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