/*
* 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.mahout.math.random;
import org.apache.commons.math3.distribution.IntegerDistribution;
import org.apache.commons.math3.distribution.PoissonDistribution;
import org.apache.mahout.common.RandomUtils;
import org.apache.mahout.math.MahoutTestCase;
import org.junit.Before;
import org.junit.Test;
public final class PoissonSamplerTest extends MahoutTestCase {
@Override
@Before
public void setUp() {
RandomUtils.useTestSeed();
}
@Test
public void testBasics() {
for (double alpha : new double[]{0.1, 1, 10, 100}) {
checkDistribution(new PoissonSampler(alpha), alpha);
}
}
private static void checkDistribution(Sampler<Double> pd, double alpha) {
int[] count = new int[(int) Math.max(10, 5 * alpha)];
for (int i = 0; i < 10000; i++) {
count[pd.sample().intValue()]++;
}
IntegerDistribution ref = new PoissonDistribution(RandomUtils.getRandom().getRandomGenerator(),
alpha,
PoissonDistribution.DEFAULT_EPSILON,
PoissonDistribution.DEFAULT_MAX_ITERATIONS);
for (int i = 0; i < count.length; i++) {
assertEquals(ref.probability(i), count[i] / 10000.0, 2.0e-2);
}
}
}