/*
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*/
/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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package org.openimaj.knn;

import org.openimaj.feature.DoubleFVComparator;

import org.openimaj.util.pair.IntDoublePair;

/**
 * Abstract base class for k-nearest-neighbour calculations with double[] data.
 * 
 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
 */
public abstract class DoubleNearestNeighbours implements NearestNeighbours<double[], double[], IntDoublePair> {
        /**
         * Static method to find the sum-squared distance between
         * a query vector and each of a set of points. Results are stored 
         * in the dsq_out array, much must have the same length as the number
         * of points.
         * @param qu The query vector.
         * @param pnts The points to compare against.
         * @param dsq_out The resultant distances. 
         */
        public static void distanceFunc(final double [] qu, final double [][] pnts, double [] dsq_out) {
                final int N = pnts.length;
                final int D = pnts[0].length;
                
                for (int n=0; n < N; ++n) {
                        dsq_out[n] = 0;
                        for (int d=0; d<D; ++d) {
                                dsq_out[n] += (qu[d] - pnts[n][d]) * (qu[d] - pnts[n][d]);
                        }
                }
        }
        
        /**
         * Static method to find the sum-squared distance between
         * a query vector and a point. 
         
         * @param qu The query vector.
         * @param pnt The point to compare against.
         * @return The resultant distance.
         */
        public static double distanceFunc(final double [] qu, final double [] pnt) {
                final int D = pnt.length;
                
                double dsq_out = 0;
                for (int d=0; d<D; ++d) {
                        dsq_out += (qu[d] - pnt[d]) * (qu[d] - pnt[d]);
                }
                
                return dsq_out;
        }

        /**
         * Static method to find a distance between
         * a query vector and a point.
         *
         * @param distance the distance measure
         * @param qu The query vector.
         * @param pnt The point to compare against.
         * @return The resultant distance. 
         */
        public static double distanceFunc(final DoubleFVComparator distance, final double [] qu, final double [] pnt) {
                if (distance == null) {
                        return distanceFunc(qu, pnt);
                }
                
                if (distance.isDistance()) {
                        return (double) distance.compare(qu, pnt);
                } else {
            return - (double) distance.compare(qu, pnt);
                }
        }
        
        /**
         * Static method to find a distance between
         * a query vector and each of a set of points. Results are stored 
         * in the dsq_out array, much must have the same length as the number
         * of points.
         * @param distance the distance measure
         * @param qu The query vector.
         * @param pnts The points to compare against.
         * @param dsq_out The resultant distances. 
         */
        public static void distanceFunc(final DoubleFVComparator distance, final double [] qu, final double [][] pnts, double [] dsq_out) {
                if (distance == null) {
                        distanceFunc(qu, pnts, dsq_out);
                        return;
                }
                
                final int N = pnts.length;

                if (distance.isDistance()) {
                        for (int n=0; n < N; ++n) {
                                dsq_out[n] = (double) distance.compare(qu, pnts[n]);
                        }       
                } else {
                        for (int n=0; n < N; ++n) {
                                dsq_out[n] = - (double) distance.compare(qu, pnts[n]);
                        }
                }
        }
        
        /**
         * Get the number of dimensions of each vector in the dataset
         * 
         * @return the number of dimensions
         */
        public abstract int numDimensions();
}