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Update.
2002-01-16 Roger Sayle <roger@eyesopen.com> * stdlib/msort.c (msort_with_tmp): Replace implementation with more efficient "Towers of Hanoi" mergesort. (hanoi_sort, hanoi_sort_int, hanoi_sort_long): New functions, for generic, sizeof(int) and sizeof(long) variants respectively. * manial/syslog.texi (openlog): Describe possible problems with first parameter. Patch by Christopher Allen Wing <wingc@engin.umich.edu>.
This commit is contained in:
Ulrich Drepper
406
stdlib/msort.c
406
stdlib/msort.c
@@ -1,7 +1,9 @@
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/* An alternative to qsort, with an identical interface.
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This file is part of the GNU C Library.
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Copyright (C) 1992, 1995-1997, 1999, 2000, 2001 Free Software Foundation, Inc.
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Written by Mike Haertel, September 1988.
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Copyright (C) 1992, 1995-1997, 1999, 2000, 2001, 2002
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Free Software Foundation, Inc.
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Original Implementation by Mike Haertel, September 1988.
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Towers of Hanoi Mergesort by Roger Sayle, January 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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@@ -19,70 +21,372 @@
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02111-1307 USA. */
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#include <alloca.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <memcopy.h>
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#include <errno.h>
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static void msort_with_tmp (void *b, size_t n, size_t s,
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__compar_fn_t cmp, char *t);
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static void
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msort_with_tmp (void *b, size_t n, size_t s, __compar_fn_t cmp,
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char *t)
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/* Check whether pointer P is aligned for access by type T. */
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#define TYPE_ALIGNED(P,T) (((char *) (P) - (char *) 0) % __alignof__ (T) == 0)
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static int hanoi_sort (char *b, size_t n, size_t s,
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__compar_fn_t cmp, char *t);
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static int hanoi_sort_int (int *b, size_t n,
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__compar_fn_t cmp, int *t);
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#if INT_MAX != LONG_MAX
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static int hanoi_sort_long (long int *b, size_t n,
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__compar_fn_t cmp, long int *t);
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#endif
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static void msort_with_tmp (void *b, size_t n, size_t s,
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__compar_fn_t cmp, void *t);
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/* This routine implements "Towers of Hanoi Mergesort". The algorithm
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sorts the n elements of size s pointed to by array b using comparison
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function cmp. The argument t points to a suitable temporary buffer.
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If the return value is zero, the sorted array is returned in b, and
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for non-zero return values the sorted array is returned in t. */
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static int
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hanoi_sort (char *b, size_t n, size_t s, __compar_fn_t cmp, char *t)
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{
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char *tmp;
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char *b1, *b2;
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size_t n1, n2;
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char *b1,*b2;
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char *t1,*t2;
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char *s1,*s2;
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size_t size;
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int result;
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char *ptr;
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if (n <= 1)
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return;
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return 0;
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n1 = n / 2;
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if (n == 2)
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{
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b2 = b + s;
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if ((*cmp) (b, b2) <= 0)
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return 0;
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memcpy (__mempcpy (t, b2, s), b, s);
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return 1;
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}
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n1 = n/2;
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n2 = n - n1;
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/* n1 < n2! */
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size = n1 * s;
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b1 = b;
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b2 = (char *) b + (n1 * s);
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b2 = b + size;
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msort_with_tmp (b1, n1, s, cmp, t);
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msort_with_tmp (b2, n2, s, cmp, t);
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t1 = t;
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t2 = t + size;
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tmp = t;
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if (s == OPSIZ && (b1 - (char *) 0) % OPSIZ == 0)
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/* We are operating on aligned words. Use direct word stores. */
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2) <= 0)
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{
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--n1;
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*((op_t *) tmp)++ = *((op_t *) b1)++;
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}
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else
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{
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--n2;
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*((op_t *) tmp)++ = *((op_t *) b2)++;
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}
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}
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/* Recursively call hanoi_sort to sort the two halves of the array.
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Depending upon the return values, determine the values s1 and s2
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the locations of the two sorted subarrays, ptr, the location to
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contain the sorted array and result, the return value for this
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function. Note that "ptr = result? t : b". */
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if (hanoi_sort (b1, n1, s, cmp, t1))
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{
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if (hanoi_sort (b2, n2, s, cmp, t2))
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = t2;
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}
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else
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = b2;
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}
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}
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else
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while (n1 > 0 && n2 > 0)
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{
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if ((*cmp) (b1, b2) <= 0)
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{
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tmp = (char *) __mempcpy (tmp, b1, s);
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b1 += s;
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--n1;
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}
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else
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{
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tmp = (char *) __mempcpy (tmp, b2, s);
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b2 += s;
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--n2;
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}
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}
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if (n1 > 0)
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memcpy (tmp, b1, n1 * s);
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memcpy (b, t, (n - n2) * s);
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{
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if (hanoi_sort (b2, n2, s, cmp, t2))
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = t2;
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}
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else
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = b2;
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}
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}
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/* Merge the two sorted arrays s1 and s2 of n1 and n2 elements
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respectively, placing the result in ptr. On entry, n1 > 0
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&& n2 > 0, and with each iteration either n1 or n2 is decreased
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until either reaches zero, and the loop terminates via return. */
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for (;;)
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{
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if ((*cmp) (s1, s2) <= 0)
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{
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ptr = (char *) __mempcpy (ptr, s1, s);
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s1 += s;
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--n1;
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if (n1 == 0)
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{
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if (ptr != s2)
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memcpy (ptr, s2, n2 * s);
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return result;
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}
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}
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else
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{
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ptr = (char *) __mempcpy (ptr, s2, s);
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s2 += s;
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--n2;
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if (n2 == 0)
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{
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memcpy (ptr, s1, n1 * s);
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return result;
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}
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}
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}
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}
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/* This routine is a variant of hanoi_sort that is optimized for the
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case where items to be sorted are the size of ints, and both b and
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t are suitably aligned. The parameter s in not needed as it is
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known to be sizeof(int). */
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static int
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hanoi_sort_int (int *b, size_t n, __compar_fn_t cmp, int *t)
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{
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size_t n1, n2;
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int *b1,*b2;
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int *t1,*t2;
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int *s1,*s2;
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int result;
