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replace heap sort with smoothsort implementation by Valentin Ochs 

Smoothsort is an adaptive variant of heapsort. This version was
written by Valentin Ochs (apo) specifically for inclusion in musl. I
worked with him to get it working in O(1) memory usage even with giant
array element widths, and to optimize it heavily for size and speed.
It's still roughly 4 times as large as the old heap sort
implementation, but roughly 20 times faster given an almost-sorted
array of 1M elements (20 being the base-2 log of 1M), i.e. it really
does reduce O(n log n) to O(n) in the mostly-sorted case. It's still
somewhat slower than glibc's Introsort for random input, but now
considerably faster than glibc when the input is already sorted, or
mostly sorted.
rs-1.0
Rich Felker 15 years ago
parent
4bb9b4f3b4
commit
22263709ed
2 changed files with 197 additions and 32 deletions
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  1. 4
      COPYRIGHT
  2. 225
      src/stdlib/qsort.c

4
COPYRIGHT
View File

@ -19,6 +19,10 @@ The implementation of DES for crypt (src/misc/crypt.c) is Copyright ©
1994 David Burren. It is licensed under a BSD license compatible with
the GNU LGPL.
The smoothsort implementation (src/stdlib/qsort.c) is Copyright © 2011
Valentin Ochs and is licensed under an MIT-style license compatible
with the GNU LGPL.
The x86_64 port was written by Nicholas J. Kain. See individual files
for their copyright status.

225
src/stdlib/qsort.c
View File

@ -1,50 +1,211 @@
/* Copyright (C) 2011 by Valentin Ochs
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
/* Minor changes by Rich Felker for integration in musl, 2011-04-27. */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
/* A simple heap sort implementation.. only in-place O(nlogn) sort I know. */
#include "atomic.h"
#define ntz(x) a_ctz_l((x))
typedef int (*cmpfun)(const void *, const void *);
#define MIN(a, b) ((a)<(b) ? (a) : (b))
static inline int pntz(size_t p[2]) {
int r = ntz(p[0] - 1);
if(r != 0 || (r = 8*sizeof(size_t) + ntz(p[1])) != 8*sizeof(size_t)) {
return r;
}
return 0;
}
static void swap(char *a, char *b, size_t len)
static void cycle(size_t width, unsigned char* ar[], int n)
{
char tmp[256];
unsigned char tmp[256];
size_t l;
while (len) {
l = MIN(sizeof tmp, len);
memcpy(tmp, a, l);
memcpy(a, b, l);
memcpy(b, tmp, l);
a += l;
b += l;
len -= l;
int i;
if(n < 2) {
return;
}
ar[n] = tmp;
while(width) {
l = sizeof(tmp) < width ? sizeof(tmp) : width;
memcpy(ar[n], ar[0], l);
for(i = 0; i < n; i++) {
memcpy(ar[i], ar[i + 1], l);
ar[i] += l;
}
width -= l;
}
}
/* shl() and shr() need n > 0 */
static inline void shl(size_t p[2], int n)
{
if(n >= 8 * sizeof(size_t)) {
n -= 8 * sizeof(size_t);
p[1] = p[0];
p[0] = 0;
}
p[1] <<= n;
p[1] |= p[0] >> (sizeof(size_t) * 8 - n);
p[0] <<= n;
}
static inline void shr(size_t p[2], int n)
{
if(n >= 8 * sizeof(size_t)) {
n -= 8 * sizeof(size_t);
p[0] = p[1];
p[1] = 0;
}
p[0] >>= n;
p[0] |= p[1] << (sizeof(size_t) * 8 - n);
p[1] >>= n;
}
static void sift(unsigned char *head, size_t width, cmpfun cmp, int pshift, size_t lp[])
{
unsigned char *rt, *lf;
unsigned char *ar[14 * sizeof(size_t) + 1];
int i = 1;
ar[0] = head;
while(pshift > 1) {
rt = head - width;
lf = head - width - lp[pshift - 2];
if((*cmp)(ar[0], lf) >= 0 && (*cmp)(ar[0], rt) >= 0) {
break;
}
if((*cmp)(lf, rt) >= 0) {
ar[i++] = lf;
head = lf;
pshift -= 1;
} else {
ar[i++] = rt;
head = rt;
pshift -= 2;
}
}
cycle(width, ar, i);
}
static void sift(char *base, size_t root, size_t nel, size_t width, int (*cmp)(const void *, const void *))
static void trinkle(unsigned char *head, size_t width, cmpfun cmp, size_t pp[2], int pshift, int trusty, size_t lp[])
{
size_t max;
unsigned char *stepson,
*rt, *lf;
size_t p[2];
unsigned char *ar[14 * sizeof(size_t) + 1];
int i = 1;
int trail;
p[0] = pp[0];
p[1] = pp[1];
while (2*root <= nel) {
max = 2*root;
if (max < nel && cmp(base+max*width, base+(max+1)*width) < 0)
max++;
if (max && cmp(base+root*width, base+max*width) < 0) {
swap(base+root*width, base+max*width, width);
root = max;
} else break;
ar[0] = head;
while(p[0] != 1 || p[1] != 0) {
stepson = head - lp[pshift];
if((*cmp)(stepson, ar[0]) <= 0) {
break;
}
if(!trusty && pshift > 1) {
rt = head - width;
lf = head - width - lp[pshift - 2];
if((*cmp)(rt, stepson) >= 0 || (*cmp)(lf, stepson) >= 0) {
break;
}
}
ar[i++] = stepson;
head = stepson;
trail = pntz(p);
shr(p, trail);
pshift += trail;
trusty = 0;
}
if(!trusty) {
cycle(width, ar, i);
sift(head, width, cmp, pshift, lp);
}
}
void qsort(void *_base, size_t nel, size_t width, int (*cmp)(const void *, const void *))
void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
{
char *base = _base;
size_t i;
if (!nel) return;
for (i=(nel+1)/2; i; i--)
sift(base, i-1, nel-1, width, cmp);
for (i=nel-1; i; i--) {
swap(base, base+i*width, width);
sift(base, 0, i-1, width, cmp);
size_t lp[12*sizeof(size_t)];
size_t i, size = width * nel;
unsigned char *head = base,
*high = head + size - width;
size_t p[2] = {1, 0};
int pshift = 1;
int trail;
/* Precompute Leonardo numbers, scaled by element width */
for(lp[0]=lp[1]=width, i=2; (lp[i]=lp[i-2]+lp[i-1]+width) < size; i++);
while(head < high) {
if((p[0] & 3) == 3) {
sift(head, width, cmp, pshift, lp);
shr(p, 2);
pshift += 2;
} else {
if(lp[pshift - 1] >= high - head) {
trinkle(head, width, cmp, p, pshift, 0, lp);
} else {
sift(head, width, cmp, pshift, lp);
}
if(pshift == 1) {
shl(p, 1);
pshift = 0;
} else {
shl(p, pshift - 1);
pshift = 1;
}
}
p[0] |= 1;
head += width;
}
trinkle(head, width, cmp, p, pshift, 0, lp);
while(pshift != 1 || p[0] != 1 || p[1] != 0) {
if(pshift <= 1) {
trail = pntz(p);
shr(p, trail);
pshift += trail;
} else {
shl(p, 2);
pshift -= 2;
p[0] ^= 7;
shr(p, 1);
trinkle(head - lp[pshift] - width, width, cmp, p, pshift + 1, 1, lp);
shl(p, 1);
p[0] |= 1;
trinkle(head - width, width, cmp, p, pshift, 1, lp);
}
head -= width;
}
}

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