speculative : add tree-based sampling example (#3624)

* sampling : one sequence per sampling context

ggml-ci

* speculative : add tree-based sampling support

ggml-ci

* speculative : reuse the n_parallel CLI param

* speculative : refactor sampling

* examples : fix build after sampling refactoring

ggml-ci

* batched : fix n_seq_id

* sampling : fix malloc

ggml-ci

* swift : fix build

ggml-ci

* swift : try to fix build

ggml-ci

* prompts : add assistant.txt

* common : add llama_batch_add() and llama_batch_clear() helpers

* speculative : minor refactor

ggml-ci

* minor : comments + rename

ggml-ci

* speculative : fix off-by-one for n_drafted

* speculative : fix the n_drafted fix + p constants
This commit is contained in:
Georgi Gerganov 2023-10-18 16:21:57 +03:00 committed by GitHub
parent c67fe68e41
commit 0e89203b51
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GPG key ID: 4AEE18F83AFDEB23
21 changed files with 737 additions and 578 deletions

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@ -2,13 +2,25 @@
#include "common.h"
#include "llama.h"
#include "grammar-parser.h"
#include <cmath>
#include <cstdio>
#include <string>
#include <vector>
struct seq_draft {
bool active = false;
bool drafting = false;
bool skip = false;
int i_batch_dft = 0;
std::vector<int> i_batch_tgt;
std::vector<llama_token> tokens;
struct llama_sampling_context * ctx_sampling;
};
int main(int argc, char ** argv) {
gpt_params params;
@ -21,6 +33,13 @@ int main(int argc, char ** argv) {
return 1;
}
// max number of parallel drafting sequences (i.e. tree branches)
const int n_seq_dft = params.n_parallel;
// TODO: make this configurable
const float p_accept = 0.4f;
const float p_split = 0.3f;
#ifndef LOG_DISABLE_LOGS
log_set_target(log_filename_generator("speculative", "log"));
LOG_TEE("Log start\n");
@ -77,8 +96,6 @@ int main(int argc, char ** argv) {
const auto t_enc_end = ggml_time_us();
// the 2 models should have the same vocab
const int n_ctx = llama_n_ctx(ctx_tgt);
const int n_vocab = llama_n_vocab(model_tgt);
//GGML_ASSERT(n_vocab == llama_n_vocab(model_dft));
// how many tokens to draft each time
@ -91,60 +108,58 @@ int main(int argc, char ** argv) {
int n_past_tgt = inp.size();
int n_past_dft = inp.size();
std::vector<llama_token> drafted;
std::vector<llama_token> last_tokens(n_ctx);
std::fill(last_tokens.begin(), last_tokens.end(), 0);
for (auto & id : inp) {
last_tokens.erase(last_tokens.begin());
last_tokens.push_back(id);
}
std::vector<llama_token_data> candidates;
candidates.reserve(n_vocab);
// used to determine end of generation
bool has_eos = false;
// grammar stuff
struct llama_grammar * grammar_dft = NULL;
struct llama_grammar * grammar_tgt = NULL;
// target model sampling context
struct llama_sampling_context * ctx_sampling = llama_sampling_init(params);
grammar_parser::parse_state parsed_grammar;
// draft sequence data
std::vector<seq_draft> drafts(n_seq_dft);
// if requested - load the grammar, error checking is omitted for brevity
if (!params.grammar.empty()) {
parsed_grammar = grammar_parser::parse(params.grammar.c_str());
// will be empty (default) if there are parse errors
if (parsed_grammar.rules.empty()) {
return 1;
}
params.grammar.clear(); // the draft samplers will copy the target sampler's grammar
params.sampling_params.temp = 1.0f; // the draft samplers use default temperature
std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
grammar_tgt = llama_grammar_init(grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
for (int s = 0; s < n_seq_dft; ++s) {
drafts[s].ctx_sampling = llama_sampling_init(params);
}
llama_sampling_context ctx_sampling = llama_sampling_context_init(params, grammar_tgt);
llama_batch batch_dft = llama_batch_init(params.n_ctx, 0, 1);
llama_batch batch_tgt = llama_batch_init(params.n_ctx, 0, n_seq_dft);
