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Diffstat (limited to 'src/llama-grammar.cpp')
| -rw-r--r-- | src/llama-grammar.cpp | 539 |
1 files changed, 539 insertions, 0 deletions
diff --git a/src/llama-grammar.cpp b/src/llama-grammar.cpp new file mode 100644 index 00000000..bd9322e2 --- /dev/null +++ b/src/llama-grammar.cpp @@ -0,0 +1,539 @@ +#include "llama-grammar.h" + +#include "llama-vocab.h" +#include "llama-sampling.h" + +#include <algorithm> + +// Decodes a UTF-8 string which may end in an incomplete sequence. Adds a terminating 0 for use as +// pointer. If an invalid sequence is encountered, returns `llama_partial_utf8.n_remain == -1`. +std::pair<std::vector<uint32_t>, llama_partial_utf8> decode_utf8( + const std::string & src, + llama_partial_utf8 partial_start) { + static const int lookup[] = { 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 2, 2, 3, 4 }; + const char * pos = src.c_str(); + std::vector<uint32_t> code_points; + + // common english strings have the same number of codepoints and bytes. `+ 1` for the terminating 0. + code_points.reserve(src.size() + 1); + uint32_t value = partial_start.value; + int n_remain = partial_start.n_remain; + + // continue previous decode, if applicable + while (*pos != 0 && n_remain > 0) { + uint8_t next_byte = static_cast<uint8_t>(*pos); + if ((next_byte >> 6) != 2) { + // invalid sequence, abort + code_points.push_back(0); + return std::make_pair(std::move(code_points), llama_partial_utf8{ 0, -1 }); + } + value = (value << 6) + (next_byte & 0x3F); + ++pos; + --n_remain; + } + + if (partial_start.n_remain > 0 && n_remain == 0) { + code_points.push_back(value); + } + + // decode any subsequent utf-8 sequences, which may end in an incomplete one + while (*pos != 0) { + uint8_t first_byte = static_cast<uint8_t>(*pos); + uint8_t highbits = first_byte >> 4; + n_remain = lookup[highbits] - 1; + + if (n_remain < 0) { + // invalid sequence, abort + code_points.clear(); + code_points.push_back(0); + return std::make_pair(std::move(code_points), llama_partial_utf8{ 0, n_remain }); + } + + uint8_t mask = (1 << (7 - n_remain)) - 1; + value = first_byte & mask; + + ++pos; + while (*pos != 0 && n_remain > 0) { + value = (value << 6) + (static_cast<uint8_t>(*pos) & 0x3F); + ++pos; + --n_remain; + } + if (n_remain == 0) { + code_points.push_back(value); + } + } + code_points.push_back(0); + + return std::make_pair(std::move(code_points), llama_partial_utf8{ value, n_remain }); +} + +const llama_grammar_rules & llama_grammar_get_rules(const struct llama_grammar * grammar) { + return grammar->rules; +} + +llama_grammar_stacks & llama_grammar_get_stacks(struct llama_grammar * grammar) { + return grammar->stacks; +} + +// returns true iff pos points to the end of one of the definitions of a rule +static bool llama_grammar_is_end_of_sequence(const llama_grammar_element * pos) { + switch (pos->type) { + case LLAMA_GRETYPE_END: return true; // NOLINT + case LLAMA_GRETYPE_ALT: return true; // NOLINT + default: return false; + } +} + +// returns true iff chr satisfies the char range at pos (regular or inverse range) +// asserts that pos is pointing to a char range element +static std::pair<bool, const llama_grammar_element *> llama_grammar_match_char( + const llama_grammar_element * pos, + const uint32_t chr) { + + bool found = false; + bool is_positive_char = pos->type == LLAMA_GRETYPE_CHAR || pos->type == LLAMA_GRETYPE_CHAR_ANY; + + GGML_ASSERT(is_positive_char || pos->type == LLAMA_GRETYPE_CHAR_NOT); // NOLINT + + do { + if (pos[1].type == LLAMA_GRETYPE_CHAR_RNG_UPPER) { + // inclusive range, e.g. [a-z] + found = found || (pos->value <= chr && chr <= pos[1].value); + pos += 2; + } else if (pos->type == LLAMA_GRETYPE_CHAR_ANY) { + // Any character matches "." + found = true; + pos += 1; + } else { + // exact char match, e.g. [a] or "a" + found = found || pos->value == chr; + pos += 1; + } + } while (pos->type == LLAMA_GRETYPE_CHAR_ALT); + + return std::make_pair(found == is_positive_char, pos); +} + +// returns true iff some continuation of the given partial UTF-8 sequence could satisfy the char +// range at pos (regular or inverse range) +// asserts that pos is pointing to a char range element +static bool llama_grammar_match_partial_char( + const llama_grammar_element * pos, + const llama_partial_utf8 partial_utf8) { + bool is_positive_char = pos->type == LLAMA_GRETYPE_CHAR || pos->type == LLAMA_GRETYPE_CHAR_ANY; + GGML_ASSERT(is_positive_char || pos->type == LLAMA_GRETYPE_CHAR_NOT); + + uint32_t partial_value = partial_utf8.value; + int n_remain = partial_utf8.n_remain; + + // invalid sequence or 7-bit char split across 2 bytes (overlong) + if (n_remain < 0 || (n_remain == 1 && partial_value < 2)) { + return false; + } + + // range of possible code points this partial UTF-8 sequence could complete to + uint32_t low = partial_value << (n_remain * 6); + uint32_t high = low | ((1 << (n_remain * 6)) - 1); + + if (low == 0) { + if (n_remain == 2) { + low = 1 << 11; + } else if (n_remain == 3) { + low = 1 << 16; + } + } + + do { + if (pos[1].type == LLAMA_GRETYPE_CHAR_RNG_UPPER) { + // inclusive range, e.g. [a-z] + if (pos->value <= high && low <= pos[1].value) { + return is_positive_char; + } + pos += 2; + } else if (pos->type == LLAMA_GRETYPE_CHAR_ANY) { + // Any character matches "." + return true; + } else { + // exact char match, e.g. [a] or "a" + if (low <= pos->value && pos->value <= high) { + return is_positive_char; + } + pos += 1; + } + } while (pos->type == LLAMA_GRETYPE_CHAR_ALT); + + return !is_positive_char; +} + +// transforms a grammar pushdown stack into N possible stacks, all ending +// at a character range (terminal element) +static void llama_grammar_advance_stack( + const llama_grammar_rules & rules, + const llama_grammar_stack & stack, + llama_grammar_stacks & new_stacks) { + if (stack.empty()) { + if (std::find(new_stacks.begin(), new_stacks.end(), stack) == new_stacks.end()) { + new_stacks.emplace_back(stack); + } + return; + } + + const llama_grammar_element * pos = stack.back(); + + switch (pos->type) { + case LLAMA_GRETYPE_RULE_REF: { + const size_t rule_id = static_cast<size_t>(pos->value); + const llama_grammar_element * subpos = rules[rule_id].data(); + do { + // init new stack without the top (pos) + llama_grammar_stack new_stack(stack.begin(), stack.end() - 1); + if (!llama_grammar_is_end_of_sequence(pos + 1)) { + // if this rule ref is followed by another element, add that to stack + new_stack.push_back(pos + 1); + } + if (!llama_grammar_is_end_of_sequence(subpos)) { + // if alternate is nonempty, add to stack + new_stack.push_back(subpos); + } + llama_grammar_advance_stack(rules, new_stack, new_stacks); + while (!llama_grammar_is_end_of_sequence(subpos)) { + // scan to end of alternate def + subpos++; + } + if (subpos->type == LLAMA_GRETYPE_ALT) { + // there's another alternate def of this rule to process + subpos++; + } else { + break; + } + } while (true); + break; + } + case LLAMA_GRETYPE_CHAR: + case