Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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;

       }

    }

 }