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llama : minimize swaps when reordering logits

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This reduces overhead when running hellaswag
on thousands of sequences with very small 100k params Mamba models.
This commit is contained in:
Francis Couture-Harpin 2024-06-01 15:01:34 -04:00
parent 72eea49224
commit 18d1c14047
1 changed files with 30 additions and 20 deletions
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llama.cpp
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@ -19828,33 +19828,43 @@ void llama_synchronize(struct llama_context * ctx) {
static void llama_reorder_outputs(struct llama_context * ctx) {
std::vector<size_t> & out_ids = ctx->sbatch.out_ids;
if (!out_ids.empty()) {
std::vector<float> logits_tmp;
std::vector<float> embd_tmp;
uint32_t n_vocab = ctx->model.hparams.n_vocab;
uint32_t n_embd = ctx->model.hparams.n_embd;
int32_t n_outputs = ctx->n_outputs;
GGML_ASSERT((size_t) n_outputs == out_ids.size());
// insertion sort (from https://en.wikipedia.org/wiki/Insertion_sort, but using memmove)
for (int32_t i = 1; i < n_outputs; ++i) {
int32_t j = i;
size_t out_id_tmp = out_ids[i];
while (j > 0 && out_ids[j - 1] > out_id_tmp) { j -= 1; }
if (i - j == 0) { continue; }
memmove(out_ids.data() + j + 1, out_ids.data() + j, (i - j)*sizeof(out_ids[0]));
out_ids[j] = out_id_tmp;
{
bool is_already_sorted = true;
for (int32_t i = 0; i < n_outputs - 1; ++i) {
if (out_ids[i] > out_ids[i + 1]) {
is_already_sorted = false;
break;
}
}
if (is_already_sorted) {
out_ids.clear();
return;
}
}
// TODO: is there something more efficient which also minimizes swaps?
// selection sort, to minimize swaps (from https://en.wikipedia.org/wiki/Selection_sort)
for (int32_t i = 0; i < n_outputs - 1; ++i) {
int32_t j_min = i;
for (int32_t j = i + 1; j < n_outputs; ++j) {
if (out_ids[j] < out_ids[j_min]) {
j_min = j;
}
}
if (j_min == i) { continue; }
std::swap(out_ids[i], out_ids[j_min]);
if (ctx->logits_size > 0) {
// only allocate once something needs to be moved
if (logits_tmp.empty()) { logits_tmp.resize(n_vocab); }
memcpy(logits_tmp.data(), ctx->logits + i*n_vocab, n_vocab*sizeof(float));
memmove(ctx->logits + (j + 1)*n_vocab, ctx->logits + j*n_vocab, (i - j)*n_vocab*sizeof(float));
memcpy(ctx->logits + j*n_vocab, logits_tmp.data(), n_vocab*sizeof(float));
for (uint32_t k = 0; k < n_vocab; k++) {
std::swap(ctx->logits[i*n_vocab + k], ctx->logits[j_min*n_vocab + k]);
}
}
if (ctx->embd_size > 0) {
// only allocate once something needs to be moved
if (embd_tmp.empty()) { embd_tmp.resize(n_embd); }
memcpy(embd_tmp.data(), ctx->embd + i*n_embd, n_embd*sizeof(float));
memmove(ctx->embd + (j + 1)*n_embd, ctx->embd + j*n_embd, (i - j)*n_embd*sizeof(float));
memcpy(ctx->embd + j*n_embd, embd_tmp.data(), n_embd*sizeof(float));
for (uint32_t k = 0; k < n_embd; k++) {
std::swap(ctx->embd[i*n_embd + k], ctx->embd[j_min*n_embd + k]);
}
}
}
std::fill(ctx->output_ids.begin(), ctx->output_ids.end(), -1);