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