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Java example source code file (OpenMapRealMatrix.java)

This example Java source code file (OpenMapRealMatrix.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

abstractrealmatrix, blockrealmatrix, classcastexception, matrixdimensionmismatchexception, notstrictlypositiveexception, numberistoolargeexception, openinttodoublehashmap, openmaprealmatrix, outofrangeexception, override, serializable, sparserealmatrix

The OpenMapRealMatrix.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 java.io.Serializable;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.apache.commons.math3.exception.NumberIsTooLargeException;
import org.apache.commons.math3.exception.OutOfRangeException;
import org.apache.commons.math3.util.OpenIntToDoubleHashMap;

/**
 * Sparse matrix implementation based on an open addressed map.
 *
 * <p>
 *  Caveat: This implementation assumes that, for any {@code x},
 *  the equality {@code x * 0d == 0d} holds. But it is is not true for
 *  {@code NaN}. Moreover, zero entries will lose their sign.
 *  Some operations (that involve {@code NaN} and/or infinities) may
 *  thus give incorrect results.
 * </p>
 * @since 2.0
 */
public class OpenMapRealMatrix extends AbstractRealMatrix
    implements SparseRealMatrix, Serializable {
    /** Serializable version identifier. */
    private static final long serialVersionUID = -5962461716457143437L;
    /** Number of rows of the matrix. */
    private final int rows;
    /** Number of columns of the matrix. */
    private final int columns;
    /** Storage for (sparse) matrix elements. */
    private final OpenIntToDoubleHashMap entries;

    /**
     * Build a sparse matrix with the supplied row and column dimensions.
     *
     * @param rowDimension Number of rows of the matrix.
     * @param columnDimension Number of columns of the matrix.
     * @throws NotStrictlyPositiveException if row or column dimension is not
     * positive.
     * @throws NumberIsTooLargeException if the total number of entries of the
     * matrix is larger than {@code Integer.MAX_VALUE}.
     */
    public OpenMapRealMatrix(int rowDimension, int columnDimension)
        throws NotStrictlyPositiveException, NumberIsTooLargeException {
        super(rowDimension, columnDimension);
        long lRow = rowDimension;
        long lCol = columnDimension;
        if (lRow * lCol >= Integer.MAX_VALUE) {
            throw new NumberIsTooLargeException(lRow * lCol, Integer.MAX_VALUE, false);
        }
        this.rows = rowDimension;
        this.columns = columnDimension;
        this.entries = new OpenIntToDoubleHashMap(0.0);
    }

    /**
     * Build a matrix by copying another one.
     *
     * @param matrix matrix to copy.
     */
    public OpenMapRealMatrix(OpenMapRealMatrix matrix) {
        this.rows = matrix.rows;
        this.columns = matrix.columns;
        this.entries = new OpenIntToDoubleHashMap(matrix.entries);
    }

    /** {@inheritDoc} */
    @Override
    public OpenMapRealMatrix copy() {
        return new OpenMapRealMatrix(this);
    }

    /**
     * {@inheritDoc}
     *
     * @throws NumberIsTooLargeException if the total number of entries of the
     * matrix is larger than {@code Integer.MAX_VALUE}.
     */
    @Override
    public OpenMapRealMatrix createMatrix(int rowDimension, int columnDimension)
        throws NotStrictlyPositiveException, NumberIsTooLargeException {
        return new OpenMapRealMatrix(rowDimension, columnDimension);
    }

    /** {@inheritDoc} */
    @Override
    public int getColumnDimension() {
        return columns;
    }

    /**
     * Compute the sum of this matrix and {@code m}.
     *
     * @param m Matrix to be added.
     * @return {@code this} + {@code m}.
     * @throws MatrixDimensionMismatchException if {@code m} is not the same
     * size as {@code this}.
     */
    public OpenMapRealMatrix add(OpenMapRealMatrix m)
        throws MatrixDimensionMismatchException {

        MatrixUtils.checkAdditionCompatible(this, m);

        final OpenMapRealMatrix out = new OpenMapRealMatrix(this);
        for (OpenIntToDoubleHashMap.Iterator iterator = m.entries.iterator(); iterator.hasNext();) {
            iterator.advance();
            final int row = iterator.key() / columns;
            final int col = iterator.key() - row * columns;
            out.setEntry(row, col, getEntry(row, col) + iterator.value());
        }

        return out;

    }

    /** {@inheritDoc} */
    @Override
    public OpenMapRealMatrix subtract(final RealMatrix m)
        throws MatrixDimensionMismatchException {
        try {
            return subtract((OpenMapRealMatrix) m);
        } catch (ClassCastException cce) {
            return (OpenMapRealMatrix) super.subtract(m);
        }
    }

