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