<!--Copyright 2024 The HuggingFace Team. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
specific language governing permissions and limitations under the License.

⚠️ Note that this file is in Markdown but contain specific syntax for our doc-builder (similar to MDX) that may not be
rendered properly in your Markdown viewer.

-->

# AWQ

[Activation-aware Weight Quantization (AWQ)](https://hf.co/papers/2306.00978) preserves a small fraction of the weights that are important for LLM performance to compress a model to 4-bits with minimal performance degradation.

There are several libraries for quantizing models with the AWQ algorithm, such as [llm-awq](https://github.com/mit-han-lab/llm-awq), [autoawq](https://github.com/casper-hansen/AutoAWQ) or [optimum-intel](https://huggingface.co/docs/optimum/main/en/intel/optimization_inc). Transformers supports loading models quantized with the llm-awq and autoawq libraries. This guide will show you how to load models quantized with autoawq, but the process is similar for llm-awq quantized models.

Run the command below to install autoawq

```bash
pip install autoawq
```

> [!WARNING]
> AutoAWQ downgrades Transformers to version 4.47.1. If you want to do inference with AutoAWQ, you may need to reinstall your Transformers' version after installing AutoAWQ.

Identify an AWQ-quantized model by checking the `quant_method` key in the models [config.json](https://huggingface.co/TheBloke/zephyr-7B-alpha-AWQ/blob/main/config.json) file.

```json
{
  "_name_or_path": "/workspace/process/huggingfaceh4_zephyr-7b-alpha/source",
  "architectures": [
    "MistralForCausalLM"
  ],
  ...
  ...
  ...
  "quantization_config": {
    "quant_method": "awq",
    "zero_point": true,
    "group_size": 128,
    "bits": 4,
    "version": "gemm"
  }
}
```

Load the AWQ-quantized model with [`~PreTrainedModel.from_pretrained`]. This automatically sets the other weights to fp16 by default for performance reasons. Use the `dtype` parameter to load these other weights in a different format.

If the model is loaded on the CPU, use the `device_map` parameter to move it to an accelerator.

```py
from transformers import AutoModelForCausalLM, AutoTokenizer
from accelerate import Accelerator
import torch

device = Accelerator().device

model = AutoModelForCausalLM.from_pretrained(
  "TheBloke/zephyr-7B-alpha-AWQ",
  dtype=torch.float32,
  device_map=device
)
```

Use `attn_implementation` to enable [FlashAttention2](../perf_infer_gpu_one#flashattention-2) to further accelerate inference.

```py
from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained(
  "TheBloke/zephyr-7B-alpha-AWQ",
  attn_implementation="flash_attention_2",
  device_map="cuda:0"
)
```

## Fused modules

Fused modules offer improved accuracy and performance. They are supported out-of-the-box for AWQ modules for [Llama](https://huggingface.co/meta-llama) and [Mistral](https://huggingface.co/mistralai/Mistral-7B-v0.1) architectures, but you can also fuse AWQ modules for unsupported architectures.

> [!WARNING]
> Fused modules cannot be combined with other optimization techniques such as FlashAttention2.

<hfoptions id="fuse">
<hfoption id="supported architectures">

Create an [`AwqConfig`] and set the parameters `fuse_max_seq_len` and `do_fuse=True` to enable fused modules. The `fuse_max_seq_len` parameter is the total sequence length and it should include the context length and the expected generation length. Set it to a larger value to be safe.

The example below fuses the AWQ modules of the [TheBloke/Mistral-7B-OpenOrca-AWQ](https://huggingface.co/TheBloke/Mistral-7B-OpenOrca-AWQ) model.

```python
import torch
from transformers import AwqConfig, AutoModelForCausalLM

quantization_config = AwqConfig(
    bits=4,
    fuse_max_seq_len=512,
    do_fuse=True,
)
model = AutoModelForCausalLM.from_pretrained(
  "TheBloke/Mistral-7B-OpenOrca-AWQ",
  quantization_config=quantization_config
).to(0)
```

The [TheBloke/Mistral-7B-OpenOrca-AWQ](https://huggingface.co/TheBloke/Mistral-7B-OpenOrca-AWQ) model was benchmarked with `batch_size=1` with and without fused modules.

<figcaption class="text-center text-gray-500 text-lg">Unfused module</figcaption>

|   Batch Size |   Prefill Length |   Decode Length |   Prefill tokens/s |   Decode tokens/s | Memory (VRAM)   |
|-------------:|-----------------:|----------------:|-------------------:|------------------:|:----------------|
|            1 |               32 |              32 |            60.0984 |           38.4537 | 4.50 GB (5.68%) |
|            1 |               64 |              64 |          1333.67   |           31.6604 | 4.50 GB (5.68%) |
|            1 |              128 |             128 |          2434.06   |           31.6272 | 4.50 GB (5.68%) |
|            1 |              256 |             256 |          3072.26   |           38.1731 | 4.50 GB (5.68%) |
|            1 |              512 |             512 |          3184.74   |           31.6819 | 4.59 GB (5.80%) |
|            1 |             1024 |            1024 |          3148.18   |           36.8031 | 4.81 GB (6.07%) |
|            1 |             2048 |            2048 |          2927.33   |           35.2676 | 5.73 GB (7.23%) |

