edu.ucla.sspace.matrix.SymmetricIntMatrix Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of sspace-wordsi Show documentation

The S-Space Package is a collection of algorithms for building Semantic Spaces as well as a highly-scalable library for designing new distributional semantics algorithms. Distributional algorithms process text corpora and represent the semantic for words as high dimensional feature vectors. This package also includes matrices, vectors, and numerous clustering algorithms. These approaches are known by many names, such as word spaces, semantic spaces, or distributed semantics and rest upon the Distributional Hypothesis: words that appear in similar contexts have similar meanings.

The newest version!

/*
 * Copyright 2011 David Jurgens
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.matrix;

import edu.ucla.sspace.vector.DenseVector;
import edu.ucla.sspace.vector.DoubleVector;
import edu.ucla.sspace.vector.Vector;
import edu.ucla.sspace.vector.Vectors;


/**
 * A symmetric dense matrix that only stores the values of the lower triangular.
 * This class only records changes values where row > col.  For all other
 * values, the row and column values are swapped and then the backing matrix is
 * updated.  
 *
 * 
 *
 * The primary benfit of this class is for storing large symmetric matrices in
 * half of the memory.
 *
 * @author David Jurgens
 */
public class SymmetricIntMatrix extends AbstractMatrix 
        implements java.io.Serializable {

    private static final long serialVersionUID = 1L;

    private final int[][] values;

    private final int rows;

    private final int columns;

    /**
     * Constructs a new {@link SymmetricMatrix} with the specified dimensions.
     */
    public SymmetricIntMatrix(int rows, int columns) {
        this.rows = rows;
        this.columns = columns;

        values = new int[rows][];
        for (int r = 0; r < rows; ++r)
            values[r] = new int[r+1];
    }
    
    /**
     * {@inheritDoc}
     */
    public int columns() {
        return columns;
    }

    /**
     * {@inheritDoc}
     */
    @Override public double get(int row, int column) {
        // Swap the ordering so only the lower triangular is read
        if (column > row) {
            int tmp = column;
            column = row;
            row = tmp;
        }
        return values[row][column];
    }

    /**
     * {@inheritDoc}
     */
    public DoubleVector getColumnVector(int column) {
        DenseVector col = new DenseVector(rows);
        for (int r = 0; r < rows; ++r)
            col.set(r, get(r, column));
        return col;
    }
    
    /**
     * {@inheritDoc}
     */
    public DoubleVector getRowVector(int row) {
        DenseVector rowVec = new DenseVector(columns);
        for (int c = 0; c < columns; ++c)
            rowVec.set(c, get(row, c));
        return rowVec;
    }

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

    /**
     * {@inheritDoc}
     */
    @Override public void set(int row, int column, double val) {
        // Swap the ordering so only the lower triangular is written to
        if (column > row) {
            int tmp = column;
            column = row;
            row = tmp;
        }
        values[row][column] = (int) val;
    }
}