unbound max num gpu layers (#591)

---------
Co-authored-by: Michael Yang <mxyng@pm.me>

llm/ggml.go

@@ -77,6 +77,7 @@ type model interface {
 	ModelFamily() string
 	ModelType() string
 	FileType() string
+	NumLayers() int64
 }
 
 type container interface {

llm/gguf.go

@@ -195,6 +195,16 @@ func (llm *ggufModel) Decode(r io.Reader) error {
 	return nil
 }
 
+func (llm *ggufModel) NumLayers() int64 {
+	value, exists := llm.kv[fmt.Sprintf("%s.block_count", llm.ModelFamily())]
+	if !exists {
+		return 0
+	}
+
+	v := value.(uint32)
+	return int64(v)
+}
+
 func (ggufModel) readU8(r io.Reader) uint8 {
 	var u8 uint8
 	binary.Read(r, binary.LittleEndian, &u8)

llm/llama.go

@@ -152,6 +152,10 @@ func (llm *llamaModel) FileType() string {
 	return fileType(llm.hyperparameters.FileType)
 }
 
+func (llm *llamaModel) NumLayers() int64 {
+	return int64(llm.hyperparameters.NumLayer)
+}
+
 type llamaHyperparameters struct {
 	// NumVocab is the size of the model's vocabulary.
 	NumVocab uint32
@@ -207,13 +211,13 @@ func CheckVRAM() (int, error) {
 	return total, nil
 }
 
-func NumGPU(opts api.Options) int {
+func NumGPU(numLayer, fileSizeBytes int64, opts api.Options) int {
 	if opts.NumGPU != -1 {
 		return opts.NumGPU
 	}
 	n := 1 // default to enable metal on macOS
 	if runtime.GOOS == "linux" {
-		vram, err := CheckVRAM()
+		vramMib, err := CheckVRAM()
 		if err != nil {
 			if err.Error() != "nvidia-smi command failed" {
 				log.Print(err.Error())
@@ -221,33 +225,25 @@ func NumGPU(opts api.Options) int {
 			// nvidia driver not installed or no nvidia GPU found
 			return 0
 		}
-		// TODO: this is a very rough heuristic, better would be to calculate this based on number of layers and context size
-		switch {
-		case vram < 500:
-			log.Printf("WARNING: Low VRAM detected, disabling GPU")
-			n = 0
-		case vram < 1000:
-			n = 4
-		case vram < 2000:
-			n = 8
-		case vram < 4000:
-			n = 12
-		case vram < 8000:
-			n = 16
-		case vram < 12000:
-			n = 24
-		case vram < 16000:
-			n = 32
-		default:
-			n = 48
-		}
-		log.Printf("%d MB VRAM available, loading %d GPU layers", vram, n)
+
+		totalVramBytes := int64(vramMib) * 1024 * 1024 // 1 MiB = 1024^2 bytes
+
+		// Calculate bytes per layer
+		// TODO: this is a rough heuristic, better would be to calculate this based on number of layers and context size
+		bytesPerLayer := fileSizeBytes / numLayer
+
+		// set n to the max number of layers we can fit in VRAM
+		return int(totalVramBytes / bytesPerLayer)
+
+		log.Printf("%d MiB VRAM available, loading up to %d GPU layers", vramMib, n)
 	}
-	return n
+	// default to enable metal on macOS
+	return 1
 }
 
-func newLlama(model string, adapters []string, runners []ModelRunner, opts api.Options) (*llama, error) {
-	if _, err := os.Stat(model); err != nil {
+func newLlama(model string, adapters []string, runners []ModelRunner, numLayers int64, opts api.Options) (*llama, error) {
+	fileInfo, err := os.Stat(model)
+	if err != nil {
 		return nil, err
 	}
 
@@ -261,7 +257,7 @@ func newLlama(model string, adapters []string, runners []ModelRunner, opts api.O
 		"--rope-freq-base", fmt.Sprintf("%f", opts.RopeFrequencyBase),
 		"--rope-freq-scale", fmt.Sprintf("%f", opts.RopeFrequencyScale),
 		"--batch-size", fmt.Sprintf("%d", opts.NumBatch),
-		"--n-gpu-layers", fmt.Sprintf("%d", NumGPU(opts)),
+		"--n-gpu-layers", fmt.Sprintf("%d", NumGPU(numLayers, fileInfo.Size(), opts)),
 		"--embedding",
 	}
 

llm/llm.go

@@ -91,9 +91,9 @@ func New(workDir, model string, adapters []string, opts api.Options) (LLM, error
 	switch ggml.Name() {
 	case "gguf":
 		opts.NumGQA = 0 // TODO: remove this when llama.cpp runners differ enough to need separate newLlama functions
-		return newLlama(model, adapters, chooseRunners(workDir, "gguf"), opts)
+		return newLlama(model, adapters, chooseRunners(workDir, "gguf"), ggml.NumLayers(), opts)
 	case "ggml", "ggmf", "ggjt", "ggla":
-		return newLlama(model, adapters, chooseRunners(workDir, "ggml"), opts)
+		return newLlama(model, adapters, chooseRunners(workDir, "ggml"), ggml.NumLayers(), opts)
 	default:
 		return nil, fmt.Errorf("unknown ggml type: %s", ggml.ModelFamily())
 	}