/**
* Licensed to Cloudera, Inc. under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Cloudera, Inc. 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 com.cloudera.util;
import java.util.List;
import org.junit.Assert;
import org.junit.Test;
/**
* Reservoir sampling extracts a certain number of samples from a set with
* uniform probability without knowing how many elements are in the total set.
*/
public class TestReservoirSampler {
@Test
public void testReserviorSampler() {
Histogram<Integer> h = new Histogram<Integer>();
for (int i = 0; i < 10000; i++) {
ReservoirSampler<Integer> rs = new ReservoirSampler<Integer>(10, i);
for (int j = 0; j < 100; j++) {
rs.onNext(j);
}
rs.onCompleted(true);
List<Integer> l = rs.sample();
for (Integer k : l) {
h.increment(k);
}
}
System.out.println(h);
for (int i = 0; i < 100; i++) {
int j = h.get(i);
// TODO (jon) it should be somewhere around 1000 hits per slot, but I'll
// approximate with these values for now. There is a formula somewhere for
// a more reasonable statistical bounds.
Assert.assertTrue(j < 1150 && j > 850);
}
}
}