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Usage of Open MP Barrier for thread sync to avoid atomic operations #8002

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Usage of Open MP Barrier for thread sync to avoid atomic operations #8002

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37 changes: 34 additions & 3 deletions ggml.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19033,8 +19033,11 @@ static thread_ret_t ggml_graph_compute_thread(void * data) {
state->ec = GGML_STATUS_ABORTED;
return 0;
}

#ifdef GGML_USE_OPENMP
if (state->ith == 0) {
#else
if (atomic_fetch_sub(&state->shared->n_active, 1) == 1) {
#endif
// all other threads are finished and spinning
// do finalize and init here so we don't have synchronize again
struct ggml_compute_params params = {
Expand Down Expand Up @@ -19094,13 +19097,23 @@ static thread_ret_t ggml_graph_compute_thread(void * data) {
}

task_phase = GGML_TASK_TYPE_INIT;
#ifdef GGML_USE_OPENMP
state->shared->n_active = n_threads;
state->shared->node_n = node_n;
state->shared->node_task = task_phase;
}
#pragma omp barrier
node_n = state->shared->node_n;
task_phase = state->shared->node_task;
#else
atomic_store(&state->shared->n_active, n_threads);
atomic_store(&state->shared->node_n, node_n);
atomic_store(&state->shared->node_task, task_phase);
} else {
ggml_graph_compute_thread_sync_node(&node_n, state, false);
ggml_graph_compute_thread_sync_task(&task_phase, state, false);
}
#endif

// check if we should stop
if (node_n >= cgraph->n_nodes) break;
Expand All @@ -19122,7 +19135,15 @@ static thread_ret_t ggml_graph_compute_thread(void * data) {
ggml_compute_forward(&params, node, state);
}
}

#ifdef GGML_USE_OPENMP
if (state->ith == 0) {
task_phase = GGML_TASK_TYPE_COMPUTE;
state->shared->n_active = n_threads;
state->shared->node_task = task_phase;
}
#pragma omp barrier
task_phase = state->shared->node_task;
#else
if (atomic_fetch_sub(&state->shared->n_active, 1) == 1) {
task_phase = GGML_TASK_TYPE_COMPUTE;
atomic_store(&state->shared->n_active, n_threads);
Expand All @@ -19137,12 +19158,21 @@ static thread_ret_t ggml_graph_compute_thread(void * data) {
const bool do_yield = node_n < 0 || cgraph->nodes[node_n]->op == GGML_OP_MUL_MAT;
ggml_graph_compute_thread_sync_task(&task_phase, state, do_yield);
}
#endif

if (state->ith < n_tasks) {
params.type = GGML_TASK_TYPE_COMPUTE;
ggml_compute_forward(&params, node, state);
}

#ifdef GGML_USE_OPENMP
if (state->ith == 0) {
task_phase = GGML_TASK_TYPE_FINALIZE;
state->shared->n_active = n_threads;
state->shared->node_task = task_phase;
}
#pragma omp barrier
task_phase = state->shared->node_task;
#else
if (atomic_fetch_sub(&state->shared->n_active, 1) == 1) {
task_phase = GGML_TASK_TYPE_FINALIZE;
atomic_store(&state->shared->n_active, n_threads);
Expand All @@ -19151,6 +19181,7 @@ static thread_ret_t ggml_graph_compute_thread(void * data) {
else {
ggml_graph_compute_thread_sync_task(&task_phase, state, false);
}
#endif
}

return 0;
Expand Down