    /**
     * Subtract {@code m} from this matrix.
     *
     * @param m Matrix to be subtracted.
     * @return {@code this} - {@code m}.
     * @throws MatrixDimensionMismatchException if {@code m} is not the same
     * size as {@code this}.
     */
    public OpenMapRealMatrix subtract(OpenMapRealMatrix m)
        throws MatrixDimensionMismatchException {
        MatrixUtils.checkAdditionCompatible(this, m);

        final OpenMapRealMatrix out = new OpenMapRealMatrix(this);
        for (OpenIntToDoubleHashMap.Iterator iterator = m.entries.iterator(); iterator.hasNext();) {
            iterator.advance();
            final int row = iterator.key() / columns;
            final int col = iterator.key() - row * columns;
            out.setEntry(row, col, getEntry(row, col) - iterator.value());
        }

        return out;
    }

    /**
     * {@inheritDoc}
     *
     * @throws NumberIsTooLargeException if {@code m} is an
     * {@code OpenMapRealMatrix}, and the total number of entries of the product
     * is larger than {@code Integer.MAX_VALUE}.
     */
    @Override
    public RealMatrix multiply(final RealMatrix m)
        throws DimensionMismatchException, NumberIsTooLargeException {
        try {
            return multiply((OpenMapRealMatrix) m);
        } catch (ClassCastException cce) {

            MatrixUtils.checkMultiplicationCompatible(this, m);

            final int outCols = m.getColumnDimension();
            final BlockRealMatrix out = new BlockRealMatrix(rows, outCols);
            for (OpenIntToDoubleHashMap.Iterator iterator = entries.iterator(); iterator.hasNext();) {
                iterator.advance();
                final double value = iterator.value();
                final int key      = iterator.key();
                final int i        = key / columns;
                final int k        = key % columns;
                for (int j = 0; j < outCols; ++j) {
                    out.addToEntry(i, j, value * m.getEntry(k, j));
                }
            }

            return out;
        }
    }

    /**
     * Postmultiply this matrix by {@code m}.
     *
     * @param m Matrix to postmultiply by.
     * @return {@code this} * {@code m}.
     * @throws DimensionMismatchException if the number of rows of {@code m}
     * differ from the number of columns of {@code this} matrix.
     * @throws NumberIsTooLargeException if the total number of entries of the
     * product is larger than {@code Integer.MAX_VALUE}.
     */
    public OpenMapRealMatrix multiply(OpenMapRealMatrix m)
        throws DimensionMismatchException, NumberIsTooLargeException {
        // Safety check.
        MatrixUtils.checkMultiplicationCompatible(this, m);

        final int outCols = m.getColumnDimension();
        OpenMapRealMatrix out = new OpenMapRealMatrix(rows, outCols);
        for (OpenIntToDoubleHashMap.Iterator iterator = entries.iterator(); iterator.hasNext();) {
            iterator.advance();
            final double value = iterator.value();
            final int key      = iterator.key();
            final int i        = key / columns;
            final int k        = key % columns;
            for (int j = 0; j < outCols; ++j) {
                final int rightKey = m.computeKey(k, j);
                if (m.entries.containsKey(rightKey)) {
                    final int outKey = out.computeKey(i, j);
                    final double outValue =
                        out.entries.get(outKey) + value * m.entries.get(rightKey);
                    if (outValue == 0.0) {
                        out.entries.remove(outKey);
                    } else {
                        out.entries.put(outKey, outValue);
                    }
                }
            }
        }

        return out;
    }

    /** {@inheritDoc} */
    @Override
    public double getEntry(int row, int column) throws OutOfRangeException {
        MatrixUtils.checkRowIndex(this, row);
        MatrixUtils.checkColumnIndex(this, column);
        return entries.get(computeKey(row, column));
    }

    /** {@inheritDoc} */
    @Override
    public int getRowDimension() {
        return rows;
    }

    /** {@inheritDoc} */
    @Override
    public void setEntry(int row, int column, double value)
        throws OutOfRangeException {
        MatrixUtils.checkRowIndex(this, row);
        MatrixUtils.checkColumnIndex(this, column);
        if (value == 0.0) {
            entries.remove(computeKey(row, column));
        } else {
            entries.put(computeKey(row, column), value);
        }
    }

    /** {@inheritDoc} */
    @Override
    public void addToEntry(int row, int column, double increment)
        throws OutOfRangeException {
        MatrixUtils.checkRowIndex(this, row);
        MatrixUtils.checkColumnIndex(this, column);
        final int key = computeKey(row, column);
        final double value = entries.get(key) + increment;
        if (value == 0.0) {
            entries.remove(key);
        } else {
            entries.put(key, value);
        }
    }

    /** {@inheritDoc} */
    @Override
    public void multiplyEntry(int row, int column, double factor)
        throws OutOfRangeException {
        MatrixUtils.checkRowIndex(this, row);
        MatrixUtils.checkColumnIndex(this, column);
        final int key = computeKey(row, column);
        final double value = entries.get(key) * factor;
        if (value == 0.0) {
            entries.remove(key);
        } else {
            entries.put(key, value);
        }
    }

    /**
     * Compute the key to access a matrix element
     * @param row row index of the matrix element
     * @param column column index of the matrix element
     * @return key within the map to access the matrix element
     */
    private int computeKey(int row, int column) {
        return row * columns + column;
    }


}

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