Make g_qsort_with_data stable, based on glibc msort

We need a stable sort, and we might as well always use it rather
than have multiple sort versions. This picks up the glibc
merge sort implementation which it uses by default for qsort,
except we don't fall back to non-stable quicksort in some cases
like glibc

https://bugzilla.gnome.org/show_bug.cgi?id=672095
This commit is contained in:
Alexander Larsson 2012-03-14 21:17:23 +01:00
parent 8da9478920
commit 839957f275
3 changed files with 325 additions and 249 deletions

View File

@ -3411,6 +3411,37 @@ if test x$glib_win32_static_compilation = xyes; then
fi
])
# Redo enough to get guint32 and guint64 for the alignment checks below
case 4 in
$ac_cv_sizeof_short)
gint32=short
;;
$ac_cv_sizeof_int)
gint32=int
;;
$ac_cv_sizeof_long)
gint32=long
;;
esac
case 8 in
$ac_cv_sizeof_int)
gint64=int
;;
$ac_cv_sizeof_long)
gint64=long
;;
$ac_cv_sizeof_long_long)
gint64='long long'
;;
$ac_cv_sizeof___int64)
gint64='__int64'
;;
esac
AC_CHECK_ALIGNOF([guint32], [typedef unsigned $gint32 guint32;])
AC_CHECK_ALIGNOF([guint64], typedef unsigned $gint64 guint64;)
AC_CHECK_ALIGNOF([unsigned long])
# Check for libdbus1 - Optional - is only used in the GDBus test cases
#
# 1.2.14 required for dbus_message_set_serial

