ggml: Use assigned layers when reporting loading stats

Reporting params.NumGPULayers can be misleading because it is the
requested number of layers, not the actual number that is loaded.
While they are often the same, there are cases where they might mismatch,
such as if the GPU backend is missing.

Author: jessegross

ml/backend/ggml/ggml.go

@@ -356,23 +356,25 @@ func New(modelPath string, params ml.BackendParams) (ml.Backend, error) {
 	}
 
 	// Mimic llama runner logs summarizing layers and memory
-	slog.Info(fmt.Sprintf("offloading %d repeating layers to GPU", max(0, params.NumGPULayers-1)))
 	gpuLayers := 0
+	for _, layer := range layers {
+		if C.ggml_backend_dev_type(layer.d) == C.GGML_BACKEND_DEVICE_TYPE_GPU {
+			gpuLayers++
+		}
+	}
+	slog.Info(fmt.Sprintf("offloading %d repeating layers to GPU", gpuLayers))
+
 	switch C.ggml_backend_dev_type(output.d) {
-	case 0: // CPU
+	case C.GGML_BACKEND_DEVICE_TYPE_CPU:
 		slog.Info("offloading output layer to CPU")
-	case 1: // GPU
+	case C.GGML_BACKEND_DEVICE_TYPE_GPU:
 		slog.Info("offloading output layer to GPU")
 		gpuLayers++
-	case 2: // ACCEL
+	case C.GGML_BACKEND_DEVICE_TYPE_ACCEL:
 		slog.Info("offloading output layer to ACCEL")
 	}
-	for _, layer := range layers {
-		if C.ggml_backend_dev_type(layer.d) == 1 {
-			gpuLayers++
-		}
-	}
 	slog.Info(fmt.Sprintf("offloaded %d/%d layers to GPU", gpuLayers, len(layers)+1))
+
 	for bs := range maps.Values(bbs) {
 		slog.Info("model weights", "buffer", C.GoString(C.ggml_backend_buffer_name(bs)), "size", format.HumanBytes2(uint64(C.ggml_backend_buffer_get_size(bs))))
 	}