multithreading ?
/*
* multiple-thread quick-sort.
* Works fine on uniprocessor machines as well.
*/
#include
#include
#include
/* don't create more threads for less than this */
#define SLICE_THRESH 4096
/* how many threads per lwp */
#define THR_PER_LWP 4
/* cast the void to a one byte quanitity and compute the offset */
#define SUB(a, n) ((void *) (((unsigned char *) (a)) + ((n) * width)))
typedef struct {
void *sa_base;
int sa_nel;
size_t sa_width;
int (*sa_compar)(const void *, const void *);
} sort_args_t;
/* for all instances of quicksort */
static int threads_avail;
#define SWAP(a, i, j, width)
{
int n;
unsigned char uc;
unsigned short us;
unsigned long ul;
unsigned long long ull;
if (SUB(a, i) == pivot)
pivot = SUB(a, j);
else if (SUB(a, j) == pivot)
pivot = SUB(a, i);
/* one of the more convoluted swaps I've done */
switch(width) {
case 1:
uc = *((unsigned char *) SUB(a, i));
*((unsigned char *) SUB(a, i)) = *((unsigned char *) SUB(a, j));
*((unsigned char *) SUB(a, j)) = uc;
break;
case 2:
us = *((unsigned short *) SUB(a, i));
*((unsigned short *) SUB(a, i)) = *((unsigned short *) SUB(a, j));
*((unsigned short *) SUB(a, j)) = us;
break;
case 4:
ul = *((unsigned long *) SUB(a, i));
*((unsigned long *) SUB(a, i)) = *((unsigned long *) SUB(a, j));
*((unsigned long *) SUB(a, j)) = ul;
break;
case 8:
ull = *((unsigned long long *) SUB(a, i));
*((unsigned long long *) SUB(a,i)) = *((unsigned long long *) SUB(a,j));
*((unsigned long long *) SUB(a, j)) = ull;
break;
default:
for(n=0; nsa_base;
int n = sargs->sa_nel;
int width = sargs->sa_width;
int (*compar)(const void *, const void *) = sargs->sa_compar;
register int i;
register int j;
int z;
int thread_count = 0;
void *t;
void *b[3];
void *pivot = 0;
sort_args_t sort_args[2];
thread_t tid;
/* find the pivot point */
switch(n) {
case 0:
case 1:
return 0;
case 2:
if ((*compar)(SUB(a, 0), SUB(a, 1)) > 0) {
SWAP(a, 0, 1, width);
}
return 0;
case 3:
/* three sort */
if ((*compar)(SUB(a, 0), SUB(a, 1)) > 0) {
SWAP(a, 0, 1, width);
}
/* the first two are now ordered, now order the second two */
if ((*compar)(SUB(a, 2), SUB(a, 1)) < 0) {
SWAP(a, 2, 1, width);
}
/* should the second be moved to the first? */
if ((*compar)(SUB(a, 1), SUB(a, 0)) < 0) {
SWAP(a, 1, 0, width);
}
return 0;
default:
if (n > 3) {
b[0] = SUB(a, 0);
b[1] = SUB(a, n / 2);
b[2] = SUB(a, n - 1);
/* three sort */
if ((*compar)(b[0], b[1]) > 0) {
t = b[0];
b[0] = b[1];
b[1] = t;
}
/* the first two are now ordered, now order the second two */
if ((*compar)(b[2], b[1]) < 0) {
t = b[1];
b[1] = b[2];
b[2] = t;
}
/* should the second be moved to the first? */
if ((*compar)(b[1], b[0]) < 0) {
t = b[0];
b[0] = b[1];
b[1] = t;
}
if ((*compar)(b[0], b[2]) != 0)
if ((*compar)(b[0], b[1]) < 0)
pivot = b[1];
else
pivot = b[2];
}
break;
}
if (pivot == 0)
for(i=1; i 0) ? SUB(a, 0) : SUB(a, i);
break;
}
}
if (pivot == 0)
return;
/* sort */
i = 0;
j = n - 1;
while(i <= j) {
while((*compar)(SUB(a, i), pivot) < 0)
++i;
while((*compar)(SUB(a, j), pivot) >= 0)
--j;
if (i < j) {
SWAP(a, i, j, width);
++i;
--j;
}
}
/* sort the sides judiciously */
switch(i) {
case 0:
case 1:
break;
case 2:
if ((*compar)(SUB(a, 0), SUB(a, 1)) > 0) {
SWAP(a, 0, 1, width);
}
break;
case 3:
/* three sort */
if ((*compar)(SUB(a, 0), SUB(a, 1)) > 0) {
SWAP(a, 0, 1, width);
}
/* the first two are now ordered, now order the second two */
if ((*compar)(SUB(a, 2), SUB(a, 1)) < 0) {
SWAP(a, 2, 1, width);
}
/* should the second be moved to the first? */
if ((*compar)(SUB(a, 1), SUB(a, 0)) < 0) {
SWAP(a, 1, 0, width);
}
break;
default:
sort_args[0].sa_base = a;
sort_args[0].sa_nel = i;
sort_args[0].sa_width = width;
sort_args[0].sa_compar = compar;
if ((threads_avail > 0) && (i > SLICE_THRESH)) {
threads_avail--;
thr_create(0, 0, _quicksort, &sort_args[0], 0, &tid);
thread_count = 1;
} else
_quicksort(&sort_args[0]);
break;
}
j = n - i;
switch(j) {
case 1:
break;
case 2:
if ((*compar)(SUB(a, i), SUB(a, i + 1)) > 0) {
SWAP(a, i, i + 1, width);
}
break;
case 3:
/* three sort */
if ((*compar)(SUB(a, i), SUB(a, i + 1)) > 0) {
SWAP(a, i, i + 1, width);
}
/* the first two are now ordered, now order the second two */
if ((*compar)(SUB(a, i + 2), SUB(a, i + 1)) < 0) {
SWAP(a, i + 2, i + 1, width);
}
/* should the second be moved to the first? */
if ((*compar)(SUB(a, i + 1), SUB(a, i)) < 0) {
SWAP(a, i + 1, i, width);
}
break;
default:
sort_args[1].sa_base = SUB(a, i);
sort_args[1].sa_nel = j;
sort_args[1].sa_width = width;
sort_args[1].sa_compar = compar;
if ((thread_count == 0) && (threads_avail > 0) && (i > SLICE_THRESH)) {
threads_avail--;
thr_create(0, 0, _quicksort, &sort_args[1], 0, &tid);
thread_count = 1;
} else
_quicksort(&sort_args[1]);
break;
}
if (thread_count) {
thr_join(tid, 0, 0);
threads_avail++;
}
return 0;
}
void
quicksort(void *a, size_t n, size_t width,
int (*compar)(const void *, const void *))
{
static int ncpus = -1;
sort_args_t sort_args;
if (ncpus == -1) {
ncpus = sysconf( _SC_NPROCESSORS_ONLN);
/* lwp for each cpu */
if ((ncpus > 1) && (thr_getconcurrency() < ncpus))
thr_setconcurrency(ncpus);
/* thread count not to exceed THR_PER_LWP per lwp */
threads_avail = (ncpus == 1) ? 0 : (ncpus * THR_PER_LWP);
}
sort_args.sa_base = a;
sort_args.sa_nel = n;
sort_args.sa_width = width;
sort_args.sa_compar = compar;
(void) _quicksort(&sort_args);
}
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