001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.lsh.functions;
031
032import org.openimaj.util.comparator.DistanceComparator;
033import org.openimaj.util.hash.HashFunctionFactory;
034
035import cern.jet.random.engine.MersenneTwister;
036
037/**
038 * A factory for producing {@link RandomisedHashFunction}s.
039 * 
040 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
041 * 
042 * @param <OBJECT>
043 *            type of object being hashed
044 */
045public abstract class RandomisedHashFunctionFactory<OBJECT>
046                implements
047                        HashFunctionFactory<OBJECT>
048{
049        protected MersenneTwister rng;
050        protected int ndims;
051
052        /**
053         * * @param ndims number of dimensions of data
054         * 
055         * @param rng
056         *            the random number generator
057         */
058        protected RandomisedHashFunctionFactory(int ndims, MersenneTwister rng) {
059                this.rng = rng;
060                this.ndims = ndims;
061        }
062
063        /**
064         * @return a distance comparator that produces distances of the type
065         *         approximated by this hashing scheme
066         */
067        public abstract DistanceComparator<OBJECT> distanceFunction();
068}