MOEZipfDistribution.java

package ldbc.snb.datagen.generator.distribution;

import ldbc.snb.datagen.generator.DatagenParams;
import ldbc.snb.datagen.generator.distribution.utils.Bucket;
import ldbc.snb.datagen.generator.distribution.utils.BucketedDistribution;
import org.apache.hadoop.conf.Configuration;

import java.util.ArrayList;
import java.util.Random;

/**
 * Created by aprat on 4/03/15.
 */
public class MOEZipfDistribution implements DegreeDistribution  {

    private org.apache.commons.math3.distribution.ZipfDistribution zipf_;
    private double ALPHA_ = 1.7;
    private double DELTA_ = 1.5;
    private Random random_;

    public void initialize(Configuration conf) {
        ALPHA_ = conf.getDouble("ldbc.snb.datagen.generator.distribution.MOEZipfDistribution.alpha",ALPHA_);
        DELTA_ = conf.getDouble("ldbc.snb.datagen.generator.distribution.MOEZipfDistribution.delta",DELTA_);
        zipf_ = new org.apache.commons.math3.distribution.ZipfDistribution(5000, ALPHA_);
        random_ = new Random();
    }

    public void reset (long seed) {
        random_.setSeed(seed);
        zipf_.reseedRandomGenerator(seed);
    }

    public long nextDegree(){
        double prob = random_.nextDouble();
        double prime = (prob * DELTA_)/(1 + prob*(DELTA_ - 1));
        long ret = zipf_.inverseCumulativeProbability(prime);
        return ret;
    }

}