LLAMA_GRETYPE_CHAR_NOT: + case LLAMA_GRETYPE_CHAR_ANY: + if (std::find(new_stacks.begin(), new_stacks.end(), stack) == new_stacks.end()) { + // only add the stack if it's not a duplicate of one we already have + new_stacks.emplace_back(stack); + } + break; + default: + // end of alternate (LLAMA_GRETYPE_END, LLAMA_GRETYPE_ALT) or middle of char range + // (LLAMA_GRETYPE_CHAR_ALT, LLAMA_GRETYPE_CHAR_RNG_UPPER); stack should never be left on + // those + GGML_ASSERT(false); + } +} + +// takes a set of possible pushdown stacks on a grammar, which are required to +// be positioned at a character range (see `llama_grammar_advance_stack`), and +// produces the N possible stacks if the given char is accepted at those +// positions +void llama_grammar_accept( + const llama_grammar_rules & rules, + const llama_grammar_stacks & stacks, + const uint32_t chr, + llama_grammar_stacks & new_stacks) { + new_stacks.clear(); + + for (const auto & stack : stacks) { + if (stack.empty()) { + continue; + } + + auto match = llama_grammar_match_char(stack.back(), chr); + if (match.first) { + const llama_grammar_element * pos = match.second; + + // update top of stack to next element, if any + llama_grammar_stack new_stack(stack.begin(), stack.end() - 1); + if (!llama_grammar_is_end_of_sequence(pos)) { + new_stack.push_back(pos); + } + llama_grammar_advance_stack(rules, new_stack, new_stacks); + } + } +} + +static llama_grammar_candidates llama_grammar_reject_candidates( + const llama_grammar_rules & rules, + const llama_grammar_stacks & stacks, + const llama_grammar_candidates & candidates) { + GGML_ASSERT(!stacks.empty()); // REVIEW + + if (candidates.empty()) { + return {}; + } + + auto rejects = llama_grammar_reject_candidates_for_stack(rules, stacks.front(), candidates); + + for (size_t i = 1, size = stacks.size(); i < size; ++i) { + rejects = llama_grammar_reject_candidates_for_stack(rules, stacks[i], rejects); + } + return rejects; +} + +llama_grammar_candidates llama_grammar_reject_candidates_for_stack( + const llama_grammar_rules & rules, + const llama_grammar_stack & stack, + const llama_grammar_candidates & candidates) { + + llama_grammar_candidates rejects; + rejects.reserve(candidates.size()); + + if (stack.empty()) { + for (const auto & tok : candidates) { + if (*tok.code_points != 0 || tok.partial_utf8.n_remain != 0) { + rejects.push_back(tok); + } + } + return rejects; + } + + const llama_grammar_element * stack_pos = stack.back(); + + llama_grammar_candidates next_candidates; + next_candidates.reserve(candidates.size()); + + for (const auto & tok : candidates) { + if (*tok.code_points == 0) { + // reached end of full codepoints in token, reject iff it ended in a partial sequence + // that cannot satisfy this position in grammar + if (tok.partial_utf8.n_remain != 0 && + !llama_grammar_match_partial_char(stack_pos, tok.partial_utf8)) { + rejects.push_back(tok); + } + } else if (llama_grammar_match_char(stack_pos, *tok.code_points).first) { + next_candidates.push_back({ tok.index, tok.code_points + 1, tok.partial_utf8 }); + } else { + rejects.push_back(tok); + } + } + + const auto * stack_pos_after = llama_grammar_match_char(stack_pos, 0).second; + + // update top of stack to next element, if any + llama_grammar_stack stack_after(stack.begin(), stack.end() - 1); + if (!llama_grammar_is_end_of_sequence(stack_pos_after)) { + stack_after.push_back(stack_pos_after); + } + llama_grammar_stacks next_stacks; + llama_grammar_advance_stack(rules, stack_after, next_stacks); + + auto