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llama.cpp
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llama.cpp/common/ngram-map.cpp

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#include "common.h"
#include "log.h"
#include "ngram-map.h"
#include <cinttypes>
#include <cstdint>
#include <cstdio>
#include <sstream>
// prime number used for LCG hash function (32 bit), it is near (sqrt(5) - 1)/2 * 2^32.
#define LCG_FACTOR 2654435761UL
// Compute the LCG hash of a n-gram of size len at offset start.
static uint32_t common_ngram_map_hash(const llama_tokens & tokens, size_t start, size_t len) {
uint32_t hash = 0;
for (size_t i = 0; i < len; ++i) {
hash = hash * LCG_FACTOR + tokens[start + i];
}
return hash;
}
// Print the values of a sublist of `llama_tokens & inp` to a string in the form [v0, v1, v2, ...].
static std::string common_tokens_to_str(const llama_tokens & inp, size_t start, size_t length) {
std::ostringstream oss;
oss << '[';
for (size_t i = 0; i < length; ++i) {
if (i > 0) {
oss << ", ";
}
oss << inp[start + i];
}
oss << ']';
return oss.str();
}
// n-gram simple
//
/**
* Perform speculative generation using the model's own token history.
* Searches for a matching pattern in the token history and returns draft tokens.
*
* @param state Current state of this implementation
* @param tokens Token history to search in
* @param sampled Last sampled token
* @return Vector of draft tokens, empty if no matching pattern is found
*/
llama_tokens common_ngram_simple_draft(
common_ngram_simple_state & state,
const llama_tokens & tokens, llama_token sampled) {
// Simple implementation of self-speculative decoding without a draft model.
//
const size_t cur_len = tokens.size();
// Only check every check_rate tokens to save compute
// i.e., perform check if (cur_len - idx_last_check) >= check_rate
if (state.idx_last_check + state.config.check_rate > cur_len) {
llama_tokens draft_tokens;
return draft_tokens;
}
size_t n_draft_min = state.config.size_ngram; // size of n-gram to lookup in token history
size_t n_draft_max = state.config.size_mgram; // the m-gram following the found n-gram is used for draft
// vector for tokens we want to verify.
// return empty vector if there is no match.
llama_tokens draft_tokens;
// We need at least n_draft_min + n_draft_max + 1 tokens.
if (cur_len <= static_cast<size_t>(n_draft_min + n_draft_max + 1)) {
return draft_tokens;
}
// pattern search
llama_tokens pattern;
pattern.reserve(n_draft_min);
for (size_t j = cur_len - n_draft_min + 1; j < cur_len; ++j) {
pattern.push_back(tokens[j]);
}
pattern.push_back(sampled); // add the last token to the pattern
// We do a search in the token history.
state.idx_last_check = cur_len;
size_t match_pos = 0; // we ignore position 0, position 0 == no match
// search backwards, but skip the current match (we are currently there)
for (size_t j = cur_len - n_draft_min - 1; j > 0; --j) {
bool match = true;
for (size_t k = 0; k < pattern.size(); ++k) {
if (tokens[j + k] != pattern[k]) {
match = false;
break;
}
}
if (match) {
match_pos = j;
break;
}
}
if (match_pos == 0) {
return draft_tokens;
}
const size_t copy_max = std::min(
n_draft_max,
cur_len - (match_pos + n_draft_min)
);
if (copy_max < n_draft_min) {
return draft_tokens;
}
LOG_DBG("%s: #tokens = %zu: found matching pattern at pos %zu, length %zu, draft length %zu\n",
__func__, cur_len,
match_pos, pattern.size(), copy_max);
draft_tokens.reserve(copy_max);
for (size_t j = 0; j < copy_max; ++j) {
draft_tokens.push_back(tokens[match_pos + n_draft_min + j]);
}
return draft_tokens;
}
// n-gram map
//
// maximum number of counted values of a ngram map value.