const auto t_dec_start = ggml_time_us();
while (true) {
LOG("drafted: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_dft, drafted));
// sample from the last token of the prompt
drafts[0].i_batch_tgt.resize(1);
drafts[0].i_batch_tgt[0] = 0;
int i_dft = 0;
while (true) {
// print current draft sequences
for (int s = 0; s < n_seq_dft; ++s) {
if (!drafts[s].active) {
continue;
}
const auto & tokens = drafts[s].tokens;
LOG("draft %d: %s\n", s, LOG_TOKENS_TOSTR_PRETTY(ctx_dft, tokens).c_str());
}
int i_dft = 0;
int s_keep = 0;
while (true) {
// sample from the target model
llama_token id = llama_sampling_sample(ctx_tgt, NULL, ctx_sampling, last_tokens, candidates, i_dft);
LOG("sampling target: s_keep = %3d, i_dft = %3d, i_batch_tgt = %3d\n", s_keep, i_dft, drafts[s_keep].i_batch_tgt[i_dft]);
// remember which tokens were sampled - used for repetition penalties during sampling
last_tokens.erase(last_tokens.begin());
last_tokens.push_back(id);
// sample from the target model
llama_token id = llama_sampling_sample(ctx_sampling, ctx_tgt, NULL, drafts[s_keep].i_batch_tgt[i_dft]);
llama_sampling_accept(ctx_sampling, ctx_tgt, id);
//LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_tgt, last_tokens));
const std::string token_str = llama_token_to_piece(ctx_tgt, id);
printf("%s", token_str.c_str());
fflush(stdout);
@ -154,53 +169,67 @@ int main(int argc, char ** argv) {
++n_predict;
// check if the draft matches the target
if (i_dft < (int) drafted.size() && id == drafted[i_dft]) {
LOG("the sampled target token matches the %dth drafted token (%d, '%s') - accepted\n", i_dft, id, token_str.c_str());
++n_accept;
++n_past_tgt;
++n_past_dft;
++i_dft;
continue;
}
// the drafted token was rejected or we are out of drafted tokens
if (i_dft < (int) drafted.size()) {
LOG("the %dth drafted token (%d, '%s') does not match the sampled target token (%d, '%s') - rejected\n",
i_dft, drafted[i_dft], llama_token_to_piece(ctx_dft, drafted[i_dft]).c_str(), id, token_str.c_str());
} else {
LOG("out of drafted tokens\n");
}
llama_kv_cache_seq_rm(ctx_dft, 0, n_past_dft, -1);
llama_decode(ctx_dft, llama_batch_get_one(&id, 1, n_past_dft, 0));
++n_past_dft;
// heuristic for n_draft
// check if the target token matches any of the drafts
{
const int n_draft_cur = (int) drafted.size();
const bool all_accepted = i_dft == n_draft_cur;
bool matches = false;
LOG("n_draft = %d\n", n_draft);
LOG("n_draft_cur = %d\n", n_draft_cur);
LOG("i_dft = %d\n", i_dft);
LOG("all_accepted = %d\n", all_accepted);
for (int s = 0; s < n_seq_dft; ++s) {
if (!drafts[s].active) {
continue;
}
if (all_accepted && n_draft == n_draft_cur) {
LOG(" - max drafted tokens accepted - n_draft += 8\n");
n_draft = std::min(30, n_draft + 8);
} else if (all_accepted) {
LOG(" - partially drafted tokens accepted - no change\n");
} else {
LOG(" - drafted token rejected - n_draft -= 1\n");
n_draft = std::max(2, n_draft - 1);
if (i_dft < (int) drafts[s].tokens.size() && id == drafts[s].tokens[i_dft]) {
LOG("the sampled target token matches the %dth drafted token of sequence %d (%d, '%s') - accepted\n", i_dft, s, id, token_str.c_str());
s_keep = s;
matches = true;
} else {
drafts[s].active = false;
}
}
if (matches) {
++n_accept;
++n_past_tgt;
++n_past_dft;
++i_dft;
continue;
}
}
drafted.clear();
drafted.push_back(id);
LOG("the sampled target token (%d, '%s') did not match, or we ran out of drafted tokens\n", id, token_str.c_str());
// TODO: simplify
{
LOG("keeping sequence %d\n", s_keep);
llama_kv_cache_seq_keep(ctx_dft, s_keep);
llama_kv_cache_seq_cp (ctx_dft, s_keep, 0, -1, -1);
llama_kv_cache_seq_keep(ctx_dft, 0);
llama_kv_cache_seq_rm (ctx_tgt, s_keep, n_past_tgt, -1);
llama_kv_cache_seq_keep(ctx_tgt, s_keep);
llama_kv_cache_seq_cp (ctx_tgt, s_keep, 0, -1, -1);
llama_kv_cache_seq_keep(ctx_tgt, 0);
}
for (int s = 0; s < n_seq_dft; ++s) {
