com.ibm.bi.dml.runtime.util.PoissonPRNGenerator.java Source code

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Here is the source code for com.ibm.bi.dml.runtime.util.PoissonPRNGenerator.java

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/**
 * (C) Copyright IBM Corp. 2010, 2015
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
*/

package com.ibm.bi.dml.runtime.util;

import org.apache.commons.math3.distribution.PoissonDistribution;
import org.apache.commons.math3.random.SynchronizedRandomGenerator;
import org.apache.commons.math3.random.Well1024a;

/**
 * Class that can generate a stream of random numbers from Poisson
 * distribution with specified mean. 
 */

public class PoissonPRNGenerator extends PRNGenerator {
    PoissonDistribution _pdist = null;
    double _mean = Double.NaN;

    private static final double DEFAULT_MEAN = 1.0;

    public PoissonPRNGenerator() {
        // default mean and default seed
        super();
        _mean = 1.0;
        setup(_mean, seed);
    }

    public PoissonPRNGenerator(double mean) {
        // default seed
        super();
        _mean = mean;
        setup(_mean, seed);
    }

    public PoissonPRNGenerator(long sd) {
        // default mean
        super();
        setup(DEFAULT_MEAN, sd);
    }

    public void setup(double mean, long sd) {
        seed = sd;

        SynchronizedRandomGenerator srg = new SynchronizedRandomGenerator(new Well1024a());
        srg.setSeed(seed);
        _pdist = new PoissonDistribution(srg, _mean, PoissonDistribution.DEFAULT_EPSILON,
                PoissonDistribution.DEFAULT_MAX_ITERATIONS);
    }

    @Override
    public void setSeed(long sd) {
        setup(_mean, sd);
    }

    public void setMean(double mean) {
        setup(mean, seed);
    }

    public double nextDouble() {
        return (double) _pdist.sample();
    }

}