<figcaption class="text-center text-gray-500 text-lg">Fused module</figcaption>

|   Batch Size |   Prefill Length |   Decode Length |   Prefill tokens/s |   Decode tokens/s | Memory (VRAM)   |
|-------------:|-----------------:|----------------:|-------------------:|------------------:|:----------------|
|            1 |               32 |              32 |            81.4899 |           80.2569 | 4.00 GB (5.05%) |
|            1 |               64 |              64 |          1756.1    |          106.26   | 4.00 GB (5.05%) |
|            1 |              128 |             128 |          2479.32   |          105.631  | 4.00 GB (5.06%) |
|            1 |              256 |             256 |          1813.6    |           85.7485 | 4.01 GB (5.06%) |
|            1 |              512 |             512 |          2848.9    |           97.701  | 4.11 GB (5.19%) |
|            1 |             1024 |            1024 |          3044.35   |           87.7323 | 4.41 GB (5.57%) |
|            1 |             2048 |            2048 |          2715.11   |           89.4709 | 5.57 GB (7.04%) |

The speed and throughput of fused and unfused modules were also tested with the [optimum-benchmark](https://github.com/huggingface/optimum-benchmark) library.

<div class="flex gap-4">
  <div>
    <img class="rounded-xl" src="https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/quantization/fused_forward_memory_plot.png" alt="generate throughput per batch size" />
    <figcaption class="mt-2 text-center text-sm text-gray-500">forward peak memory/batch size</figcaption>
  </div>
  <div>
    <img class="rounded-xl" src="https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/quantization/fused_generate_throughput_plot.png" alt="forward latency per batch size" />
    <figcaption class="mt-2 text-center text-sm text-gray-500">generate throughput/batch size</figcaption>
  </div>
</div>

</hfoption>
<hfoption id="unsupported architectures">

For architectures that don't support fused modules, create an [`AwqConfig`] and define a custom fusing mapping in `modules_to_fuse` to determine which modules need to be fused.

The example below fuses the AWQ modules of the [TheBloke/Yi-34B-AWQ](https://huggingface.co/TheBloke/Yi-34B-AWQ) model.

```python
import torch
from transformers import AwqConfig, AutoModelForCausalLM

quantization_config = AwqConfig(
    bits=4,
    fuse_max_seq_len=512,
    modules_to_fuse={
        "attention": ["q_proj", "k_proj", "v_proj", "o_proj"],
        "layernorm": ["ln1", "ln2", "norm"],
        "mlp": ["gate_proj", "up_proj", "down_proj"],
        "use_alibi": False,
        "num_attention_heads": 56,
        "num_key_value_heads": 8,
        "hidden_size": 7168
    }
)

model = AutoModelForCausalLM.from_pretrained(
  "TheBloke/Yi-34B-AWQ",
  quantization_config=quantization_config
).to(0)
```

The parameter `modules_to_fuse` should include the following keys.

- `"attention"`: The names of the attention layers to fuse in the following order: query, key, value and output projection layer. If you don't want to fuse these layers, pass an empty list.
- `"layernorm"`: The names of all the LayerNorm layers you want to replace with a custom fused LayerNorm. If you don't want to fuse these layers, pass an empty list.
- `"mlp"`: The names of the MLP layers you want to fuse into a single MLP layer in the order: (gate (dense, layer, post-attention) / up / down layers).
- `"use_alibi"`: If your model uses ALiBi positional embedding.
- `"num_attention_heads"`: The number of attention heads.
- `"num_key_value_heads"`: The number of key value heads that should be used to implement Grouped Query Attention (GQA).

  | parameter value | attention |
  |---|---|
  | `num_key_value_heads=num_attention_heads` | Multi-Head Attention |
  | `num_key_value_heads=1` | Multi-Query Attention |
  | `num_key_value_heads=...` | Grouped Query Attention |

- `"hidden_size"`: The dimension of the hidden representations.

</hfoption>
</hfoptions>

## ExLlamaV2

[ExLlamaV2](https://github.com/turboderp/exllamav2) kernels support faster prefill and decoding. Run the command below to install the latest version of autoawq with ExLlamaV2 support.

```bash
pip install git+https://github.com/casper-hansen/AutoAWQ.git
```

Set `version="exllama"` in [`AwqConfig`] to enable ExLlamaV2 kernels.

> [!TIP]
> ExLlamaV2 is supported on AMD GPUs.

```py
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer, AwqConfig

quantization_config = AwqConfig(version="exllama")

model = AutoModelForCausalLM.from_pretrained(
    "TheBloke/Mistral-7B-Instruct-v0.1-AWQ",
    quantization_config=quantization_config,
    device_map="auto",
)
```

## Resources

Run the AWQ demo [notebook](https://colab.research.google.com/drive/1HzZH89yAXJaZgwJDhQj9LqSBux932BvY#scrollTo=Wwsg6nCwoThm) for more examples of how to quantize a model, push a quantized model to the Hub, and more.