#define COMMON_NGRAM_MAX_VALUE_COUNT 16380
void common_ngram_map_begin(
common_ngram_map & map, const llama_tokens & tokens) {
size_t size_begin = tokens.size();
LOG_DBG("%s: begin, idx_last_draft=%zu, new begin=%zu, #keys=%zu\n", __func__,
map.idx_last_check, size_begin, map.keys.size());
size_t count_map_entries_upd = 0;
if (!map.key_map.empty() && size_begin < map.idx_last_check) {
if (map.show_key_map_stats) {
// Print statistics of hash map map_key.
size_t count_nonzero = 0;
uint32_t min_idx = UINT32_MAX;
uint32_t max_idx = 0;
for (size_t i = 0; i < map.key_map.size(); ++i) {
uint32_t key_idx = map.key_map[i];
if (key_idx != 0) {
++count_nonzero;
if (key_idx < min_idx) min_idx = key_idx;
if (key_idx > max_idx) max_idx = key_idx;
}
}
if (count_nonzero == 0) {
min_idx = 0;
}
LOG_INF("%s: key_map stats: entries=%zu, min_idx=%u, max_idx=%u, key_map_last_idx=%u\n",
__func__, count_nonzero, min_idx, max_idx, map.key_map_last_idx);
}
// Update the map from hash to key index (clear outdated entries).
for (size_t i = 0; i < map.key_map.size(); ++i) {
uint32_t key_idx = map.key_map[i];
if (key_idx >= map.size_last_begin) {
map.key_map[i] = 0;
count_map_entries_upd++;
}
}
map.key_map_last_idx = (map.size_last_begin > 0) ? map.size_last_begin - 1 : 0;
}
if (size_begin < map.idx_last_check && !map.keys.empty()) {
// The next token generation will start at index size_begin.
// The tokens between map.size_last_begin and size_begin are no longer valid.
//
// Refresh map: Remove all entries with index >= map.size_last_begin.
size_t count_keys = map.keys.size();
size_t count_keys_del = 0;
size_t count_values_del = 0;
for (int32_t i = map.keys.size() - 1; i >= 0; --i) {
common_ngram_map_key & key = map.keys[i];
if (key.key_idx >= map.size_last_begin) {
// Delete the key.
LOG_DBG("%s: delete key %d at index %zu (>= size_last_begin=%zu)\n", __func__, i, key.key_idx, map.size_last_begin);
map.keys.erase(map.keys.begin() + i);
count_keys_del++;
continue;
}
if (map.key_only) {
continue;
}
// Check the indices of the values.
for (int16_t j = COMMON_NGRAM_MAX_VALUES - 1; j >= 0; --j) {
common_ngram_map_value & value = key.values[j];
if (value.value_idx >= map.size_last_begin) {
// Delete the value.
count_values_del++;
// Move all values after this value to the left.
for (uint16_t k = j; k < COMMON_NGRAM_MAX_VALUES - 1; ++k) {
key.values[k] = key.values[k + 1];
}
// Clear the last value.
key.values[COMMON_NGRAM_MAX_VALUES - 1].value_idx = 0;
key.values[COMMON_NGRAM_MAX_VALUES - 1].value_num = 0;
}
}
if (key.values[0].value_idx == 0) {
// No values left, delete the key.
LOG_DBG("%s: delete key %d at index %zu (no values left)\n", __func__, i, key.key_idx);
map.keys.erase(map.keys.begin() + i);
count_keys_del++;
}
}
LOG_INF("%s: refresh map: idx_last_draft=%zu, new begin=%zu, #keys_checked=%zu, #keys_del=%zu, #values_del=%zu, #hashes_upd=%zu\n", __func__,
map.idx_last_check, size_begin,
count_keys, count_keys_del, count_values_del, count_map_entries_upd);
}
map.idx_last_check = (map.size_last_begin > 0) ? map.size_last_begin - 1 : 0;
map.size_last_begin = size_begin;
}
void common_ngram_map_draft(common_ngram_map & map,
const llama_tokens & inp, llama_token sampled,
llama_tokens & draft) {
// reset last key and value.
