| /* |
| * 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.flink.api.java.summarize.aggregation; |
| |
| import org.junit.Assert; |
| import org.junit.Test; |
| |
| /** |
| * Tests for {@link CompensatedSum}. |
| */ |
| public class CompensatedSumTest { |
| |
| /** |
| * When adding a series of numbers the order of the numbers should not impact the results. |
| * |
| * <p>This test shows that a naive summation comes up with a different result than Kahan |
| * Summation when you start with either a smaller or larger number in some cases and |
| * helps prove our Kahan Summation is working. |
| */ |
| @Test |
| public void testAdd1() throws Exception { |
| final CompensatedSum smallSum = new CompensatedSum(0.001, 0.0); |
| final CompensatedSum largeSum = new CompensatedSum(1000, 0.0); |
| |
| CompensatedSum compensatedResult1 = smallSum; |
| CompensatedSum compensatedResult2 = largeSum; |
| double naiveResult1 = smallSum.value(); |
| double naiveResult2 = largeSum.value(); |
| |
| for (int i = 0; i < 10; i++) { |
| compensatedResult1 = compensatedResult1.add(smallSum); |
| compensatedResult2 = compensatedResult2.add(smallSum); |
| naiveResult1 += smallSum.value(); |
| naiveResult2 += smallSum.value(); |
| } |
| |
| compensatedResult1 = compensatedResult1.add(largeSum); |
| compensatedResult2 = compensatedResult2.add(smallSum); |
| naiveResult1 += largeSum.value(); |
| naiveResult2 += smallSum.value(); |
| |
| // Kahan summation gave the same result no matter what order we added |
| Assert.assertEquals(1000.011, compensatedResult1.value(), 0.0); |
| Assert.assertEquals(1000.011, compensatedResult2.value(), 0.0); |
| |
| // naive addition gave a small floating point error |
| Assert.assertEquals(1000.011, naiveResult1, 0.0); |
| Assert.assertEquals(1000.0109999999997, naiveResult2, 0.0); |
| |
| Assert.assertEquals(compensatedResult1.value(), compensatedResult2.value(), 0.0); |
| Assert.assertEquals(naiveResult1, naiveResult2, 0.0001); |
| Assert.assertNotEquals(naiveResult1, naiveResult2, 0.0); |
| } |
| |
| @Test |
| public void testDelta() throws Exception { |
| CompensatedSum compensatedResult1 = new CompensatedSum(0.001, 0.0); |
| for (int i = 0; i < 10; i++) { |
| compensatedResult1 = compensatedResult1.add(0.001); |
| } |
| Assert.assertEquals(0.011, compensatedResult1.value(), 0.0); |
| Assert.assertEquals(new Double("8.673617379884035E-19"), compensatedResult1.delta(), 0.0); |
| } |
| |
| } |