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Java example source code file (SparseFieldMatrix.java)

This example Java source code file (SparseFieldMatrix.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

abstractfieldmatrix, fieldelement, openinttofieldhashmap, override, sparsefieldmatrix

The SparseFieldMatrix.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.Field;
import org.apache.commons.math3.FieldElement;
import org.apache.commons.math3.util.OpenIntToFieldHashMap;

/**
 * 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>
 * @param <T> the type of the field elements
 * @since 2.0
 */
public class SparseFieldMatrix<T extends FieldElement extends AbstractFieldMatrix {

    /** Storage for (sparse) matrix elements. */
    private final OpenIntToFieldHashMap<T> entries;
    /** Row dimension. */
    private final int rows;
    /** Column dimension. */
    private final int columns;

    /**
     * Create a matrix with no data.
     *
     * @param field Field to which the elements belong.
     */
    public SparseFieldMatrix(final Field<T> field) {
        super(field);
        rows = 0;
        columns= 0;
        entries = new OpenIntToFieldHashMap<T>(field);
    }

    /**
     * Create a new SparseFieldMatrix<T> with the supplied row and column
     * dimensions.
     *
     * @param field Field to which the elements belong.
     * @param rowDimension Number of rows in the new matrix.
     * @param columnDimension Number of columns in the new matrix.
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if row or column dimension is not positive.
     */
    public SparseFieldMatrix(final Field<T> field,
                             final int rowDimension, final int columnDimension) {
        super(field, rowDimension, columnDimension);
        this.rows = rowDimension;
        this.columns = columnDimension;
        entries = new OpenIntToFieldHashMap<T>(field);
    }

    /**
     * Copy constructor.
     *
     * @param other Instance to copy.
     */
    public SparseFieldMatrix(SparseFieldMatrix<T> other) {
        super(other.getField(), other.getRowDimension(), other.getColumnDimension());
        rows = other.getRowDimension();
        columns = other.getColumnDimension();
        entries = new OpenIntToFieldHashMap<T>(other.entries);
    }

    /**
     * Generic copy constructor.
     *
     * @param other Instance to copy.
     */
    public SparseFieldMatrix(FieldMatrix<T> other){
        super(other.getField(), other.getRowDimension(), other.getColumnDimension());
        rows = other.getRowDimension();
        columns = other.getColumnDimension();
        entries = new OpenIntToFieldHashMap<T>(getField());
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                setEntry(i, j, other.getEntry(i, j));
            }
        }
    }

    /** {@inheritDoc} */
    @Override
    public void addToEntry(int row, int column, T increment) {
        checkRowIndex(row);
        checkColumnIndex(column);
        final int key = computeKey(row, column);
        final T value = entries.get(key).add(increment);
        if (getField().getZero().equals(value)) {
            entries.remove(key);
        } else {
            entries.put(key, value);
        }
    }

    /** {@inheritDoc} */
    @Override
    public FieldMatrix<T> copy() {
        return new SparseFieldMatrix<T>(this);
    }

    /** {@inheritDoc} */
    @Override
    public FieldMatrix<T> createMatrix(int rowDimension, int columnDimension) {
        return new SparseFieldMatrix<T>(getField(), rowDimension, columnDimension);
    }

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

    /** {@inheritDoc} */
    @Override
    public T getEntry(int row, int column) {
        checkRowIndex(row);
        checkColumnIndex(column);
        return entries.get(computeKey(row, column));
    }

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

    /** {@inheritDoc} */
    @Override
    public void multiplyEntry(int row, int column, T factor) {
        checkRowIndex(row);
        checkColumnIndex(column);
        final int key = computeKey(row, column);
        final T value = entries.get(key).multiply(factor);
        if (getField().getZero().equals(value)) {
            entries.remove(key);
        } else {
            entries.put(key, value);
        }

    }

    /** {@inheritDoc} */
    @Override
    public void setEntry(int row, int column, T value) {
        checkRowIndex(row);
        checkColumnIndex(column);
        if (getField().getZero().equals(value)) {
            entries.remove(computeKey(row, column));
        } else {
            entries.put(computeKey(row, column), 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 the key within the map to access the matrix element.
     */
    private int computeKey(int row, int column) {
        return row * columns + column;
    }
}

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