bigtop-master/bigtop-data-generators/bigtop-samplers/src/main/java/org/apache/bigtop/datagenerators/samplers/samplers/BoundedMultiModalGaussianSampler.java
/**
 * 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.bigtop.datagenerators.samplers.samplers;

import java.util.List;
import java.util.Random;

import org.apache.bigtop.datagenerators.samplers.SeedFactory;
import org.apache.commons.lang3.tuple.Pair;

import com.google.common.collect.ImmutableList;

public class BoundedMultiModalGaussianSampler implements Sampler<Double>
{
	ImmutableList<Pair<Double, Double>> distributions;

	double min;
	double max;
	Random rng;

	public BoundedMultiModalGaussianSampler(List<Pair<Double, Double>> distributions, double min, double max, SeedFactory seedFactory)
	{
		rng = new Random(seedFactory.getNextSeed());
		this.distributions = ImmutableList.copyOf(distributions);

		this.min = min;
		this.max = max;
	}

	public Double sample()
	{
		while(true)
		{
			int idx = rng.nextInt(distributions.size());

			double mean = distributions.get(idx).getLeft();
			double std = distributions.get(idx).getRight();

			double value = mean + rng.nextGaussian() * std;

			if (value >= this.min && value <= this.max)
			{
				return value;
			}
		}
	}

}