View File

@ -19,30 +19,268 @@
* Boston, MA 02111-1307, USA.
*/
/*
* This file was originally part of the GNU C Library, and was modified to allow
* user data to be passed in to the sorting function.
*
* Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
* Modified by Maciej Stachowiak (mjs@eazel.com)
*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with GLib
* at ftp://ftp.gtk.org/pub/gtk/.
*/
#include "config.h"
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "galloca.h"
#include "gmem.h"
#include "gqsort.h"
#include "gtestutils.h"
#ifdef HAVE_QSORT_R
/* This file was originally from stdlib/msort.c in gnu libc, just changed
to build inside glib and to not fall back to an unstable quicksort
for large arrays. */
/* An alternative to qsort, with an identical interface.
This file is part of the GNU C Library.
Copyright (C) 1992,95-97,99,2000,01,02,04,07 Free Software Foundation, Inc.
Written by Mike Haertel, September 1988.
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, see
<http://www.gnu.org/licenses/>. */
struct msort_param
{
size_t s;
size_t var;
GCompareDataFunc cmp;
void *arg;
char *t;
};
static void msort_with_tmp (const struct msort_param *p, void *b, size_t n);
static void
msort_with_tmp (const struct msort_param *p, void *b, size_t n)
{
char *b1, *b2;
size_t n1, n2;
if (n <= 1)
return;
n1 = n / 2;
n2 = n - n1;
b1 = b;
b2 = (char *) b + (n1 * p->s);
msort_with_tmp (p, b1, n1);
msort_with_tmp (p, b2, n2);
char *tmp = p->t;
const size_t s = p->s;
GCompareDataFunc cmp = p->cmp;
void *arg = p->arg;
switch (p->var)
{
case 0:
while (n1 > 0 && n2 > 0)
{
if ((*cmp) (b1, b2, arg) <= 0)
{
*(guint32 *) tmp = *(guint32 *) b1;
b1 += sizeof (guint32);
--n1;
}
else
{
*(guint32 *) tmp = *(guint32 *) b2;
b2 += sizeof (guint32);
--n2;
}
tmp += sizeof (guint32);
}
break;
case 1:
while (n1 > 0 && n2 > 0)
{
if ((*cmp) (b1, b2, arg) <= 0)
{
*(guint64 *) tmp = *(guint64 *) b1;
b1 += sizeof (guint64);
--n1;
}
else
{
*(guint64 *) tmp = *(guint64 *) b2;
b2 += sizeof (guint64);
--n2;
}
tmp += sizeof (guint64);
}
break;
case 2:
while (n1 > 0 && n2 > 0)
{
unsigned long *tmpl = (unsigned long *) tmp;
unsigned long *bl;
tmp += s;
if ((*cmp) (b1, b2, arg) <= 0)
{
bl = (unsigned long *) b1;
b1 += s;
--n1;
}
else
{
bl = (unsigned long *) b2;
b2 += s;
--n2;
}
while (tmpl < (unsigned long *) tmp)
*tmpl++ = *bl++;
}
break;
case 3:
while (n1 > 0 && n2 > 0)
{
if ((*cmp) (*(const void **) b1, *(const void **) b2, arg) <= 0)
{
*(void **) tmp = *(void **) b1;
b1 += sizeof (void *);
--n1;
}
else
{
*(void **) tmp = *(void **) b2;
b2 += sizeof (void *);
--n2;
}
tmp += sizeof (void *);
}
break;
default:
while (n1 > 0 && n2 > 0)
{
if ((*cmp) (b1, b2, arg) <= 0)
{
memcpy (tmp, b1, s);
tmp += s;
b1 += s;
--n1;
}
else
{
mempcpy (tmp, b2, s);
tmp += s;
b2 += s;
--n2;
}
}
break;
}
if (n1 > 0)
memcpy (tmp, b1, n1 * s);
memcpy (b, p->t, (n - n2) * s);
}
static void
msort_r (void *b, size_t n, size_t s, GCompareDataFunc cmp, void *arg)
{
size_t size = n * s;
char *tmp = NULL;
struct msort_param p;
/* For large object sizes use indirect sorting. */
if (s > 32)
size = 2 * n * sizeof (void *) + s;
if (size < 1024)
/* The temporary array is small, so put it on the stack. */
p.t = g_alloca (size);
else
{
/* It's large, so malloc it. */
tmp = g_malloc (size);
p.t = tmp;
}
p.s = s;
p.var = 4;
p.cmp = cmp;
p.arg = arg;
if (s > 32)
{
/* Indirect sorting. */
char *ip = (char *) b;
void **tp = (void **) (p.t + n * sizeof (void *));
void **t = tp;
void *tmp_storage = (void *) (tp + n);
while ((void *) t < tmp_storage)
{
*t++ = ip;
ip += s;
}
p.s = sizeof (void *);
p.var = 3;
msort_with_tmp (&p, p.t + n * sizeof (void *), n);
/* tp[0] .. tp[n - 1] is now sorted, copy around entries of
the original array. Knuth vol. 3 (2nd ed.) exercise 5.2-10. */
char *kp;
size_t i;
for (i = 0, ip = (char *) b; i < n; i++, ip += s)
if ((kp = tp[i]) != ip)
{
size_t j = i;
char *jp = ip;
memcpy (tmp_storage, ip, s);
do
{
size_t k = (kp - (char *) b) / s;
tp[j] = jp;
memcpy (jp, kp, s);
j = k;
jp = kp;
kp = tp[k];
}
while (kp != ip);
tp[j] = jp;
memcpy (jp, tmp_storage, s);
}
}
else
{
if ((s & (sizeof (guint32) - 1)) == 0
&& ((char *) b - (char *) 0) % ALIGNOF_GUINT32 == 0)
{
if (s == sizeof (guint32))
p.var = 0;
else if (s == sizeof (guint64)
&& ((char *) b - (char *) 0) % ALIGNOF_GUINT64 == 0)
p.var = 1;
else if ((s & (sizeof (unsigned long) - 1)) == 0
&& ((char *) b - (char *) 0)
% ALIGNOF_UNSIGNED_LONG == 0)
p.var = 2;
}
msort_with_tmp (&p, b, n);
}
g_free (tmp);
}
/**
* g_qsort_with_data:
@ -54,6 +292,8 @@
*
* This is just like the standard C qsort() function, but
* the comparison routine accepts a user data argument.
*
* This is guaranteed to be a stable sort since version 2.32.
*/
void
g_qsort_with_data (gconstpointer pbase,
@ -62,239 +302,5 @@ g_qsort_with_data (gconstpointer pbase,
GCompareDataFunc compare_func,
gpointer user_data)
{
qsort_r ((gpointer)pbase, total_elems, size, compare_func, user_data);
return msort_r (pbase, total_elems, size, compare_func, user_data);
}
#else
/* 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 4 #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 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
g_qsort_with_data (gconstpointer pbase,
gint total_elems,
gsize size,
GCompareDataFunc compare_func,
gpointer user_data)
{
register char *base_ptr = (char *) pbase;
const size_t max_thresh = MAX_THRESH * size;
g_return_if_fail (total_elems >= 0);
g_return_if_fail (pbase != NULL || total_elems == 0);
g_return_if_fail (compare_func != NULL);
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;
PUSH (NULL, NULL);
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 ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
SWAP (mid, lo, size);
if ((*compare_func) ((void *) hi, (void *) mid, user_data) < 0)
SWAP (mid, hi, size);
else
goto jump_over;
if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 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 ((*compare_func) ((void *) left_ptr, (void *) mid, user_data) < 0)
left_ptr += size;
while ((*compare_func) ((void *) mid, (void *) right_ptr, user_data) < 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!). */
#define min(x, y) ((x) < (y) ? (x) : (y))
{
char *const 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 ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 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 ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 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;
}
}
}
}
}
#endif /* HAVE_QSORT_R */

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@ -48,12 +48,51 @@ test_sort_basic (void)
g_free (data);
}
typedef struct {
int val;
int i;
} SortItem;
static int
item_compare_data (gconstpointer p1, gconstpointer p2, gpointer data)
{
const SortItem *i1 = p1;
const SortItem *i2 = p2;
return i1->val - i2->val;
}
static void
test_sort_stable (void)
{
SortItem *data;
gint i;
data = g_malloc (10000 * sizeof (SortItem));
for (i = 0; i < 10000; i++)
{
data[i].val = g_random_int_range (0, 10000);
data[i].i = i;
}
g_qsort_with_data (data, 10000, sizeof (SortItem), item_compare_data, NULL);
for (i = 1; i < 10000; i++)
{
g_assert_cmpint (data[i -1].val, <=, data[i].val);
if (data[i -1].val == data[i].val)
g_assert_cmpint (data[i -1].i, <, data[i].i);
}
g_free (data);
}
int
main (int argc, char *argv[])
{
g_test_init (&argc, &argv, NULL);
g_test_add_func ("/sort/basic", test_sort_basic);
g_test_add_func ("/sort/stable", test_sort_stable);
return g_test_run ();
}