runner: add sync between computeBatch and completion

harmony/harmonyparser.go

@@ -47,12 +47,13 @@ func (s harmonyParserState) String() string {
 }
 
 type HarmonyParser struct {
-	state           harmonyParserState
-	MessageStartTag string
-	MessageEndTag   string
-	HeaderEndTag    string
-	acc             strings.Builder
-	lifetimeAcc     strings.Builder
+	state              harmonyParserState
+	MessageStartTag    string
+	MessageEndTag      string
+	HeaderEndTag       string
+	constraintsAllowed bool
+	acc                strings.Builder
+	lifetimeAcc        strings.Builder
 }
 
 type HarmonyEvent interface {
@@ -89,6 +90,10 @@ func (s *HarmonyParser) AddImplicitStart() {
 	s.acc.WriteString("<|start|>assistant")
 }
 
+func (s *HarmonyParser) ConstraintsAllowed() bool {
+	return s.constraintsAllowed
+}
+
 func Prefill(lastMessage api.Message) string {
 	if lastMessage.Role != "assistant" {
 		return ""
@@ -341,6 +346,7 @@ func (h *HarmonyMessageHandler) AddContent(content string) (string, string, stri
 				}
 			case "final":
 				h.state = harmonyMessageState_Normal
+				h.HarmonyParser.constraintsAllowed = true
 			}
 		case HarmonyEventContentEmitted:
 			logutil.Trace("harmony event content", "content", event.Content, "state", h.state)

parser/token_parser.go

@@ -33,6 +33,7 @@ type MessageHandler interface {
 
 type ParserInternals interface {
 	AddImplicitStartOrPrefill(prefillString string)
+	ConstraintsAllowed() bool
 }
 
 type ToolParser interface {
@@ -51,6 +52,10 @@ type defaultEngine struct{}
 
 func (defaultEngine) AddImplicitStartOrPrefill(prefillString string) {}
 
+func (defaultEngine) ConstraintsAllowed() bool {
+	return true
+}
+
 type defaultToolParser struct{}
 
 func (defaultToolParser) Add(token string) {}
@@ -104,6 +109,10 @@ func (p *TokenParser) repeatLimitReached(token string) bool {
 	return p.tokenRepeat >= p.repeatLimit
 }
 
+func (p *TokenParser) ConstraintsAllowed() bool {
+	return p.parserEngine.ConstraintsAllowed()
+}
+
 // TODO: update to work with multiple toolcalls - unmarshalling should also happen on parser level
 func (p *TokenParser) Drain() []api.ToolCall {
 	toolName, toolContent := p.toolParser.Drain()

runner/ollamarunner/runner.go

@@ -62,6 +62,11 @@ type Sequence struct {
 	// tokens that have been generated but not returned yet (e.g. for stop sequences)
 	pendingResponses []string
 
+	// startGate
+	startGate *sync.Mutex
+
+	grammarReady bool
+
 	// input cache being used by this sequence
 	cache *InputCacheSlot
 
@@ -164,6 +169,7 @@ func (s *Server) NewSequence(prompt string, images []llm.ImageData, params NewSe
 
 	// TODO(jessegross): Ingest cached history for grammar
 
+	startGate := &sync.Mutex{}
 	return &Sequence{
 		ctxs:                ctxs,
 		mmStore:             mmStore,
@@ -179,6 +185,8 @@ func (s *Server) NewSequence(prompt string, images []llm.ImageData, params NewSe
 		embeddingOnly:       params.embedding,
 		stop:                params.stop,
 		numKeep:             params.numKeep,
+		startGate:           startGate,
+		grammarReady:        false,
 	}, nil
 }
 
@@ -707,11 +715,18 @@ func (s *Server) computeBatch(activeBatch batchState) {
 		// sample a token
 		vocabSize := len(outputs) / len(activeBatch.batch.Outputs)
 		logutil.Trace("computeBatch: vocab details", "batchID", activeBatch.id, "seqIdx", i, "len(logits)", len(outputs), "len(activeBatch.batch.Outputs)", len(activeBatch.batch.Outputs), "vocabSize", vocabSize, "iBatches", iBatches)
+
+		if !seq.grammarReady {
+			seq.startGate.Lock()
+		}
 		token, err := seq.sampler.Sample(outputs[iBatches[i]*vocabSize : (iBatches[i]+1)*vocabSize])
 		if err != nil {
 			s.hardErrCh <- fmt.Errorf("failed to sample token: %w", err)
 			return
 		}
+		if !seq.grammarReady {
+			seq.startGate.Unlock()
+		}
 
 		nextBatchTokens[i].Token = token
 
@@ -782,8 +797,6 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	tokenParser := parser.NewTokenParser(req.ParserType, req.PrefillString)
-
 	if req.Options == nil {
 		opts := api.DefaultOptions()
 		req.Options = &opts
@@ -816,7 +829,7 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 		req.Options.TopP,
 		req.Options.MinP,
 		req.Options.Seed,
-		grammar,
+		nil,
 	)
 
 	seq, err := s.NewSequence(req.Prompt, req.Images, NewSequenceParams{
@@ -831,6 +844,12 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	tokenParser := parser.NewTokenParser(req.ParserType, req.PrefillString)
+	// this accounts for the default case and also the case where there is a prefill which moves the state of the parser to allow for constraints
+	if tokenParser.ConstraintsAllowed() {
+		seq.grammarReady = true
+	}
+
 	// Ensure there is a place to put the sequence, released when removed from s.seqs
 	if err := s.seqsSem.Acquire(r.Context(), 1); err != nil {
 		if errors.Is(err, context.Canceled) {
@@ -874,6 +893,9 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 			return
 		case content, ok := <-seq.responses:
 			if ok {
+				if !seq.grammarReady {
+					seq.startGate.Lock()
+				}
 				var thinking string
 				var err error
 				content, thinking, err = tokenParser.AddContent(content)
@@ -883,6 +905,13 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 					return
 				}
 
+				// only apply the grammar once
+				if tokenParser.ConstraintsAllowed() && !seq.grammarReady {
+					seq.sampler.SetGrammar(grammar, &s.mu)
+					seq.grammarReady = true
+					seq.startGate.Unlock()
+				}
+
 				if err := json.NewEncoder(w).Encode(&llm.CompletionResponse{
 					Content:  content,
 					Thinking: thinking,
@@ -909,6 +938,9 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 
 				return
 			}
+			if !seq.grammarReady {
+				seq.startGate.Unlock()
+			}
 		}
 	}
 }

sample/samplers.go

@@ -5,6 +5,7 @@ import (
 	"math"
 	"math/rand/v2"
 	"slices"
+	"sync"
 
 	"github.com/ollama/ollama/llama"
 	"github.com/ollama/ollama/model"
@@ -25,6 +26,12 @@ type Sampler struct {
 	grammar     *GrammarSampler
 }
 
+func (s *Sampler) SetGrammar(grammar *GrammarSampler, mutex *sync.Mutex) {
+	mutex.Lock()
+	defer mutex.Unlock()
+	s.grammar = grammar
+}
+
 func (s *Sampler) Sample(logits []float32) (int32, error) {
 	if len(logits) == 0 {
 		return -1, errors.New("sample: no logits provided to sample")