Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264493AbUDZKgN (ORCPT ); Mon, 26 Apr 2004 06:36:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264526AbUDZKeE (ORCPT ); Mon, 26 Apr 2004 06:34:04 -0400 Received: from ns.suse.de ([195.135.220.2]:61653 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S264493AbUDZK2w (ORCPT ); Mon, 26 Apr 2004 06:28:52 -0400 Subject: [PATCH 8/11] qsort From: Andreas Gruenbacher To: Andrew Morton , lkml Content-Type: text/plain Organization: SUSE Labs, SUSE LINUX AG Message-Id: <1082975201.3295.78.camel@winden.suse.de> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.4 Date: Mon, 26 Apr 2004 12:28:48 +0200 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10633 Lines: 305 Add qsort This is qsort from glibc. We need it in nfsacl. Andreas Gruenbacher , SUSE Labs Index: linux-2.6.6-rc2/include/linux/kernel.h =================================================================== --- linux-2.6.6-rc2.orig/include/linux/kernel.h +++ linux-2.6.6-rc2/include/linux/kernel.h @@ -80,6 +80,8 @@ extern int sscanf(const char *, const ch __attribute__ ((format (scanf,2,3))); extern int vsscanf(const char *, const char *, va_list); +extern void qsort(void *, size_t, size_t, int (*)(const void *,const void *)); + extern int get_option(char **str, int *pint); extern char *get_options(const char *str, int nints, int *ints); extern unsigned long long memparse(char *ptr, char **retptr); Index: linux-2.6.6-rc2/lib/Kconfig =================================================================== --- linux-2.6.6-rc2.orig/lib/Kconfig +++ linux-2.6.6-rc2/lib/Kconfig @@ -12,6 +12,9 @@ config CRC32 kernel tree does. Such modules that use library CRC32 functions require M here. +config QSORT + bool "Quick Sort" + # # compression support is select'ed if needed # Index: linux-2.6.6-rc2/lib/Makefile =================================================================== --- linux-2.6.6-rc2.orig/lib/Makefile +++ linux-2.6.6-rc2/lib/Makefile @@ -19,6 +19,7 @@ ifneq ($(CONFIG_HAVE_DEC_LOCK),y) endif obj-$(CONFIG_CRC32) += crc32.o +obj-$(CONFIG_QSORT) += qsort.o obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/ obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/ Index: linux-2.6.6-rc2/lib/qsort.c =================================================================== --- linux-2.6.6-rc2.orig/lib/qsort.c +++ linux-2.6.6-rc2/lib/qsort.c @@ -0,0 +1,249 @@ +/* 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); - 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/