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int *ptr;
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if (n <= 1)
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return 0;
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if (n == 2)
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{
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if ((*cmp) (b, b + 1) <= 0)
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return 0;
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t[0] = b[1];
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t[1] = b[0];
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return 1;
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}
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n1 = n/2;
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n2 = n - n1;
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/* n1 < n2! */
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b1 = b;
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b2 = b + n1;
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t1 = t;
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t2 = t + n1;
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/* Recursively call hanoi_sort_int to sort the two halves. */
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if (hanoi_sort_int (b1, n1, cmp, t1))
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{
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if (hanoi_sort_int (b2, n2, cmp, t2))
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = t2;
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}
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else
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = b2;
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}
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}
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else
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{
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if (hanoi_sort_int (b2, n2, cmp, t2))
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = t2;
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}
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else
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = b2;
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}
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}
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/* Merge n1 elements from s1 and n2 elements from s2 into ptr. */
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for (;;)
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{
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if ((*cmp) (s1, s2) <= 0)
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{
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*ptr++ = *s1++;
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--n1;
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if (n1 == 0)
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{
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if (ptr != s2)
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memcpy (ptr, s2, n2 * sizeof (int));
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return result;
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}
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}
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else
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{
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*ptr++ = *s2++;
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--n2;
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if (n2 == 0)
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{
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memcpy (ptr, s1, n1 * sizeof (int));
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return result;
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}
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}
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}
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}
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#if INT_MAX != LONG_MAX
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/* This routine is a variant of hanoi_sort that is optimized for the
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case where items to be sorted are the size of longs, and both b and
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t are suitably aligned. The parameter s in not needed as it is
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known to be sizeof(long). In case sizeof(int)== sizeof(long) we
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do not need this code since it would be the same as hanoi_sort_int. */
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static int
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hanoi_sort_long (long int *b, size_t n, __compar_fn_t cmp, long int *t)
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{
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size_t n1, n2;
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long int *b1,*b2;
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long int *t1,*t2;
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long int *s1,*s2;
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int result;
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long int *ptr;
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if (n <= 1)
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return 0;
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if (n == 2)
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{
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if ((*cmp) (b, b + 1) <= 0)
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return 0;
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t[0] = b[1];
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t[1] = b[0];
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return 1;
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}
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n1 = n/2;
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n2 = n - n1;
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/* n1 < n2! */
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b1 = b;
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b2 = b + n1;
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t1 = t;
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t2 = t + n1;
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/* Recursively call hanoi_sort_long to sort the two halves. */
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if (hanoi_sort_long (b1, n1, cmp, t1))
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{
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if (hanoi_sort_long (b2, n2, cmp, t2))
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = t2;
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}
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else
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{
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result = 0;
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ptr = b;
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s1 = t1;
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s2 = b2;
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}
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}
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else
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{
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if (hanoi_sort_long (b2, n2, cmp, t2))
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = t2;
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}
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else
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{
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result = 1;
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ptr = t;
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s1 = b1;
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s2 = b2;
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}
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}
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/* Merge n1 elements from s1 and n2 elements from s2 into ptr. */
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for (;;)
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{
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if ((*cmp) (s1, s2) <= 0)
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{
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*ptr++ = *s1++;
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--n1;
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if (n1 == 0)
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{
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if (ptr != s2)
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memcpy (ptr, s2, n2 * sizeof (long));
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return result;
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}
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}
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else
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{
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*ptr++ = *s2++;
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--n2;
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if (n2 == 0)
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{
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memcpy (ptr, s1, n1 * sizeof (long));
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return result;
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}
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}
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}
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}
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#endif
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/* This routine preserves the original interface to msort_with_tmp and
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determines which variant of hanoi_sort to call, based upon item size
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and alignment. */
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static void
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msort_with_tmp (void *b, size_t n, size_t s, __compar_fn_t cmp, void *t)
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{
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const size_t size = n * s;
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if (s == sizeof (int) && TYPE_ALIGNED (b, int))
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{
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if (hanoi_sort_int (b, n, cmp, t))
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memcpy (b, t, size);
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}
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#if INT_MAX != LONG_MAX
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else if (s == sizeof (long int) && TYPE_ALIGNED (b, long int))
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{
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if (hanoi_sort_long (b, n, cmp, t))
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memcpy (b, t, size);
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}
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#endif
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else
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{
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/* Call the generic implementation. */
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if (hanoi_sort (b, n, s, cmp, t))
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memcpy (b, t, size);
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}
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}
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void
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@@ -93,7 +397,7 @@ qsort (void *b, size_t n, size_t s, __compar_fn_t cmp)
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if (size < 1024)
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{
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void *buf = __alloca (size);
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/* The temporary array is small, so put it on the stack. */
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msort_with_tmp (b, n, s, cmp, buf);
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}
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@@ -130,7 +434,7 @@ qsort (void *b, size_t n, size_t s, __compar_fn_t cmp)
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measured in bytes. */
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/* If the memory requirements are too high don't allocate memory. */
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if (size / pagesize > phys_pages)
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if ((long int) (size / pagesize) > phys_pages)
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_quicksort (b, n, s, cmp);
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else
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{
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