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#include <pthread.h>
#include <stdlib.h>
#include <limits.h>
/************
* kt_for() *
************/
struct kt_for_t;
typedef struct {
struct kt_for_t *t;
long i;
} ktf_worker_t;
typedef struct kt_for_t {
int n_threads;
long n;
ktf_worker_t *w;
void (*func)(void*,long,int);
void *data;
} kt_for_t;
static inline long steal_work(kt_for_t *t)
{
int i, min_i = -1;
long k, min = LONG_MAX;
for (i = 0; i < t->n_threads; ++i)
if (min > t->w[i].i) min = t->w[i].i, min_i = i;
k = __sync_fetch_and_add(&t->w[min_i].i, t->n_threads);
return k >= t->n? -1 : k;
}
static void *ktf_worker(void *data)
{
ktf_worker_t *w = (ktf_worker_t*)data;
long i;
for (;;) {
i = __sync_fetch_and_add(&w->i, w->t->n_threads);
if (i >= w->t->n) break;
w->t->func(w->t->data, i, w - w->t->w);
}
while ((i = steal_work(w->t)) >= 0)
w->t->func(w->t->data, i, w - w->t->w);
pthread_exit(0);
}
void kt_for(int n_threads, void (*func)(void*,long,int), void *data, long n)
{
if (n_threads > 1) {
int i;
kt_for_t t;
pthread_t *tid;
t.func = func, t.data = data, t.n_threads = n_threads, t.n = n;
t.w = (ktf_worker_t*)alloca(n_threads * sizeof(ktf_worker_t));
tid = (pthread_t*)alloca(n_threads * sizeof(pthread_t));
for (i = 0; i < n_threads; ++i)
t.w[i].t = &t, t.w[i].i = i;
for (i = 0; i < n_threads; ++i) pthread_create(&tid[i], 0, ktf_worker, &t.w[i]);
for (i = 0; i < n_threads; ++i) pthread_join(tid[i], 0);
} else {
long j;
for (j = 0; j < n; ++j) func(data, j, 0);
}
}
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