diff options
author | brutisso <none@none> | 2011-06-28 14:23:27 +0200 |
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committer | brutisso <none@none> | 2011-06-28 14:23:27 +0200 |
commit | ed09d920ae29512ed5e3983476ea13d98aa2a635 (patch) | |
tree | 52d6fb7de60194230ebb1bfe1caac7f664cfd112 /src/share/vm/utilities/quickSort.hpp | |
parent | aff84d43a65dba4b02c71c5cf0cfaf549c2d63dd (diff) |
7016112: CMS: crash during promotion testing
Summary: Also reviewed by mikael.gerdin@oracle.com; stdlib:qsort() does byte-by-byte swapping on Windows. This leads to pointer shearing. Fix is to implement a quicksort that does full pointer updates.
Reviewed-by: never, coleenp, ysr
Diffstat (limited to 'src/share/vm/utilities/quickSort.hpp')
-rw-r--r-- | src/share/vm/utilities/quickSort.hpp | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/src/share/vm/utilities/quickSort.hpp b/src/share/vm/utilities/quickSort.hpp new file mode 100644 index 000000000..17eaf4693 --- /dev/null +++ b/src/share/vm/utilities/quickSort.hpp @@ -0,0 +1,138 @@ +/* + * Copyright (c) 2011, 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. + * + */ + +#ifndef SHARE_VM_UTILITIES_QUICKSORT_HPP +#define SHARE_VM_UTILITIES_QUICKSORT_HPP + +#include "memory/allocation.hpp" +#include "runtime/globals.hpp" +#include "utilities/debug.hpp" + +class QuickSort : AllStatic { + + private: + template<class T> + static void swap(T* array, int x, int y) { + T tmp = array[x]; + array[x] = array[y]; + array[y] = tmp; + } + + // As pivot we use the median of the first, last and middle elements. + // We swap in these three values at the right place in the array. This + // means that this method not only returns the index of the pivot + // element. It also alters the array so that: + // array[first] <= array[middle] <= array[last] + // A side effect of this is that arrays of length <= 3 are sorted. + template<class T, class C> + static int find_pivot(T* array, int length, C comparator) { + assert(length > 1, "length of array must be > 0"); + + int middle_index = length / 2; + int last_index = length - 1; + + if (comparator(array[0], array[middle_index]) == 1) { + swap(array, 0, middle_index); + } + if (comparator(array[0], array[last_index]) == 1) { + swap(array, 0, last_index); + } + if (comparator(array[middle_index], array[last_index]) == 1) { + swap(array, middle_index, last_index); + } + // Now the value in the middle of the array is the median + // of the fist, last and middle values. Use this as pivot. + return middle_index; + } + + template<class T, class C, bool idempotent> + static int partition(T* array, int pivot, int length, C comparator) { + int left_index = -1; + int right_index = length; + T pivot_val = array[pivot]; + + while (true) { + do { + left_index++; + } while (comparator(array[left_index], pivot_val) == -1); + do { + right_index--; + } while (comparator(array[right_index], pivot_val) == 1); + + if (left_index < right_index) { + if (!idempotent || comparator(array[left_index], array[right_index]) != 0) { + swap(array, left_index, right_index); + } + } else { + return right_index; + } + } + + ShouldNotReachHere(); + return 0; + } + + template<class T, class C, bool idempotent> + static void inner_sort(T* array, int length, C comparator) { + if (length < 2) { + return; + } + int pivot = find_pivot(array, length, comparator); + if (length < 4) { + // arrays up to length 3 will be sorted after finding the pivot + return; + } + int split = partition<T, C, idempotent>(array, pivot, length, comparator); + int first_part_length = split + 1; + inner_sort<T, C, idempotent>(array, first_part_length, comparator); + inner_sort<T, C, idempotent>(&array[first_part_length], length - first_part_length, comparator); + } + + public: + // The idempotent parameter prevents the sort from + // reordering a previous valid sort by not swapping + // fields that compare as equal. This requires extra + // calls to the comparator, so the performance + // impact depends on the comparator. + template<class T, class C> + static void sort(T* array, int length, C comparator, bool idempotent) { + // Switch "idempotent" from function paramter to template parameter + if (idempotent) { + inner_sort<T, C, true>(array, length, comparator); + } else { + inner_sort<T, C, false>(array, length, comparator); + } + } + + // for unit testing +#ifndef PRODUCT + static void print_array(const char* prefix, int* array, int length); + static bool compare_arrays(int* actual, int* expected, int length); + template <class C> static bool sort_and_compare(int* arrayToSort, int* expectedResult, int length, C comparator, bool idempotent = false); + static bool test_quick_sort(); +#endif +}; + + +#endif //SHARE_VM_UTILITIES_QUICKSORT_HPP |