void * avx512_fma(void *args_in)
{
/* Thread input */
struct thread_args *args;
const int n_avx512 = VFMAPS_LATENCY;
const __m512 add0 = _mm512_set1_ps((float) 1e-6);
const __m512 mul0 = _mm512_set1_ps((float) (1. + 1e-6));
__m512 r[n_avx512];
// Declare as volatile to prevent removal during optimisation
volatile float result;
long r_max, i;
int j;
double runtime, flops;
Stopwatch *t;
/* Read inputs */
args = (struct thread_args *) args_in;
t = stopwatch_create(args->timer_type);
for (j = 0; j < n_avx512; j++) {
r[j] = _mm512_set1_ps((float) j);
}
/* Add over registers r0-r4, multiply over r5-r9, and rely on pipelining,
* OOO execution, and latency difference (3 vs 5 cycles) for 2x FLOPs
*/
runtime_flag = 0;
r_max = 1;
do {
pthread_barrier_wait(&timer_barrier);
t->start(t);
for (i = 0; i < r_max; i++) {
#pragma unroll(n_avx512)
for (j = 0; j < n_avx512; j++)
r[j] = _mm512_fmadd_ps(r[j], mul0, add0);
}
t->stop(t);
runtime = t->runtime(t);
/* Set runtime flag if any thread exceeds runtime limit */
if (runtime > args->min_runtime) {
pthread_mutex_lock(&runtime_mutex);
runtime_flag = 1;
pthread_mutex_unlock(&runtime_mutex);
}
pthread_barrier_wait(&timer_barrier);
if (!runtime_flag) r_max *= 2;
} while (!runtime_flag);
/* In order to prevent removal of the prior loop by optimisers,
* sum the register values and save the result as volatile. */
for (j = 0; j < n_avx512; j++)
r[0] = _mm512_add_ps(r[0], r[j]);
result = reduce_AVX512(r[0]);
/* (iter) * (16 instr / reg) * (2 flops / instr) * (n_avx512 reg / iter) */
flops = r_max * 16 * 2 * n_avx512 / runtime;
/* Cleanup */
t->destroy(t);
/* Thread output */
args->runtime = runtime;
args->flops = flops;
args->bw_load = 0.;
args->bw_store = 0.;
pthread_exit(NULL);
}
