Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261962AbVAaHp2 (ORCPT ); Mon, 31 Jan 2005 02:45:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261967AbVAaHmw (ORCPT ); Mon, 31 Jan 2005 02:42:52 -0500 Received: from waste.org ([216.27.176.166]:60140 "EHLO waste.org") by vger.kernel.org with ESMTP id S261953AbVAaHfC (ORCPT ); Mon, 31 Jan 2005 02:35:02 -0500 Date: Mon, 31 Jan 2005 01:35:00 -0600 From: Matt Mackall To: Andrew Morton X-PatchBomber: http://selenic.com/scripts/mailpatches Cc: linux-kernel@vger.kernel.org In-Reply-To: <4.416337461@selenic.com> Message-Id: <5.416337461@selenic.com> Subject: [PATCH 4/8] lib/sort: Kill qsort() Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10107 Lines: 289 Remove qsort() before anyone gets too attached to it. Signed-off-by: Matt Mackall Index: mm2/lib/qsort.c =================================================================== --- mm2.orig/lib/qsort.c 2005-01-30 20:33:19.000000000 -0800 +++ /dev/null 1970-01-01 00:00:00.000000000 +0000 @@ -1,249 +0,0 @@ -/* Copyright (C) 1991, 1992, 1996, 1997, 1999 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Written by Douglas C. Schmidt (schmidt@ics.uci.edu). - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library 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 - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, write to the Free - Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA - 02111-1307 USA. */ - -/* If you consider tuning this algorithm, you should consult first: - Engineering a sort function; Jon Bentley and M. Douglas McIlroy; - Software - Practice and Experience; Vol. 23 (11), 1249-1265, 1993. */ - -# include -# include -# include - -MODULE_LICENSE("GPL"); - -/* Byte-wise swap two items of size SIZE. */ -#define SWAP(a, b, size) \ - do \ - { \ - register size_t __size = (size); \ - register char *__a = (a), *__b = (b); \ - do \ - { \ - char __tmp = *__a; \ - *__a++ = *__b; \ - *__b++ = __tmp; \ - } while (--__size > 0); \ - } while (0) - -/* Discontinue quicksort algorithm when partition gets below this size. - This particular magic number was chosen to work best on a Sun 4/260. */ -#define MAX_THRESH 4 - -/* Stack node declarations used to store unfulfilled partition obligations. */ -typedef struct - { - char *lo; - char *hi; - } stack_node; - -/* The next 5 #defines implement a very fast in-line stack abstraction. */ -/* The stack needs log (total_elements) entries (we could even subtract - log(MAX_THRESH)). Since total_elements has type size_t, we get as - upper bound for log (total_elements): - bits per byte (CHAR_BIT) * sizeof(size_t). */ -#define CHAR_BIT 8 -#define STACK_SIZE (CHAR_BIT * sizeof(size_t)) -#define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top)) -#define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi))) -#define STACK_NOT_EMPTY (stack < top) - - -/* Order size using quicksort. This implementation incorporates - four optimizations discussed in Sedgewick: - - 1. Non-recursive, using an explicit stack of pointer that store the - next array partition to sort. To save time, this maximum amount - of space required to store an array of SIZE_MAX is allocated on the - stack. Assuming a 32-bit (64 bit) integer for size_t, this needs - only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes). - Pretty cheap, actually. - - 2. Chose the pivot element using a median-of-three decision tree. - This reduces the probability of selecting a bad pivot value and - eliminates certain extraneous comparisons. - - 3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving - insertion sort to order the MAX_THRESH items within each partition. - This is a big win, since insertion sort is faster for small, mostly - sorted array segments. - - 4. The larger of the two sub-partitions is always pushed onto the - stack first, with the algorithm then concentrating on the - smaller partition. This *guarantees* no more than log (total_elems) - stack size is needed (actually O(1) in this case)! */ - -void -qsort(void *const pbase, size_t total_elems, size_t size, - int(*cmp)(const void *,const void *)) -{ - register char *base_ptr = (char *) pbase; - - const size_t max_thresh = MAX_THRESH * size; - - if (total_elems == 0) - /* Avoid lossage with unsigned arithmetic below. */ - return; - - if (total_elems > MAX_THRESH) - { - char *lo = base_ptr; - char *hi = &lo[size * (total_elems - 1)]; - stack_node stack[STACK_SIZE]; - stack_node *top = stack + 1; - - while (STACK_NOT_EMPTY) - { - char *left_ptr; - char *right_ptr; - - /* Select median value from among LO, MID, and HI. Rearrange - LO and HI so the three values are sorted. This lowers the - probability of picking a pathological pivot value and - skips a comparison for both the LEFT_PTR and RIGHT_PTR in - the while loops. */ - - char *mid = lo + size * ((hi - lo) / size >> 1); - - if ((*cmp) ((void *) mid, (void *) lo) < 0) - SWAP (mid, lo, size); - if ((*cmp) ((void *) hi, (void *) mid) < 0) - SWAP (mid, hi, size); - else - goto jump_over; - if ((*cmp) ((void *) mid, (void *) lo) < 0) - SWAP (mid, lo, size); - jump_over:; - - left_ptr = lo + size; - right_ptr = hi - size; - - /* Here's the famous ``collapse the walls'' section of quicksort. - Gotta like those tight inner loops! They are the main reason - that this algorithm runs much faster than others. */ - do - { - while ((*cmp) ((void *) left_ptr, (void *) mid) < 0) - left_ptr += size; - - while ((*cmp) ((void *) mid, (void *) right_ptr) < 0) - right_ptr -= size; - - if (left_ptr < right_ptr) - { - SWAP (left_ptr, right_ptr, size); - if (mid == left_ptr) - mid = right_ptr; - else if (mid == right_ptr) - mid = left_ptr; - left_ptr += size; - right_ptr -= size; - } - else if (left_ptr == right_ptr) - { - left_ptr += size; - right_ptr -= size; - break; - } - } - while (left_ptr <= right_ptr); - - /* Set up pointers for next iteration. First determine whether - left and right partitions are below the threshold size. If so, - ignore one or both. Otherwise, push the larger partition's - bounds on the stack and continue sorting the smaller one. */ - - if ((size_t) (right_ptr - lo) <= max_thresh) - { - if ((size_t) (hi - left_ptr) <= max_thresh) - /* Ignore both small partitions. */ - POP (lo, hi); - else - /* Ignore small left partition. */ - lo = left_ptr; - } - else if ((size_t) (hi - left_ptr) <= max_thresh) - /* Ignore small right partition. */ - hi = right_ptr; - else if ((right_ptr - lo) > (hi - left_ptr)) - { - /* Push larger left partition indices. */ - PUSH (lo, right_ptr); - lo = left_ptr; - } - else - { - /* Push larger right partition indices. */ - PUSH (left_ptr, hi); - hi = right_ptr; - } - } - } - - /* Once the BASE_PTR array is partially sorted by quicksort the rest - is completely sorted using insertion sort, since this is efficient - for partitions below MAX_THRESH size. BASE_PTR points to the beginning - of the array to sort, and END_PTR points at the very last element in - the array (*not* one beyond it!). */ - - { - char *end_ptr = &base_ptr[size * (total_elems - 1)]; - char *tmp_ptr = base_ptr; - char *thresh = min(end_ptr, base_ptr + max_thresh); - register char *run_ptr; - - /* Find smallest element in first threshold and place it at the - array's beginning. This is the smallest array element, - and the operation speeds up insertion sort's inner loop. */ - - for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size) - if ((*cmp) ((void *) run_ptr, (void *) tmp_ptr) < 0) - tmp_ptr = run_ptr; - - if (tmp_ptr != base_ptr) - SWAP (tmp_ptr, base_ptr, size); - - /* Insertion sort, running from left-hand-side up to right-hand-side. */ - - run_ptr = base_ptr + size; - while ((run_ptr += size) <= end_ptr) - { - tmp_ptr = run_ptr - size; - while ((*cmp) ((void *) run_ptr, (void *) tmp_ptr) < 0) - tmp_ptr -= size; - - tmp_ptr += size; - if (tmp_ptr != run_ptr) - { - char *trav; - - trav = run_ptr + size; - while (--trav >= run_ptr) - { - char c = *trav; - char *hi, *lo; - - for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo) - *hi = *lo; - *hi = c; - } - } - } - } -} -EXPORT_SYMBOL(qsort); Index: mm2/lib/Kconfig =================================================================== --- mm2.orig/lib/Kconfig 2005-01-30 20:33:19.000000000 -0800 +++ mm2/lib/Kconfig 2005-01-30 20:36:12.000000000 -0800 @@ -30,9 +30,6 @@ require M here. See Castagnoli93. Module will be libcrc32c. -config QSORT - bool "Quick Sort" - # # compression support is select'ed if needed # Index: mm2/lib/Makefile =================================================================== --- mm2.orig/lib/Makefile 2005-01-30 20:33:19.000000000 -0800 +++ mm2/lib/Makefile 2005-01-30 20:36:12.000000000 -0800 @@ -26,7 +26,6 @@ obj-$(CONFIG_CRC32) += crc32.o obj-$(CONFIG_LIBCRC32C) += libcrc32c.o obj-$(CONFIG_GENERIC_IOMAP) += iomap.o -obj-$(CONFIG_QSORT) += qsort.o obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/ obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/