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#pragma once
//
// common/ngram-map.h: structures used to manage a map from n-grams to a list of m-grams
//
// These structures are used to do a lookup of n-grams followed by m-grams in token history.
//
// There are two algorithms implemented:
// 1. ngram_simple: lookup of n-grams followed by m-grams in token history.
// 2. ngram_map: lookup of n-grams followed by m-grams in token history using a map.
// The map is a vector of key n-grams, and for each key n-gram there is a list of value m-grams.
//
// ref: https://github.com/ggml-org/llama.cpp/pull/18471
//
#include "llama.h"
#include "common.h"
#include <vector>
// n-gram simple
//
// config of n-gram simple.
struct common_ngram_simple_config {
uint16_t size_ngram; // size of n-grams to lookup in self-mode
uint16_t size_mgram; // size of m-grams to draft in self-mode
uint16_t check_rate; // check for speculative decoding without draft model for each check_rate token
};
// Searches for a n-gram in the history and checks whether a draft sequence should be generated.
llama_tokens common_ngram_simple_draft(
const common_ngram_simple_config & config,
const llama_tokens & tokens, llama_token sampled);
// n-gram map
//
// maximum number of m-gram values stored for each key n-gram.
#define COMMON_NGRAM_MAX_VALUES 4
// number of entries in the (optional, size 0 to disable) map from ngram-hash to ngram-index.
#define COMMON_NGRAM_HASH_MAP_SIZE 262144
// statistics of a m-gram after a known n-gram
struct common_ngram_map_value {
size_t value_idx = 0; // index of value m-gram in token-history (0 if unused)
uint16_t value_num = 0; // number of occurences of this value m-gram after the key n-gram (0 in an unused values-slot)
int16_t n_accepted = -1; // number of accepted tokens at last draft (-1 if unused)
};
// statistics of a n-gram
struct common_ngram_map_key {
size_t key_idx; // index of key n-gram in token-history
size_t stat_idx; // index of last token of stastistics computation (key_num, values)
uint16_t key_num; // number of occurences of this key n-gram in token-history
common_ngram_map_value values[COMMON_NGRAM_MAX_VALUES]; // some known values after the key
};
// map from n-grams to following m-grams in token-history
struct common_ngram_map {
uint16_t size_key; // size of key n-grams
uint16_t size_value; // size of value m-grams
bool key_only; // true if only key n-grams are used, no values.
std::vector<common_ngram_map_key> keys; // key n-grams which occur several times in token-history
uint16_t check_rate; // check for speculative decoding without draft model for each check_rate token
uint16_t min_hits; // minimum number of key hits to consider a draft
bool show_key_map_stats = false; // true, if statitics of the key_map should be printed.
common_ngram_map(uint16_t sz_key, uint16_t sz_value, bool only_keys,
uint16_t check_rate, uint16_t min_hits)
: size_key(sz_key), size_value(sz_value), key_only(only_keys),
check_rate(check_rate), min_hits(min_hits) {
key_map.resize(COMMON_NGRAM_HASH_MAP_SIZE); // 2^18 hash entries, 0 entries if key_map shouldn't be used
}
// In reasoning chats the previous reasoning block will be removed from context history.
// A rebuild of the ngram map is needed after that.
size_t size_last_begin = 0; // number of tokens at previous start of generation
bool last_draft_created = false; // true if a draft was created at last call.
size_t last_draft_key_idx = 0; // index of last key used for draft generation (0 = no draft)
uint16_t last_draft_value_idx = 0; // index of last value used for draft generation.
size_t idx_last_check = 0; // index of last check in context history
// optional map "hash to ngram-index" for faster lookup of n-grams. map is empty if unused.
//
// uint32_t instead of size_t (size of current histories is << UINT32_MAX)
std::vector<uint32_t> key_map; // key_map[hash] = index of ngram in context window
uint32_t key_map_last_idx = 0; // index of the last ngram added to key_map
};
// Initialize the n-gram map with the given token history.
// map: the ngram map to initialize.
// tokens: the token history to base the map on.
void common_ngram_map_begin(
common_ngram_map & map,
const llama_tokens & tokens);
// Searches for the n-gram in the history and checks whether a draft sequence should be generated.
// map: the ngram map to search in.
// inp: the tokens generated so far.
// sampled: the token that was just sampled.
// draft: vector to store the draft tokens, initially empty.
void common_ngram_map_draft(
common_ngram_map & map,
const llama_tokens & inp, llama_token sampled,
llama_tokens & draft);
// Update the statistics of a value after a draft was processed.
void common_ngram_map_accept(common_ngram_map & map, uint16_t n_accepted);
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