1 /* 2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 import java.util.*; 25 import java.util.stream.*; 26 27 /* 28 * @test 29 * @bug 8006572 30 */ 31 public class TestDoubleSumAverage { 32 public static void main(String... args) { 33 int failures = 0; 34 35 double base = 1.0; 36 double increment = Math.ulp(base)/2.0; 37 int count = 1_000_001; 38 /* 39 * The exact sum of the test stream is 1 + 1e6*ulp(1.0) but a 40 * naive summation algorithm will return 1.0 since (1.0 + 41 * ulp(1.0)/2) will round to 1.0 again. 42 */ 43 DoubleSummaryStatistics stats = 44 testStream(base, increment, count).collect(DoubleSummaryStatistics::new, 45 DoubleSummaryStatistics::accept, 46 DoubleSummaryStatistics::combine); 47 48 double expectedSum = base + (increment * (count - 1)); 49 double expectedAvg = expectedSum / count; 50 51 failures += compareUlpDifference(expectedSum, stats.getSum(), 3); 52 failures += compareUlpDifference(expectedAvg, stats.getAverage(), 3); 53 54 failures += compareUlpDifference(expectedSum, testStream(base, increment, count).sum(), 3); 55 failures += compareUlpDifference(expectedAvg, testStream(base, increment, count).average().getAsDouble(), 3); 56 57 double collectorSum = testBoxedStream(base, increment, count). 58 collect(Collectors.summingDouble(d -> d)); 59 failures += compareUlpDifference(expectedSum, collectorSum, 3); 60 61 double collectorAvg = testBoxedStream(base, increment, count). 62 collect(Collectors.averagingDouble(d -> d)); 63 failures += compareUlpDifference(expectedAvg, collectorAvg, 3); 64 65 if (failures > 0) { 66 throw new RuntimeException("Found " + failures + " numerical failures."); 67 } 68 } 69 70 private static DoubleStream testStream(double base, double increment, int count) { 71 return StreamSupport. 72 doubleStream(Spliterators.spliteratorUnknownSize(new TestDoubleIterator(base, 73 increment, 74 count), 75 Spliterator.IMMUTABLE | 76 Spliterator.NONNULL), 77 false); 78 } 79 80 private static Stream<Double> testBoxedStream(double base, double increment, int count) { 81 TestDoubleIterator tdi = new TestDoubleIterator(base, increment, count); 82 Double[] tmp = new Double[count]; 83 int i = 0; 84 while(tdi.hasNext()) { 85 tmp[i] = tdi.next(); 86 i++; 87 } 88 return Stream.of(tmp); 89 } 90 91 private static int compareUlpDifference(double expected, double computed, double threshold) { 92 double ulpDifference = Math.abs(expected - computed) / Math.ulp(expected); 93 94 if (ulpDifference > threshold) { 95 System.err.printf("Numerical summation error too large, %g ulps rather than %g.%n", 96 ulpDifference, threshold); 97 return 1; 98 } else 99 return 0; 100 } 101 102 static class TestDoubleIterator implements PrimitiveIterator.OfDouble { 103 private double base; 104 private double subsequent; 105 private long count; 106 private long iteration = 0; 107 108 /** 109 * Construct a {@code TestDoubleStream} of {@code count} 110 * elements whose first value is {@code base} and whose 111 * following values are all {@code subsequent}. 112 */ 113 TestDoubleIterator(double base, double subsequent, long count) { 114 this.base = base; 115 this.subsequent = subsequent; 116 this.count = count; 117 } 118 119 @Override 120 public boolean hasNext() { 121 return (iteration < count); 122 } 123 124 @Override 125 public double nextDouble() { 126 if (iteration >= count) 127 throw new NoSuchElementException(); 128 else { 129 iteration++; 130 return (iteration == 1) ? base : subsequent; 131 } 132 } 133 } 134 }