/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.sysml.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;
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 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();
}
}