drafts[s].active = false;
drafts[s].tokens.clear();
drafts[s].i_batch_tgt.clear();
}
// note: will be erased after the speculation phase
drafts[0].tokens.push_back(id);
drafts[0].i_batch_tgt.push_back(0);
llama_batch_clear(batch_dft);
llama_batch_add (batch_dft, id, n_past_dft, { 0 }, true);
llama_kv_cache_seq_rm(ctx_dft, 0, n_past_dft, -1);
llama_decode (ctx_dft, batch_dft);
++n_past_dft;
break;
}
@ -209,78 +238,158 @@ int main(int argc, char ** argv) {
break;
}
if (grammar_tgt) {
if (grammar_dft) {
llama_grammar_free(grammar_dft);
}
// Note: Hardcoded to sequence id 0, if this ever supports parallel generation
// that will need to change.
auto it = ctx_sampling.sequence_contexts.find(0);
GGML_ASSERT(it != ctx_sampling.sequence_contexts.end());
// This is necessary because each sequence id in sequence_contexts
// uses a copy of the original grammar.
grammar_dft = llama_grammar_copy(it->second.grammar);
llama_sampling_cp(ctx_sampling, drafts[0].ctx_sampling);
LOG("copied target grammar to draft grammar\n");
}
// sample n_draft tokens from the draft model using greedy decoding
int n_seq_cur = 1;
int n_past_cur = n_past_dft;
for (int s = 0; s < n_seq_dft; ++s) {
drafts[s].active = false;
drafts[s].drafting = false;
}
drafts[0].active = true;
drafts[0].drafting = true;
drafts[0].i_batch_dft = 0;
llama_batch_clear(batch_tgt);
llama_batch_add (batch_tgt, drafts[0].tokens[0], n_past_tgt, { 0 }, true);
// sample n_draft tokens from the draft model using tree-based sampling
for (int i = 0; i < n_draft; ++i) {
float * logits = llama_get_logits(ctx_dft);
batch_dft.n_tokens = 0;
candidates.clear();
for (llama_token token_id = 0; token_id < n_vocab; token_id++) {
candidates.emplace_back(llama_token_data{token_id, logits[token_id], 0.0f});
for (int s = 0; s < n_seq_dft; ++s) {
drafts[s].skip = false;
}
llama_token_data_array cur_p = { candidates.data(), candidates.size(), false };
for (int s = 0; s < n_seq_dft; ++s) {
if (!drafts[s].drafting || drafts[s].skip) {
continue;
}
if (grammar_dft != NULL) {
llama_sample_grammar(ctx_dft, &cur_p, grammar_dft);
llama_sampling_sample(drafts[s].ctx_sampling, ctx_dft, NULL, drafts[s].i_batch_dft);
const auto & cur_p = drafts[s].ctx_sampling->cur;
for (int k = 0; k < std::min(n_seq_dft + 3, (int) cur_p.size()); ++k) {
LOG(" - draft candidate %3d for seq %3d, pos %3d: %6d (%8.3f) '%s'\n",
k, s, i, cur_p[k].id, cur_p[k].p, llama_token_to_piece(ctx_dft, cur_p[k].id).c_str());
}
if (cur_p[0].p < p_accept) {
LOG("stopping drafting for seq %3d, probability too low: %.3f < 2*%.3f\n", s, cur_p[0].p, cur_p[1].p);
drafts[s].drafting = false;
continue;
}
std::vector<int> sa(1, s);
// attempt to split the branch if the probability is high enough
for (int f = 1; f < 8; ++f) {
if (n_seq_cur < n_seq_dft && cur_p[f].p > p_split) {
LOG("splitting seq %3d into %3d\n", s, n_seq_cur);
llama_kv_cache_seq_rm(ctx_dft, n_seq_cur, -1, -1);
llama_kv_cache_seq_cp(ctx_dft, s, n_seq_cur, -1, -1);
// all previous tokens from this branch are now also part of the new branch
for (int t = 0; t < batch_tgt.n_tokens; ++t) {
for (int p = 0; p < batch_tgt.n_seq_id[t]; ++p) {
if (batch_tgt.seq_id[t][p] == s) {
batch_tgt.seq_id[t][batch_tgt.n_seq_id[t]] = n_seq_cur;
batch_tgt.n_seq_id[t]++;
break;
}
}
}
// copy the draft state
drafts[n_seq_cur].active = true;
drafts[n_seq_cur].drafting = true;
drafts[n_seq_cur].skip = true;
drafts[n_seq_cur].tokens = drafts[s].tokens;
drafts[n_seq_cur].i_batch_dft = drafts[s].i_batch_dft;
drafts[n_seq_cur].i_batch_tgt = drafts[s].i_batch_tgt;
llama_sampling_cp(drafts[s].ctx_sampling, drafts[n_seq_cur].ctx_sampling);
sa.push_back(n_seq_cur);
n_seq_cur++;
} else {
break;
}
}
// add drafted token for each sequence
for (int is = 0; is < (int) sa.size(); ++is) {
const llama_token id = cur_p[is].id;
const int s = sa[is];
