ollamarunner: Separate text and multimodal graphs

For some multimodal models (such as gemma3), we create a single
graph that generates the image embedding and then use this in the
text model. The embedding tensor is completely opaque to the runner.

However, this doesn't work if we need to use the embedding in multiple
batches. This can arise if the embedding is larger than the batch size.
In these cases (as with llama4), we would like to create views that
are more appropriately sized. However, if we do this then the original
source tensor is used in multiple graphs, which isn't allowed. To
avoid that problem, models with this pattern compute the embedding
tensor on first use and recreate the individual views. There is no
longer a single vision and text graph.

This codifies the pattern of separating vision and text graphs. The
logic of computing tensors on demand is moved to the runner, so models
no longer have to worry about this. It also gives the runner visibility
into the multimodal tensors, which is important for memory management.

runner/ollamarunner/runner.go

@@ -40,6 +40,9 @@ type Sequence struct {
 	// multimodal embeddings
 	ctxs []ml.Context
 
+	// mmStore holds multimodal embeddings to mange memory and enable splitting across batches
+	mmStore multimodalStore
+
 	// batch index
 	iBatch int
 
@@ -101,7 +104,7 @@ func (s *Server) NewSequence(prompt string, images []llm.ImageData, params NewSe
 
 	startTime := time.Now()
 
-	inputs, ctxs, err := s.inputs(prompt, images)
+	inputs, ctxs, mmStore, err := s.inputs(prompt, images)
 	if err != nil {
 		return nil, fmt.Errorf("failed to process inputs: %w", err)
 	} else if len(inputs) == 0 {
@@ -156,6 +159,7 @@ func (s *Server) NewSequence(prompt string, images []llm.ImageData, params NewSe
 
 	return &Sequence{
 		ctxs:                ctxs,
+		mmStore:             mmStore,
 		inputs:              inputs,
 		numPromptInputs:     len(inputs),
 		startProcessingTime: startTime,
@@ -174,9 +178,10 @@ func (s *Server) NewSequence(prompt string, images []llm.ImageData, params NewSe
 // inputs processes the prompt and images into a list of inputs
 // by splitting the prompt on [img-<n>] tags, tokenizing text and
 // decoding images
-func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, []ml.Context, error) {
+func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, []ml.Context, multimodalStore, error) {
 	var inputs []input.Input
 	var ctxs []ml.Context
+	var mmStore multimodalStore
 
 	var parts []string
 	var matches [][]string
@@ -187,6 +192,7 @@ func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, [
 		re := regexp.MustCompile(`\[img-(\d+)\]`)
 		parts = re.Split(prompt, -1)
 		matches = re.FindAllStringSubmatch(prompt, -1)
+		mmStore = newMultimodalStore()
 	} else {
 		parts = []string{prompt}
 	}
@@ -196,7 +202,7 @@ func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, [
 		// text - tokenize
 		tokens, err := s.model.(model.TextProcessor).Encode(part, i == 0)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, nil, err
 		}
 
 		for _, t := range tokens {
@@ -216,7 +222,7 @@ func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, [
 			}
 
 			if imageIndex < 0 {
-				return nil, nil, fmt.Errorf("invalid image index: %d", n)
+				return nil, nil, nil, fmt.Errorf("invalid image index: %d", n)
 			}
 
 			ctx := s.model.Backend().NewContext()
@@ -224,13 +230,15 @@ func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, [
 			ctxs = append(ctxs, ctx)
 			imageEmbeddings, err := multimodalProcessor.EncodeMultimodal(ctx, images[imageIndex].Data)
 			if err != nil {
-				return nil, nil, err
+				return nil, nil, nil, err
 			}
 
 			s.multimodalHash.Reset()
 			_, _ = s.multimodalHash.Write(images[imageIndex].Data)
 			imageHash := s.multimodalHash.Sum64()
 
+			mmStore.addMultimodal(imageEmbeddings)
+
 			inputs = append(inputs, input.Input{Multimodal: imageEmbeddings, MultimodalHash: imageHash})
 			postTokenize = true
 		}
@@ -240,11 +248,11 @@ func (s *Server) inputs(prompt string, images []llm.ImageData) ([]input.Input, [
 		var err error
 		inputs, err = multimodalProcessor.PostTokenize(inputs)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, nil, err
 		}
 	}
 
-	return inputs, ctxs, nil
+	return inputs, ctxs, mmStore, nil
 }
 
 type Server struct {
@@ -363,6 +371,9 @@ func (s *Server) processBatch() error {
 	}
 	defer s.mu.Unlock()
 
+	ctx := s.model.Backend().NewContext()
+	defer ctx.Close()
+
 	var batchInputs []int32
 	var batch input.Batch
 
@@ -433,7 +444,11 @@ func (s *Server) processBatch() error {
 
 			batchInputs = append(batchInputs, inp.Token)
 			if inp.Multimodal != nil {
-				batch.Multimodal = append(batch.Multimodal, input.MultimodalIndex{Index: len(batchInputs) - 1, Multimodal: inp.Multimodal})
+				mm, err := seq.mmStore.getMultimodal(s.model.Backend(), ctx, inp.Multimodal)
+				if err != nil {
+					return err
+				}
+				batch.Multimodal = append(batch.Multimodal, input.MultimodalIndex{Index: len(batchInputs) - 1, Multimodal: mm})
 			}
 
 			batch.Positions = append(batch.Positions, int32(len(seq.cache.Inputs)+len(seq.pendingInputs)))
@@ -459,9 +474,6 @@ func (s *Server) processBatch() error {
 		return nil
 	}
 
-	ctx := s.model.Backend().NewContext()
-	defer ctx.Close()
-
 	modelOutput, err := model.Forward(ctx, s.model, batchInputs, batch)
 	if err != nil {
 		return fmt.Errorf("failed to decode batch: %w", err)