatrix extends KuhnMatrix {

    private final double[] vals;

    /**
     * New empty matrix with 0s down the diagonals
     * @param rowcol
     */
    public DiagonalMatrix(int rowcol) {
        vals = new double[rowcol];
    }

    /**
     * New empty matrix with val down the diagonals
     * @param rowcol
     * @param val 
     */
    public DiagonalMatrix(int rowcol, double val) {
        vals = new double[rowcol];
        for (int i = 0; i < vals.length; i++) {
            vals[i] = val;
        }
    }

    /**
     * Diagonal version of the matrix handed
     * @param arr
     */
    public DiagonalMatrix(double[][] arr) {
        this(Math.min(arr.length, arr[0].length));
        for (int i = 0; i < vals.length; i++) {
            vals[i] = arr[i][i];
        }
    }

    /**
     * @param mat
     */
    public DiagonalMatrix(KuhnMatrix mat) {
        this(Math.min(mat.rowCount(), mat.columnCount()));
        for (int i = 0; i < vals.length; i++) {
            vals[i] = mat.get(i, i);
        }
    }

    @Override
    public Vector mult(Vector x) {
        double[] y = new double[this.columnCount()];
        for (int i = 0; i < y.length; i++) {
            y[i] = vals[i] * x.get(i);
        }
        return Vector.wrap(y);
    }

    @Override
    public Vector transposeMultiply(Vector x) {
        return mult(x);
    }

    @Override
    public Vector transposeNonTransposeMultiply(Vector x) {
        double[] y = new double[this.columnCount()];
        for (int i = 0; i < y.length; i++) {
            double val = vals[i];
            y[i] = val * val * x.get(i);
        }
        return Vector.wrap(y);
    }

    @Override
    public int columnCount() {
        return vals.length;
    }

    @Override
    public double get(int row, int column) {
        if (row != column) {
            return 0.0;
        }
        return vals[row];
    }

    @Override
    public double put(int row, int column, double value) {
        if (row == column) {
            return vals[row] = value;
        }
        return 0.0;
    }

    @Override
    public int rowCount() {
        return vals.length;
    }

    @Override
    public int used() {
        return vals.length;
    }

    /**
     * @param rowcol
     * @return a matrix of ones in the diagonal
     */
    public static DiagonalMatrix zeros(int rowcol) {
        return fill(rowcol, 0.0);
    }

    /**
     * @param rowcol
     * @return a matrix of ones in the diagonal
     */
    public static DiagonalMatrix ones(int rowcol) {
        return fill(rowcol, 1.0);
    }

    /**
     * @param rowcol
     * @param d
     * @return a matrix with d in the diagonal
     */
    public static DiagonalMatrix fill(int rowcol, double d) {
        DiagonalMatrix ret = new DiagonalMatrix(rowcol);
        for (int i = 0; i < rowcol; i++) {
            ret.vals[i] = d;
        }
        return ret;
    }

    /**
     * @return the diagonals
     */
    public double[] getVals() {
        return vals;
    }

    @Override
    public KuhnMatrix newInstance(int rows, int cols) {
        return new DiagonalMatrix(rows);
    }
}