| /* |
| * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * @test |
| * @bug 8046516 |
| * @summary Segmentation fault in JVM (easily reproducible) |
| * @run main/othervm -XX:-TieredCompilation -Xbatch TestLogSum |
| * @author jackkamm@gmail.com |
| */ |
| |
| import java.util.Arrays; |
| import java.util.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| public class TestLogSum { |
| public static void main(String[] args) { |
| double sum; |
| |
| for (int i = 0; i < 6; i++) { |
| for (int n = 2; n < 30; n++) { |
| for (int j = 1; j <= n; j++) { |
| for (int k = 1; k <= j; k++) { |
| // System.out.println(computeSum(k, j)); |
| sum = computeSum(k, j); |
| } |
| } |
| } |
| } |
| } |
| |
| private static Map<List<Integer>, Double> cache = new HashMap<List<Integer>, Double>(); |
| public static double computeSum(int x, int y) { |
| List<Integer> key = Arrays.asList(new Integer[] {x, y}); |
| |
| if (!cache.containsKey(key)) { |
| |
| // explicitly creating/updating a double[] array, instead of using the LogSumArray wrapper object, will prevent the error |
| LogSumArray toReturn = new LogSumArray(x); |
| |
| // changing loop indices will prevent the error |
| // in particular, for(z=0; z<x-1; z++), and then using z+1 in place of z, will not produce error |
| for (int z = 1; z < x+1; z++) { |
| double logSummand = Math.log(z + x + y); |
| toReturn.addLogSummand(logSummand); |
| } |
| |
| // returning the value here without cacheing it will prevent the segfault |
| cache.put(key, toReturn.retrieveLogSum()); |
| } |
| return cache.get(key); |
| } |
| |
| /* |
| * Given a bunch of logarithms log(X),log(Y),log(Z),... |
| * This class is used to compute the log of the sum, log(X+Y+Z+...) |
| */ |
| private static class LogSumArray { |
| private double[] logSummandArray; |
| private int currSize; |
| |
| private double maxLogSummand; |
| |
| public LogSumArray(int maxEntries) { |
| this.logSummandArray = new double[maxEntries]; |
| |
| this.currSize = 0; |
| this.maxLogSummand = Double.NEGATIVE_INFINITY; |
| } |
| |
| public void addLogSummand(double logSummand) { |
| logSummandArray[currSize] = logSummand; |
| currSize++; |
| // removing this line will prevent the error |
| maxLogSummand = Math.max(maxLogSummand, logSummand); |
| } |
| |
| public double retrieveLogSum() { |
| if (maxLogSummand == Double.NEGATIVE_INFINITY) return Double.NEGATIVE_INFINITY; |
| |
| assert currSize <= logSummandArray.length; |
| |
| double factorSum = 0; |
| for (int i = 0; i < currSize; i++) { |
| factorSum += Math.exp(logSummandArray[i] - maxLogSummand); |
| } |
| |
| return Math.log(factorSum) + maxLogSummand; |
| } |
| } |
| } |