map.last_draft_created = false;
map.last_draft_key_idx = 0;
map.last_draft_value_idx = 0;
const size_t cur_len = inp.size();
const uint16_t n = map.size_key;
const uint16_t m = map.size_value;
if (cur_len < static_cast<size_t>(2 * n + m)) {
return;
}
if (cur_len >= static_cast<size_t>(UINT32_MAX)) {
// key_map uses uint32_t instead of size_t.
GGML_ABORT("%s: cur_len exceeds UINT32_MAX: %zu", __func__, cur_len);
}
// Only check every check_rate tokens to save compute
// i.e., perform check if (cur_len - idx_last_check) >= check_rate
if (map.idx_last_check + map.check_rate > cur_len) {
return;
}
map.idx_last_check = cur_len;
// search pattern, the key n-gram
std::vector<llama_token> key_tokens;
key_tokens.reserve(n);
for (size_t j = cur_len - n + 1; j < cur_len; ++j) {
key_tokens.push_back(inp[j]);
}
key_tokens.push_back(sampled);
// search for the key in the map
size_t match_pos = 0;
if (map.size_last_begin > cur_len) {
GGML_ABORT("%s: map.size_last_begin > cur_len: %zu > %zu", __func__, map.size_last_begin, cur_len);
}
if (!map.key_map.empty()) {
// Search for the key in the map key_map from hash of ngrams to index of ngram.
uint32_t idx_hash = (common_ngram_map_hash(key_tokens, 0, n) % map.key_map.size());
uint32_t idx_key = map.key_map[idx_hash];
if (idx_key != 0 && idx_key < cur_len - n - m - 1) {
// Check if the key matches the key at idx_key (because of possible collisions).
bool match = true;
for (size_t k = 0; k < n; ++k) {
if (inp[idx_key + k] != key_tokens[k]) {
match = false;
break;
}
}
LOG_DBG("%s: key hash %x -> idx_key %d: match %d\n", __func__, idx_hash, idx_key, match ? 1 : 0);
if (match) {
match_pos = idx_key;
}
}
}
if (match_pos == 0 && map.size_last_begin > (size_t) (n + m + 1)) {
// Search for the key in [1, map.size_last_begin - n - m -1], descending.
for (size_t j = map.size_last_begin - n - m - 1; j > map.key_map_last_idx; --j) {
// Check if the key matches the key.
bool match = true;
for (size_t k = 0; k < n; ++k) {
if (inp[j + k] != key_tokens[k]) {
match = false;
break;
}
}
if (match) {
match_pos = j;
break;
}
}
}
if (match_pos == 0) {
// In case of a reasoning chat, the part after size_last_begin may be deleted/reordered later.
//
// Search in [size_last_begin, cur_len - n - m - 1], descending.
for (size_t j = cur_len - n - m - 1; j > map.size_last_begin && j > map.key_map_last_idx; --j) {
bool match = true;
for (size_t k = 0; k < n; ++k) {
if (inp[j + k] != key_tokens[k]) {
match = false;
break;
}
}
if (match) {
match_pos = j;
break;
}
}
}
if (match_pos > 0) {
LOG_DBG("%s: cur_len = %zu, n = %d, m = %d, sz_tkns = %zu, sampled = %d, match_pos = %zu\n", __func__,
cur_len, n, m, key_tokens.size(), sampled, match_pos);
}
if (!map.key_map.empty()) {
// Add hashes of new ngrams in key_map.