llama_sampling_accept(drafts[s].ctx_sampling, ctx_dft, id);
drafts[s].tokens.push_back(id);
// add unique drafted tokens to the target batch
drafts[s].i_batch_tgt.push_back(batch_tgt.n_tokens);
llama_batch_add(batch_tgt, id, n_past_tgt + i + 1, { s }, true);
// no need to evaluate the last drafted token, since we won't use the result
if (batch_tgt.n_tokens > n_draft) {
drafts[s].drafting = false;
continue;
}
// add the token to the batch for batched decoding with the draft model
drafts[s].i_batch_dft = batch_dft.n_tokens;
llama_batch_add(batch_dft, id, n_past_cur, { s }, true);
}
}
// computes softmax and sorts the candidates
llama_sample_softmax(ctx_dft, &cur_p);
for (int i = 0; i < 3; ++i) {
LOG(" - draft candidate %3d: %6d (%8.3f) '%s'\n", i, cur_p.data[i].id, cur_p.data[i].p, llama_token_to_piece(ctx_dft, cur_p.data[i].id).c_str());
}
// TODO: better logic?
if (cur_p.data[0].p < 2*cur_p.data[1].p) {
LOG("stopping drafting, probability too low: %.3f < 2*%.3f\n", cur_p.data[0].p, cur_p.data[1].p);
// no sequence is drafting anymore
if (batch_dft.n_tokens == 0) {
break;
}
// drafted token
const llama_token id = cur_p.data[0].id;
drafted.push_back(id);
// evaluate the drafted tokens on the draft model
llama_decode(ctx_dft, batch_dft);
++n_past_cur;
++n_drafted;
// no need to evaluate the last drafted token, since we won't use the result
if (i == n_draft - 1) {
if (batch_tgt.n_tokens > n_draft) {
break;
}
}
// evaluate the drafted token on the draft model
llama_kv_cache_seq_rm(ctx_dft, 0, n_past_cur, -1);
llama_decode(ctx_dft, llama_batch_get_one(&drafted.back(), 1, n_past_cur, 0));
++n_past_cur;
if (grammar_dft != NULL) {
llama_grammar_accept_token(ctx_dft, grammar_dft, id);
}
// account for the last drafted token that we didn't evaluate
if (batch_tgt.n_tokens > n_draft) {
++n_drafted;
}
// evaluate the target model on the drafted tokens
llama_kv_cache_seq_rm(ctx_tgt, 0, n_past_tgt, -1);
llama_decode(ctx_tgt, llama_batch_get_one(drafted.data(), drafted.size(), n_past_tgt, 0));
++n_past_tgt;
{
llama_kv_cache_seq_keep(ctx_tgt, 0);
for (int s = 1; s < n_seq_dft; ++s) {
llama_kv_cache_seq_cp(ctx_tgt, 0, s, -1, -1);
}
// the first token is always proposed by the traget model before the speculation loop
drafted.erase(drafted.begin());
//LOG("target batch: %s\n", LOG_BATCH_TOSTR_PRETTY(ctx_tgt, batch_tgt));
llama_decode(ctx_tgt, batch_tgt);
++n_past_tgt;
}
// the first token is always proposed by the traget model before the speculation loop so we erase it here
for (int s = 0; s < n_seq_dft; ++s) {
if (!drafts[s].active) {
continue;
}
drafts[s].tokens.erase(drafts[s].tokens.begin());
}
}
auto t_dec_end = ggml_time_us();
@ -288,9 +397,8 @@ int main(int argc, char ** argv) {
LOG_TEE("\n\n");
LOG_TEE("encoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_input, (t_enc_end - t_enc_start) / 1e6f, inp.size() / ((t_enc_end - t_enc_start) / 1e6f));
LOG_TEE("decoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_predict, (t_dec_end - t_dec_start) / 1e6f, n_predict / ((t_dec_end - t_dec_start) / 1e6f));
LOG_TEE("decoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_predict, (t_dec_end - t_dec_start) / 1e6f, n_predict / ((t_dec_end - t_dec_start) / 1e6f));
// TODO: make sure these numbers are computed correctly
LOG_TEE("\n");
LOG_TEE("n_draft = %d\n", n_draft);
LOG_TEE("n_predict = %d\n", n_predict);
@ -304,16 +412,19 @@ int main(int argc, char ** argv) {
LOG_TEE("\ntarget:\n");
llama_print_timings(ctx_tgt);
llama_sampling_free(ctx_sampling);
for (int s = 0; s < n_seq_dft; ++s) {
llama_sampling_free(drafts[s].ctx_sampling);
}
llama_batch_free(batch_dft);
llama_free(ctx_tgt);
llama_free_model(model_tgt);
llama_free(ctx_dft);
llama_free_model(model_dft);
if (grammar_dft != NULL) {
llama_grammar_free(grammar_dft);
llama_grammar_free(grammar_tgt);
}
llama_backend_free();
fprintf(stderr, "\n\n");