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/* ---------------------------------------------------------------------
 * Numenta Platform for Intelligent Computing (NuPIC)
 * Copyright (C) 2014, Numenta, Inc.  Unless you have an agreement
 * with Numenta, Inc., for a separate license for this software code, the
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 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero Public License for more details.
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 * You should have received a copy of the GNU Affero Public License
 * along with this program.  If not, see http://www.gnu.org/licenses.
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package org.numenta.nupic.util;

/**
 * Allows storage of array data in sparse form, meaning that the indexes
 * of the data stored are maintained while empty indexes are not. This allows
 * savings in memory and computational efficiency because iterative algorithms
 * need only query indexes containing valid data. The dimensions of matrix defined
 * at construction time and immutable - matrix fixed size data structure.
 * 
 * @author David Ray
 * @author Jose Luis Martin
 *
 * @param 
 */
public interface SparseMatrix extends FlatMatrix{

    /**
     * Returns a sorted array of occupied indexes.
     * @return  a sorted array of occupied indexes.
     */
    int[] getSparseIndices();

    /**
     * Returns an array of all the flat indexes that can be 
     * computed from the current configuration.
     * @return
     */
    int[] get1DIndexes();

    /**
     * Uses the specified {@link TypeFactory} to return an array
     * filled with the specified object type, according this {@code SparseMatrix}'s 
     * configured dimensions
     * 
     * @param factory   a factory to make a specific type
     * @return  the dense array
     */
    T[] asDense(TypeFactory factory);

}