vbatts/llama.cpp
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ggml : improve graph build time via hash table lookup (#2329)

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* improve graph build time

* ggml_tensor : use 1 bit per flag

* use a hash table instead
This commit is contained in:
slaren 2023-07-25 14:32:20 +02:00 • committed by GitHub
parent 82552b7f54
commit da1889834a
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 42 additions and 12 deletions
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43
ggml.c
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@ -15665,6 +15665,34 @@ static void ggml_compute_backward(struct ggml_context * ctx, struct ggml_tensor
}
}
static_assert(GGML_GRAPH_HASHTABLE_SIZE > GGML_MAX_NODES * 2, "GGML_GRAPH_HT_SIZE is too small");
static size_t hash(void * p) {
return (size_t)p % GGML_GRAPH_HASHTABLE_SIZE;
}
static bool hash_insert(void * hash_table[], void * p) {
size_t h = hash(p);
// linear probing
size_t i = h;
while (hash_table[i] != NULL && hash_table[i] != p) {
i = (i + 1) % GGML_GRAPH_HASHTABLE_SIZE;
if (i == h) {
// hash table is full
GGML_ASSERT(false);
}
}
if (hash_table[i] == p) {
return true;
}
// insert
hash_table[i] = p;
return false;
}
static void ggml_visit_parents(struct ggml_cgraph * cgraph, struct ggml_tensor * node) {
if (node->grad == NULL) {
// this usually happens when we generate intermediate nodes from constants in the backward pass
@ -15675,16 +15703,8 @@ static void ggml_visit_parents(struct ggml_cgraph * cgraph, struct ggml_tensor *
}
// check if already visited
for (int i = 0; i < cgraph->n_nodes; i++) {
if (cgraph->nodes[i] == node) {
return;
}
}
for (int i = 0; i < cgraph->n_leafs; i++) {
if (cgraph->leafs[i] == node) {
return;
}
if (hash_insert(cgraph->visited_hash_table, node)) {
return;
}
for (int i = 0; i < GGML_MAX_SRC; ++i) {
@ -15747,6 +15767,7 @@ struct ggml_cgraph ggml_build_forward(struct ggml_tensor * tensor) {
/*.nodes =*/ { NULL },
/*.grads =*/ { NULL },
/*.leafs =*/ { NULL },
/*.hash_table =*/ { NULL },
/*.perf_runs =*/ 0,
/*.perf_cycles =*/ 0,
/*.perf_time_us =*/ 0,
@ -15788,7 +15809,7 @@ struct ggml_cgraph ggml_build_backward(struct ggml_context * ctx, struct ggml_cg
if (node->is_param) {
GGML_PRINT_DEBUG("%s: found root node %p\n", __func__, (void *) node);
ggml_build_forward_impl(&result, node->grad, true);
ggml_build_forward_expand(&result, node->grad);
}
}