// ============================================================================
// Copyright 2006-2012 Daniel W. Dyer
//
// 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 org.uncommons.maths.random;
import org.testng.annotations.Test;
import org.uncommons.maths.Maths;
import org.uncommons.maths.number.NumberGenerator;
import org.uncommons.maths.statistics.DataSet;
/**
* Unit test for the uniform integer number generator.
* @author Daniel Dyer
*/
public class DiscreteUniformGeneratorTest
{
/**
* Check that the observed mean and standard deviation are consistent
* with the specified distribution parameters.
*/
@Test(groups = "non-deterministic")
public void testDistribution()
{
final int min = 150;
final int max = 500;
final int range = max - min;
final double expectedMean = (range / 2) + min;
// Expected standard deviation for a uniformly distributed population of values in the range 0..n
// approaches n/sqrt(12).
final double standardDeviation = range / Math.sqrt(12);
NumberGenerator<Integer> generator = new DiscreteUniformGenerator(min,
max,
new MersenneTwisterRNG());
final int iterations = 10000;
DataSet data = new DataSet(iterations);
for (int i = 0; i < iterations; i++)
{
int value = generator.nextValue();
assert value >= min && value <= max : "Value out-of-range: " + value;
data.addValue(value);
}
assert Maths.approxEquals(data.getArithmeticMean(), expectedMean, 0.02)
: "Observed mean outside acceptable range: " + data.getArithmeticMean();
assert Maths.approxEquals(data.getSampleStandardDeviation(), standardDeviation, 0.02)
: "Observed standard deviation outside acceptable range: " + data.getSampleStandardDeviation();
// Expected median is the same as expected mean.
assert Maths.approxEquals(data.getMedian(), expectedMean, 0.02)
: "Observed mean outside acceptable range: " + data.getMedian();
}
}