cosmopolitan/libc/alg/qsort.c

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi
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.
*/
#include "libc/alg/alg.h"
#include "libc/assert.h"
#include "libc/nexgen32e/bsf.h"
#include "libc/str/str.h"
asm(".ident\t\"\\n\\n\
Smoothsort (MIT License)\\n\
Copyright 2011 Valentin Ochs\\n\
Discovered by Edsger Dijkstra\"");
asm(".include \"libc/disclaimer.inc\"");
typedef int (*cmpfun)(const void *, const void *, void *);
forceinline unsigned bsfz0(unsigned x) {
if (x) {
return bsf(x);
} else {
return 0;
}
}
forceinline unsigned pntz(unsigned p[2]) {
unsigned r;
assert(p[0] != 0);
r = bsfz0(p[0] - 1);
if (r != 0 ||
(r = 8 * sizeof(unsigned) + bsfz0(p[1])) != 8 * sizeof(unsigned)) {
return r;
}
return 0;
}
static void cycle(size_t width, unsigned char *ar[], size_t n) {
unsigned i, l;
unsigned char tmp[256];
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;
}
}
forceinline void shl(unsigned p[2], size_t n) {
assert(n > 0);
if (n >= CHAR_BIT * sizeof(unsigned)) {
n -= CHAR_BIT * sizeof(unsigned);
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p[1] = p[0];
p[0] = 0;
}
p[1] <<= n;
p[1] |= p[0] >> (sizeof(unsigned) * CHAR_BIT - n);
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p[0] <<= n;
}
forceinline void shr(unsigned p[2], size_t n) {
assert(n > 0);
if (n >= CHAR_BIT * sizeof(unsigned)) {
n -= CHAR_BIT * sizeof(unsigned);
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p[0] = p[1];
p[1] = 0;
}
p[0] >>= n;
p[0] |= p[1] << (sizeof(unsigned) * CHAR_BIT - n);
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p[1] >>= n;
}
static void sift(unsigned char *head, cmpfun cmp, void *arg, int pshift,
unsigned char *ar[hasatleast 14 * sizeof(unsigned) + 1],
unsigned lp[hasatleast 12 * sizeof(unsigned)], size_t width) {
unsigned i;
unsigned char *rt, *lf;
i = 1;
ar[0] = head;
while (pshift > 1) {
rt = head - width;
lf = head - width - lp[pshift - 2];
if ((*cmp)(ar[0], lf, arg) >= 0 && (*cmp)(ar[0], rt, arg) >= 0) {
break;
}
if ((*cmp)(lf, rt, arg) >= 0) {
ar[i++] = lf;
head = lf;
pshift -= 1;
} else {
ar[i++] = rt;
head = rt;
pshift -= 2;
}
}
cycle(width, ar, i);
}
static void trinkle(unsigned char *head, cmpfun cmp, void *arg, unsigned pp[2],
unsigned char *ar[hasatleast 14 * sizeof(unsigned) + 1],
unsigned lp[hasatleast 12 * sizeof(unsigned)], size_t width,
int pshift, int trusty) {
unsigned p[2];
unsigned i, trail;
unsigned char *stepson, *rt, *lf;
i = 1;
p[0] = pp[0];
p[1] = pp[1];
ar[0] = head;
while (p[0] != 1 || p[1] != 0) {
stepson = head - lp[pshift];
if ((*cmp)(stepson, ar[0], arg) <= 0) {
break;
}
if (!trusty && pshift > 1) {
rt = head - width;
lf = head - width - lp[pshift - 2];
if ((*cmp)(rt, stepson, arg) >= 0 || (*cmp)(lf, stepson, arg) >= 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, cmp, arg, pshift, ar, lp, width);
}
}
/**
* Smoothsort is an adaptive linearithmic sorting algorithm that's
* nearly linear on mostly-sorted data, and consumes constant memory.
*/
static noinline void smoothsort(
void *base, size_t count, size_t width, cmpfun cmp, void *arg,
unsigned lp[hasatleast 12 * sizeof(unsigned)],
unsigned char *ar[hasatleast 14 * sizeof(unsigned) + 1]) {
unsigned i, size = width * count;
unsigned char *head, *high;
unsigned p[2] = {1, 0};
unsigned pshift = 1;
unsigned trail;
if (!size) return;
head = (unsigned char *)base;
high = head + size - width;
/* 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, cmp, arg, pshift, ar, lp, width);
shr(p, 2);
pshift += 2;
} else {
if (lp[pshift - 1] >= high - head) {
trinkle(head, cmp, arg, p, ar, lp, width, pshift, 0);
} else {
sift(head, cmp, arg, pshift, ar, lp, width);
}
if (pshift == 1) {
shl(p, 1);
pshift = 0;
} else {
shl(p, pshift - 1);
pshift = 1;
}
}
p[0] |= 1;
head += width;
}
trinkle(head, cmp, arg, p, ar, lp, width, pshift, 0);
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, cmp, arg, p, ar, lp, width, pshift + 1,
1);
shl(p, 1);
p[0] |= 1;
trinkle(head - width, cmp, arg, p, ar, lp, width, pshift, 1);
}
head -= width;
}
}
/**
* Sorts array.
*
* @param base points to an array to sort in-place
* @param count is the item count
* @param width is the size of each item
* @param cmp is a callback returning <0, 0, or >0
* @param arg will optionally be passed as the third argument to cmp
*/
void qsort_r(void *base, size_t count, size_t width, cmpfun cmp, void *arg) {
unsigned lp[12 * sizeof(unsigned)];
unsigned char *ar[14 * sizeof(unsigned) + 1];
smoothsort(base, count, width, (cmpfun)cmp, arg, lp, ar);
}
/**
* Sorts array.
* @see qsort_r() for further details
*/
void qsort(void *base, size_t count, size_t width,
int cmp(const void *, const void *)) {
qsort_r(base, count, width, (cmpfun)cmp, NULL);
}