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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.
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 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
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 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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package org.openimaj.knn.approximate;

import java.util.Arrays;
import java.util.List;

import org.openimaj.citation.annotation.Reference;
import org.openimaj.citation.annotation.ReferenceType;
import org.openimaj.knn.ShortNearestNeighbours;
import org.openimaj.knn.NearestNeighboursFactory;
import org.openimaj.util.pair.*;

/**
 * Fast Nearest-Neighbours for short data using an ensemble of Best-Bin-First KDTrees. 
 * <p>
 * Implementation inspired by http://www.robots.ox.ac.uk/~vgg/software/fastann/
 * 
 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
 */
@Reference(
        type = ReferenceType.Inproceedings,
        author = { "Marius Muja", "David G. Lowe" },
        title = "Fast Approximate Nearest Neighbors with Automatic Algorithm Configuration",
        year = "2009",
        booktitle = "International Conference on Computer Vision Theory and Application VISSAPP'09)",
        pages = { "331", "340" },
        publisher = "INSTICC Press"
)
public class ShortNearestNeighboursKDTree extends ShortNearestNeighbours {
    /**
         * {@link NearestNeighboursFactory} for producing
         * {@link ShortNearestNeighboursKDTree}s.
         * 
         * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
         */
    public static final class Factory implements NearestNeighboursFactory<ShortNearestNeighboursKDTree, short[]> {
        int ntrees;
        int nchecks;
        
        /**
         * Construct the factory the default number of trees and checks.
         */
        public Factory() {
            this.ntrees = ShortNearestNeighboursKDTree.DEFAULT_NTREES;
            this.nchecks = ShortNearestNeighboursKDTree.DEFAULT_NCHECKS;
        }
        
        /**
         * Construct the factory the given number of trees and checks.
         * 
                 * @param ntrees 
                 *          the number of trees 
         * @param nchecks 
         *          the number of checks during search
         */
        public Factory(int ntrees, int nchecks) {
            this.ntrees = ntrees;
            this.nchecks = nchecks;
        }
        
        @Override
        public ShortNearestNeighboursKDTree create(short[][] data) {
            return new ShortNearestNeighboursKDTree(data, ntrees, nchecks);
        }
    }
    
    /**
         * The default number of checks performed during search when in exact mode.
         */
        public static final int DEFAULT_NCHECKS = 768;

        /**
         * The default number of kdtrees when not in exact mode.
         */
        public static final int DEFAULT_NTREES = 8;
    
        /** The ensemble of KDTrees */
        public final ShortKDTreeEnsemble kdt;
        
        /** The number of checks */
    public final int nchecks;
        
        /** 
         * Construct the ShortNearestNeighboursKDTree with the given options.
         * 
         * @param pnts the data
         * @param ntrees the number of trees 
         * @param nchecks the number of checks during search
         */
    public ShortNearestNeighboursKDTree(final short [][] pnts, int ntrees, int nchecks) {
        kdt = new ShortKDTreeEnsemble(pnts, ntrees);
        this.nchecks = nchecks;
    }
    
        @Override
        public int numDimensions() {
                return kdt.pnts[0].length;
        }

        @Override
        public int size() {
                return kdt.pnts.length;
        }

        @Override
        public void searchKNN(short[][] qus, int K, int[][] argmins, float[][] mins) {
                // Fix for when the user asks for too many points.
        K = Math.min(K, kdt.pnts.length);
     
        IntFloatPair[] nns = new IntFloatPair[K];
        final int N = qus.length;
        
        for (int n=0; n < N; ++n) {
            kdt.search(qus[n], K, nns, nchecks);
            for (int k=0; k < K; ++k) {
                argmins[n][k] = nns[k].first;
                mins[n][k] = nns[k].second;
            }
        }
        }

        @Override
        public void searchNN(short[][] qus, int[] argmins, float[] mins) {
                final int N = qus.length;
                IntFloatPair [] nn = new IntFloatPair[1];
                
                for (int n=0; n < N; ++n) {
            kdt.search(qus[n], 1, nn, nchecks);
            
            argmins[n] = nn[0].first;
            mins[n] = nn[0].second;
        }
        }
        
        @Override
        public void searchKNN(List<short[]> qus, int K, int[][] argmins, float[][] mins) {
                // Fix for when the user asks for too many points.
        K = Math.min(K, kdt.pnts.length);
     
        IntFloatPair[] nns = new IntFloatPair[K];
        final int N = qus.size();
        
        for (int n=0; n < N; ++n) {
            kdt.search(qus.get(n), K, nns, nchecks);
            for (int k=0; k < K; ++k) {
                argmins[n][k] = nns[k].first;
                mins[n][k] = nns[k].second;
            }
        }
        }

        @Override
        public void searchNN(List<short[]> qus, int[] argmins, float[] mins) {
                final int N = qus.size();
                IntFloatPair [] nn = new IntFloatPair[1];
                
                for (int n=0; n < N; ++n) {
            kdt.search(qus.get(n), 1, nn, nchecks);
            
            argmins[n] = nn[0].first;
            mins[n] = nn[0].second;
        }
        }
        
        @Override
        public List<IntFloatPair> searchKNN(short[] query, int K) {
                // Fix for when the user asks for too many points.
                K = Math.min(K, kdt.pnts.length);

                final IntFloatPair[] nns = new IntFloatPair[K];

                kdt.search(query, K, nns, nchecks);

                return Arrays.asList(nns);
        }

        @Override
        public IntFloatPair searchNN(short[] query) {
                final IntFloatPair[] nn = new IntFloatPair[1];

                kdt.search(query, 1, nn, nchecks);
                
                return nn[0];
        }
}