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 }