//
// Use the same order as above.
if (map.size_last_begin > (size_t) (n + m + 1)) {
for (size_t j = map.size_last_begin - n - m - 1; j > map.key_map_last_idx; --j) {
// compute hash and store index of ngram at idx j in the map.
uint32_t idx_hash = (common_ngram_map_hash(inp, j, n) % map.key_map.size());
if (map.key_map[idx_hash] == 0) {
map.key_map[idx_hash] = j; // collisions may occur
}
}
}
for (size_t j = cur_len - n - m - 1; j > map.size_last_begin && j > map.key_map_last_idx; --j) {
// compute hash and store index of ngram at idx j in the map.
uint32_t idx_hash = (common_ngram_map_hash(inp, j, n) % map.key_map.size());
if (map.key_map[idx_hash] == 0) {
map.key_map[idx_hash] = j;
}
}
map.key_map_last_idx = std::max(static_cast<uint32_t>(cur_len - n - m - 1), map.key_map_last_idx);
}
if (match_pos == 0) {
return;
}
// We have a match, now we look for the statistics of the key.
size_t key_offset = map.keys.size(); // offset in the map
// We iterate through the std::vector<common_ngram_map_key> map->keys.
for (size_t i = 0; i < map.keys.size(); ++i) {
bool match = true;
for (size_t j = 0; j < n; ++j) {
if (inp[map.keys[i].key_idx + j] != key_tokens[j]) {
match = false;
break;
}
}
if (match) {
key_offset = i;
break;
}
}
if (key_offset == map.keys.size()) {
// We create a new key-entry, it will get offset key_offset.
common_ngram_map_key new_key;
new_key.key_idx = match_pos;
new_key.stat_idx = 0;
new_key.key_num = 0;
for (int i = 0; i < COMMON_NGRAM_MAX_VALUES; ++i) {
new_key.values[i].value_num = 0;
new_key.values[i].n_accepted = m;
}
map.keys.push_back(new_key);
}
// our key n-gram:
common_ngram_map_key & curr_key = map.keys[key_offset];
// update number of key hits
curr_key.key_num = (uint16_t) std::min((int) map.keys[key_offset].key_num + 1,
(int) COMMON_NGRAM_MAX_VALUE_COUNT);
if (map.key_only) {
// simple mode:
// Fill in the draft with the m tokens following the key.
// We work with value values[0] only.
int n_draft_tokens = std::min((int) m, (int) curr_key.values[0].n_accepted);
for (int i = 0; i < n_draft_tokens; ++i) {
draft.push_back(inp[match_pos + n + i]);
}
LOG_DBG("%s: key_idx = %zu, key_offset = %zu, key_num = %d, draft.size = %zu\n", __func__,
curr_key.key_idx, key_offset, curr_key.key_num, draft.size());
map.last_draft_created = false;
map.last_draft_key_idx = key_offset;
map.last_draft_value_idx = 0; // value 0 is used for simple mode
return;
}
if (curr_key.key_num < map.min_hits) {
// not enough hits to consider this a good draft
LOG_DBG("%s: key_offset = %zu, key_num = %d, min_hits = %d, no draft\n", __func__,
key_offset, curr_key.key_num, map.min_hits);
return;
}
// complex mode: examine the different m-grams after this key n-gram.
//
// determine all (max COMMON_NGRAM_MAX_VALUES) m-grams after the key n-gram.
for (size_t i = curr_key.stat_idx; i <= match_pos; ++i) {
// begins the key n-gram at index i?
bool match_key = true;
for (size_t k = 0; k < n; ++k) {
if (inp[i + k] != key_tokens[k]) {
match_key = false;
break;
}
}
if (!match_key) {
continue;
}
// Do we haven a existing value m-gram or a new one after the key at index i?
size_t idx_begin_value_key = i + n;
int idx_value = -1;
for (int v = 0; v < COMMON_NGRAM_MAX_VALUES; ++v) {
size_t idx_begin_value_v = curr_key.values[v].value_idx;
if (idx_begin_value_v == 0) {
// We found an empty value slot => we found a new value m-gram after the key n-gram.
