/*
* 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.solr.util.hll;
import org.apache.lucene.util.LuceneTestCase;
import org.junit.Test;
/**
* Tests {@link HLLUtil} static methods.
*/
public class HLLUtilTest extends LuceneTestCase {
/**
* Tests that {@link HLLUtil#largeEstimatorCutoff(int, int)} is the same
* as a trivial implementation.
*/
@Test
public void largeEstimatorCutoffTest() {
for(int log2m=HLL.MINIMUM_LOG2M_PARAM; log2m<=HLL.MAXIMUM_LOG2M_PARAM; log2m++) {
for(int regWidth=HLL.MINIMUM_REGWIDTH_PARAM; regWidth<=HLL.MINIMUM_REGWIDTH_PARAM; regWidth++) {
final double cutoff = HLLUtil.largeEstimatorCutoff(log2m, regWidth);
// See blog post (http://research.neustar.biz/2013/01/24/hyperloglog-googles-take-on-engineering-hll/)
// and original paper (Fig. 3) for information on 2^L and
// "large range correction" cutoff.
final double expected = Math.pow(2, Math.pow(2, regWidth) - 2 + log2m) / 30.0;
assertEquals(cutoff, expected, 0.0001);
}
}
}
}