info.debatty.java.lsh.examples.SimpleLSHMinHashExample Maven / Gradle / Ivy

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/*
 * The MIT License
 *
 * Copyright 2015 tibo.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package info.debatty.java.lsh.examples;

import info.debatty.java.lsh.LSHMinHash;
import java.util.Random;

/**
 *
 * @author tibo
 */
public class SimpleLSHMinHashExample {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // proportion of 0's in the vectors
        // if the vectors are dense (lots of 1's), the average jaccard similarity
        // will be very high (especially for large vectors), and LSH
        // won't be able to distinguish them
        // as a result, all vectors will be binned in the same bucket...
        double sparsity = 0.75;
        
        // Number of sets
        int count = 10000;
        
        // Size of vectors
        int n = 100;
        
        // LSH parameters
        // the number of stages is also sometimes called thge number of bands
        int stages = 2;
        
        // Attention: to get relevant results, the number of elements per bucket
        // should be at least 100
        int buckets = 10;
        
        // Let's generate some random sets
        boolean[][] vectors = new boolean[count][n];
        Random rand = new Random();
        
        for (int i = 0; i < count; i++) {
            for (int j = 0; j < n; j++) {
                vectors[i][j] = rand.nextDouble() > sparsity;
            }
        }
        
        // Create and configure LSH algorithm
        LSHMinHash lsh = new LSHMinHash(stages, buckets, n);
        
        int[][] counts = new int[stages][buckets];
        
        // Perform hashing
        for (boolean[] vector : vectors) {
            int[] hash = lsh.hash(vector);
            
            for (int i = 0; i < hash.length; i++) {
                counts[i][hash[i]]++;
            }
            
            print(vector);
            System.out.print(" : ");
            print(hash);
            System.out.print("\n");
        }
        
        System.out.println("Number of elements per bucket at each stage:");
        for (int i = 0; i < stages; i++) {
            print(counts[i]);
            System.out.print("\n");
        }
    }
    
    static void print(int[] array) {
        System.out.print("[");
        for (int v : array) {
            System.out.print("" + v + " ");
        }
        System.out.print("]");
    }
    
    static void print(boolean[] array) {
        System.out.print("[");
        for (boolean v : array) {
            System.out.print(v ? "1" : "0");
        }
        System.out.print("]");
    }
}