curr_key.values[v].value_idx = idx_begin_value_key;
curr_key.values[v].value_num = 0;
curr_key.values[v].n_accepted = m;
idx_value = v;
break;
}
bool match = true;
for (size_t j = 0; j < m; ++j) {
if (inp[idx_begin_value_key + j] != inp[idx_begin_value_v + j]) {
match = false;
break;
}
}
if (match) {
// We found an existing value m-gram after the key n-gram.
idx_value = v;
break;
}
}
if (idx_value >= 0) {
// We found a value m-gram of the key n-gram.
curr_key.values[idx_value].value_num = (uint16_t) std::min((int) curr_key.values[idx_value].value_num + 1,
(int) COMMON_NGRAM_MAX_VALUE_COUNT);
}
}
// the statistics are updated up to match_pos.
curr_key.stat_idx = match_pos;
// Do we have a value we could use for the draft?
uint16_t max_occur = 0;
int slot_max = 0;
for (int v = 0; v < COMMON_NGRAM_MAX_VALUES; ++v) {
uint16_t curr_occur = curr_key.values[v].value_num;
if (curr_occur > max_occur) {
max_occur = curr_occur;
slot_max = v;
}
}
// What is sum of the other occurences?
uint32_t sum_occur = 0;
for (int v = 0; v < COMMON_NGRAM_MAX_VALUES; ++v) {
if (v == slot_max) {
continue;
}
uint16_t curr_occur = curr_key.values[v].value_num;
sum_occur += curr_occur;
}
LOG_INF("%s: key_offset = %zu, max_occur = %d, sum_occur = %d, slot_max = %d [%zu/%d, %zu/%d, %zu/%d, %zu/%d]\n", __func__,
key_offset,
max_occur, sum_occur, slot_max,
curr_key.values[0].value_idx, curr_key.values[0].value_num,
curr_key.values[1].value_idx, curr_key.values[1].value_num,
curr_key.values[2].value_idx, curr_key.values[2].value_num,
curr_key.values[3].value_idx, curr_key.values[3].value_num
);
// Print the tokens of the four values (if idx != 0), use LOG_INF
for (int v = 0; v < COMMON_NGRAM_MAX_VALUES; ++v) {
if (curr_key.values[v].value_idx != 0) {
LOG_INF("%s: value[%d] = %s\n", __func__, v, common_tokens_to_str(inp, curr_key.values[v].value_idx, m).c_str());
}
}
if (sum_occur > 0 && max_occur < 2 * sum_occur) {
// The most frequent value is not much more frequent than the other values.
// We do not use the draft.
return;
}
// We use the most frequent value values[slot_max] for the draft.
// Fill in the draft with the m tokens following the key.
int n_draft_tokens = std::min((int) m, (int) curr_key.values[slot_max].n_accepted);
for (int i = 0; i < n_draft_tokens; ++i) {
draft.push_back(inp[match_pos + n + i]);
}
LOG_INF("%s: key_offset = %zu, slot_max = %d, key_num = %d, draft.size = %zu\n", __func__,
key_offset, slot_max,
curr_key.key_num, draft.size());
map.last_draft_created = true;
map.last_draft_key_idx = key_offset;
map.last_draft_value_idx = slot_max; // value used for draft generation.
}
void common_ngram_map_accept(common_ngram_map & map, uint16_t n_accepted) {
if (!map.last_draft_created) {
return;
}
// find the key and its chosen value.
const size_t key_idx = map.last_draft_key_idx;
const size_t val_idx = map.last_draft_value_idx;
// find key corresponding to key_idx.
common_ngram_map_key & curr_key = map.keys[key_idx];
// find value corresponding to val_idx.
struct common_ngram_map_value & curr_value = curr_key.values[val_idx]; // value used for draft generation.
// update the value statistics
LOG_INF("common_ngram_map_send_accepted: n_accepted = %d, prev value_num = %d\n",
n_accepted, curr_value.n_accepted);
curr_value.n_accepted = n_accepted;
}
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