next_rejects = llama_grammar_reject_candidates(rules, next_stacks, next_candidates); + for (const auto & tok : next_rejects) { + rejects.push_back({ tok.index, tok.code_points - 1, tok.partial_utf8 }); + } + + return rejects; +} + +static bool llama_grammar_detect_left_recursion( + const llama_grammar_rules & rules, + size_t rule_index, + std::vector<bool> * rules_visited, + std::vector<bool> * rules_in_progress, + std::vector<bool> * rules_may_be_empty) { + if ((*rules_in_progress)[rule_index]) { + return true; + } + + (*rules_in_progress)[rule_index] = true; + + const llama_grammar_rule & rule = rules[rule_index]; + + // First check if the rule might produce the empty string. This could be done combined with the second + // step but it's more readable as two steps. + bool at_rule_start = true; + for (size_t i = 0; i < rule.size(); i++) { + if (llama_grammar_is_end_of_sequence(&rule[i])) { + if (at_rule_start) { + (*rules_may_be_empty)[rule_index] = true; + break; + } + at_rule_start = true; + } else { + at_rule_start = false; + } + } + + // Second, recurse into leftmost nonterminals (or next-leftmost as long as the previous nonterminal may + // be empty) + bool recurse_into_nonterminal = true; + for (size_t i = 0; i < rule.size(); i++) { + if (rule[i].type == LLAMA_GRETYPE_RULE_REF && recurse_into_nonterminal) { + if (llama_grammar_detect_left_recursion(rules, (size_t)rule[i].value, rules_visited, rules_in_progress, rules_may_be_empty)) { + return true; + } + if (!((*rules_may_be_empty)[(size_t)rule[i].value])) { + recurse_into_nonterminal = false; + } + } else if (llama_grammar_is_end_of_sequence(&rule[i])) { + recurse_into_nonterminal = true; + } else { + recurse_into_nonterminal = false; + } + } + + (*rules_in_progress)[rule_index] = false; + (*rules_visited)[rule_index] = true; + return false; +} + +// +// grammar - external +// + +struct llama_grammar * llama_grammar_init_impl( + const llama_grammar_element ** rules, + size_t n_rules, + size_t start_rule_index) { + const llama_grammar_element * pos; + + // copy rule definitions into vectors + llama_grammar_rules vec_rules(n_rules); + for (size_t i = 0; i < n_rules; i++) { + for (pos = rules[i]; pos->type != LLAMA_GRETYPE_END; pos++) { + vec_rules[i].push_back(*pos); + } + vec_rules[i].push_back({LLAMA_GRETYPE_END, 0}); + } + + // Check for left recursion + std::vector<bool> rules_visited(n_rules); + std::vector<bool> rules_in_progress(n_rules); + std::vector<bool> rules_may_be_empty(n_rules); + for (size_t i = 0; i < n_rules; i++) { + if (rules_visited[i]) { + continue; + } + if (llama_grammar_detect_left_recursion(vec_rules, i, &rules_visited, &rules_in_progress, &rules_may_be_empty)) { + LLAMA_LOG_ERROR("unsupported grammar, left recursion detected for nonterminal at index %zu", i); + return nullptr; + } + } + + // loop over alternates of start rule to build initial stacks + llama_grammar_stacks stacks; + pos = vec_rules[start_rule_index].data(); + do { + llama_grammar_stack stack; + if (!llama_grammar_is_end_of_sequence(pos)) { + // if alternate is nonempty, add to stack + stack.push_back(pos); + } + llama_grammar_advance_stack(vec_rules, stack, stacks); + while (!llama_grammar_is_end_of_sequence(pos)) { + // scan to end of alternate def + pos++; + } + if (pos->type == LLAMA_GRETYPE_ALT) { + // there's another alternate def of this rule to process + pos++; + } else { + break; + } + } while (true); + + // Important: vec_rules has to be moved here, not