grammars: 1.5x faster inference w/ complex grammars (vector reserves / reuses) (#6609)

* grammars: reserve rejects & next candidates

* grammars: reuse new_stacks

* grammars: fix missing sig change in llama.h

* grammars: fix test (api changed)

* grammars: update gbnf-validator.cpp

* grammars: simpler syntax (no swap)

1 files changed, 10 insertions, 6 deletions

diff --git a/llama.cpp b/llama.cpp
index b6e2ade9..ad07059c 100644
--- a/llama.cpp
+++ b/llama.cpp
@@ -11912,12 +11912,13 @@ static void llama_grammar_advance_stack(
 // 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
-std::vector<std::vector<const llama_grammar_element *>> llama_grammar_accept(
+void llama_grammar_accept(
         const std::vector<std::vector<llama_grammar_element>>         & rules,
         const std::vector<std::vector<const llama_grammar_element *>> & stacks,
-        const uint32_t                                                  chr) {
+        const uint32_t                                                  chr,
+        std::vector<std::vector<const llama_grammar_element *>>       & new_stacks) {
 
-    std::vector<std::vector<const llama_grammar_element *>> new_stacks;
+    new_stacks.clear();
 
     for (const auto & stack : stacks) {
         if (stack.empty()) {
@@ -11936,8 +11937,6 @@ std::vector<std::vector<const llama_grammar_element *>> llama_grammar_accept(
             llama_grammar_advance_stack(rules, new_stack, new_stacks);
         }
     }
-
-    return new_stacks;
 }
 
 static std::vector<llama_grammar_candidate> llama_grammar_reject_candidates(
@@ -11951,6 +11950,7 @@ static std::vector<llama_grammar_candidate> llama_grammar_reject_candidates_for_
         const std::vector<llama_grammar_candidate>            & candidates) {
 
     std::vector<llama_grammar_candidate> rejects;
+    rejects.reserve(candidates.size());
 
     if (stack.empty()) {
         for (const auto & tok : candidates) {
@@ -11964,6 +11964,8 @@ static std::vector<llama_grammar_candidate> llama_grammar_reject_candidates_for_
     const llama_grammar_element * stack_pos = stack.back();
 
     std::vector<llama_grammar_candidate> 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
@@ -12771,8 +12773,10 @@ void llama_grammar_accept_token(struct llama_context * ctx, struct llama_grammar
     // Note terminating 0 in decoded string
     const auto   decoded     = decode_utf8(piece, grammar->partial_utf8);
     const auto & code_points = decoded.first;
+    std::vector<std::vector<const llama_grammar_element *>> tmp_new_stacks;
     for (auto it = code_points.begin(), end = code_points.end() - 1; it != end; ++it) {
-        grammar->stacks = llama_grammar_accept(grammar->rules, grammar->stacks, *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());