GGUF format and llama.cpp quantization for efficient CPU/GPU inference. Use when deploying models on consumer hardware, Apple Silicon, or when needing flexible quantization from 2-8 bit without GPU requirements.
The GGUF (GPT-Generated Unified Format) is the standard file format for llama.cpp, enabling efficient inference on CPUs, Apple Silicon, and GPUs with flexible quantization options.
When to use GGUF
Use GGUF when:
Deploying on consumer hardware (laptops, desktops)
Running on Apple Silicon (M1/M2/M3) with Metal acceleration
Need CPU inference without GPU requirements
Want flexible quantization (Q2_K to Q8_0)
Using local AI tools (LM Studio, Ollama, text-generation-webui)
Key advantages:
Universal hardware: CPU, Apple Silicon, NVIDIA, AMD support
No Python runtime: Pure C/C++ inference
Flexible quantization: 2-8 bit with various methods (K-quants)
Ecosystem support: LM Studio, Ollama, koboldcpp, and more
imatrix: Importance matrix for better low-bit quality
Use alternatives instead:
AWQ/GPTQ: Maximum accuracy with calibration on NVIDIA GPUs
HQQ: Fast calibration-free quantization for HuggingFace
bitsandbytes: Simple integration with transformers library
TensorRT-LLM: Production NVIDIA deployment with maximum speed
Quick start
Installation
# Clone llama.cpp
git clone https://github.com/ggml-org/llama.cpp
cd llama.cpp
# Build (CPU)
make
# Build with CUDA (NVIDIA)
make GGML_CUDA=1
# Build with Metal (Apple Silicon)
make GGML_METAL=1
# Install Python bindings (optional)
pip install llama-cpp-python
Convert model to GGUF
# Install requirements
pip install -r requirements.txt
# Convert HuggingFace model to GGUF (FP16)
python convert_hf_to_gguf.py ./path/to/model --outfile model-f16.gguf
# Or specify output type
python convert_hf_to_gguf.py ./path/to/model \
--outfile model-f16.gguf \
--outtype f16
Workflow 2: With importance matrix (better quality)
# 1. Convert to GGUF
python convert_hf_to_gguf.py ./model --outfile model-f16.gguf
# 2. Create calibration text (diverse samples)
cat > calibration.txt << 'EOF'
The quick brown fox jumps over the lazy dog.
Machine learning is a subset of artificial intelligence.
Python is a popular programming language.
# Add more diverse text samples...
EOF
# 3. Generate importance matrix
./llama-imatrix -m model-f16.gguf \
-f calibration.txt \
--chunk 512 \
-o model.imatrix \
-ngl 35 # GPU layers if available
# 4. Quantize with imatrix
./llama-quantize --imatrix model.imatrix \
model-f16.gguf \
model-q4_k_m.gguf \
Q4_K_M
# Build with Metal
make clean && make GGML_METAL=1
# Run with Metal acceleration
./llama-cli -m model.gguf -ngl 99 -p "Hello"
# Python with Metal
llm = Llama(
model_path="model.gguf",
n_gpu_layers=99, # Offload all layers
n_threads=1 # Metal handles parallelism
)
NVIDIA CUDA
# Build with CUDA
make clean && make GGML_CUDA=1
# Run with CUDA
./llama-cli -m model.gguf -ngl 35 -p "Hello"
# Specify GPU
CUDA_VISIBLE_DEVICES=0 ./llama-cli -m model.gguf -ngl 35
CPU optimization
# Build with AVX2/AVX512
make clean && make
# Run with optimal threads
./llama-cli -m model.gguf -t 8 -p "Hello"
# Python CPU config
llm = Llama(
model_path="model.gguf",
n_gpu_layers=0, # CPU only
n_threads=8, # Match physical cores
n_batch=512 # Batch size for prompt processing
)
Integration with tools
Ollama
# Create Modelfile
cat > Modelfile << 'EOF'
FROM ./model-q4_k_m.gguf
TEMPLATE """{{ .System }}
{{ .Prompt }}"""
PARAMETER temperature 0.7
PARAMETER num_ctx 4096
EOF
# Create Ollama model
ollama create mymodel -f Modelfile
# Run
ollama run mymodel "Hello!"
LM Studio
Place GGUF file in ~/.cache/lm-studio/models/
Open LM Studio and select the model
Configure context length and GPU offload
Start inference
text-generation-webui
# Place in models folder
cp model-q4_k_m.gguf text-generation-webui/models/
# Start with llama.cpp loader
python server.py --model model-q4_k_m.gguf --loader llama.cpp --n-gpu-layers 35
Best practices
Use K-quants: Q4_K_M offers best quality/size balance
Use imatrix: Always use importance matrix for Q4 and below
GPU offload: Offload as many layers as VRAM allows
Context length: Start with 4096, increase if needed
Thread count: Match physical CPU cores, not logical
Batch size: Increase n_batch for faster prompt processing
Common issues
Model loads slowly:
# Use mmap for faster loading
./llama-cli -m model.gguf --mmap
Out of memory:
# Reduce GPU layers
./llama-cli -m model.gguf -ngl 20 # Reduce from 35
# Or use smaller quantization
./llama-quantize model-f16.gguf model-q3_k_m.gguf Q3_K_M
Poor quality at low bits:
# Always use imatrix for Q4 and below
./llama-imatrix -m model-f16.gguf -f calibration.txt -o model.imatrix
./llama-quantize --imatrix model.imatrix model-f16.gguf model-q4_k_m.gguf Q4_K_M