copied, because stacks contains + // pointers to elements of vec_rules. If vec_rules were copied into llama_grammar + // then the pointers would be invalidated when the local vec_rules goes out of scope. + return new llama_grammar{ std::move(vec_rules), std::move(stacks), {} }; +} + +void llama_grammar_free_impl(struct llama_grammar * grammar) { + delete grammar; +} + +struct llama_grammar * llama_grammar_copy_impl(const struct llama_grammar * grammar) { + llama_grammar * result = new llama_grammar{ grammar->rules, grammar->stacks, grammar->partial_utf8 }; + + // redirect elements in stacks to point to new rules + for (size_t is = 0; is < result->stacks.size(); is++) { + for (size_t ie = 0; ie < result->stacks[is].size(); ie++) { + for (size_t ir0 = 0; ir0 < grammar->rules.size(); ir0++) { + for (size_t ir1 = 0; ir1 < grammar->rules[ir0].size(); ir1++) { + if (grammar->stacks[is][ie] == &grammar->rules[ir0][ir1]) { + result->stacks[is][ie] = &result->rules[ir0][ir1]; + } + } + } + } + } + + return result; +} + +void llama_grammar_sample_impl(const struct llama_grammar * grammar, const struct llama_vocab * vocab, const struct llama_sampling * smpl, llama_token_data_array * candidates) { + GGML_ASSERT(grammar); + GGML_ASSERT(vocab); + + int64_t t_start_sample_us = ggml_time_us(); + + bool allow_eog = false; + for (const auto & stack : grammar->stacks) { + if (stack.empty()) { + allow_eog = true; + break; + } + } + + std::vector<std::pair<std::vector<uint32_t>, llama_partial_utf8>> candidates_decoded; + candidates_decoded.reserve(candidates->size); + + llama_grammar_candidates candidates_grammar; + candidates_grammar.reserve(candidates->size); + + for (size_t i = 0; i < candidates->size; ++i) { + const llama_token id = candidates->data[i].id; + const std::string & piece = vocab->cache_token_to_piece.at(id); + + if (llama_token_is_eog_impl(*vocab, id)) { + if (!allow_eog) { + candidates->data[i].logit = -INFINITY; + } + } else if (piece.empty() || piece[0] == 0) { + candidates->data[i].logit = -INFINITY; + } else { + candidates_decoded.push_back(decode_utf8(piece, grammar->partial_utf8)); + candidates_grammar.push_back({ i, candidates_decoded.back().first.data(), candidates_decoded.back().second }); + } + } + + const auto rejects = llama_grammar_reject_candidates(grammar->rules, grammar->stacks, candidates_grammar); + for (const auto & reject : rejects) { + candidates->data[reject.index].logit = -INFINITY; + } + + smpl->t_sample_us += ggml_time_us() - t_start_sample_us; +} + +void llama_grammar_accept_token_impl(struct llama_grammar * grammar, const struct llama_vocab * vocab, const struct llama_sampling * smpl, llama_token token) { + const int64_t t_start_sample_us = ggml_time_us(); + + if (llama_token_is_eog_impl(*vocab, token)) { + for (const auto & stack : grammar->stacks) { + if (stack.empty()) { + return; + } + } + GGML_ASSERT(false); + } + + const std::string & piece = vocab->cache_token_to_piece.at(token); + + // Note terminating 0 in decoded string + const auto decoded = decode_utf8(piece, grammar->partial_utf8); + const auto & code_points = decoded.first; + + llama_grammar_stacks tmp_new_stacks; + for (auto it = code_points.begin(), end = code_points.end() - 1; it != end; ++it) { + llama_grammar_accept(grammar->rules, grammar->stacks, *it, tmp_new_stacks); + grammar->stacks = tmp_new_stacks; + } + + grammar->partial_utf8 = decoded.second; + GGML_ASSERT(!grammar->stacks.empty()); + + smpl->t_sample_us += ggml_time_us() - t_start_sample_us; +} |