1 /* 2 * Copyright (c) 2014, 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 /* 25 * @test 26 * @bug 8046516 27 * @summary Segmentation fault in JVM (easily reproducible) 28 * 29 * @run main/othervm -XX:-TieredCompilation -Xbatch compiler.loopopts.TestLogSum 30 * @author jackkamm@gmail.com 31 */ 32 33 package compiler.loopopts; 34 35 import java.util.Arrays; 36 import java.util.HashMap; 37 import java.util.List; 38 import java.util.Map; 39 40 public class TestLogSum { 41 public static void main(String[] args) { 42 double sum; 43 44 for (int i = 0; i < 6; i++) { 45 for (int n = 2; n < 30; n++) { 46 for (int j = 1; j <= n; j++) { 47 for (int k = 1; k <= j; k++) { 48 // System.out.println(computeSum(k, j)); 49 sum = computeSum(k, j); 50 } 51 } 52 } 53 } 54 } 55 56 private static Map<List<Integer>, Double> cache = new HashMap<List<Integer>, Double>(); 57 public static double computeSum(int x, int y) { 58 List<Integer> key = Arrays.asList(new Integer[] {x, y}); 59 60 if (!cache.containsKey(key)) { 61 62 // explicitly creating/updating a double[] array, instead of using the LogSumArray wrapper object, will prevent the error 63 LogSumArray toReturn = new LogSumArray(x); 64 65 // changing loop indices will prevent the error 66 // in particular, for(z=0; z<x-1; z++), and then using z+1 in place of z, will not produce error 67 for (int z = 1; z < x+1; z++) { 68 double logSummand = Math.log(z + x + y); 69 toReturn.addLogSummand(logSummand); 70 } 71 72 // returning the value here without cacheing it will prevent the segfault 73 cache.put(key, toReturn.retrieveLogSum()); 74 } 75 return cache.get(key); 76 } 77 78 /* 79 * Given a bunch of logarithms log(X),log(Y),log(Z),... 80 * This class is used to compute the log of the sum, log(X+Y+Z+...) 81 */ 82 private static class LogSumArray { 83 private double[] logSummandArray; 84 private int currSize; 85 86 private double maxLogSummand; 87 88 public LogSumArray(int maxEntries) { 89 this.logSummandArray = new double[maxEntries]; 90 91 this.currSize = 0; 92 this.maxLogSummand = Double.NEGATIVE_INFINITY; 93 } 94 95 public void addLogSummand(double logSummand) { 96 logSummandArray[currSize] = logSummand; 97 currSize++; 98 // removing this line will prevent the error 99 maxLogSummand = Math.max(maxLogSummand, logSummand); 100 } 101 102 public double retrieveLogSum() { 103 if (maxLogSummand == Double.NEGATIVE_INFINITY) return Double.NEGATIVE_INFINITY; 104 105 assert currSize <= logSummandArray.length; 106 107 double factorSum = 0; 108 for (int i = 0; i < currSize; i++) { 109 factorSum += Math.exp(logSummandArray[i] - maxLogSummand); 110 } 111 112 return Math.log(factorSum) + maxLogSummand; 113 } 114 } 115 }