Quantization docs (#911)

Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>

docs/source/_toctree.yml

@@ -21,6 +21,8 @@
 - sections:
   - local: conceptual/streaming
     title: Streaming
+  - local: conceptual/quantization
+    title: Quantization
   - local: conceptual/tensor_parallelism
     title: Tensor Parallelism
   - local: conceptual/paged_attention

docs/source/basic_tutorials/preparing_model.md

@@ -4,7 +4,7 @@ Text Generation Inference improves the model in several aspects.
 
 ## Quantization
 
-TGI supports [bits-and-bytes](https://github.com/TimDettmers/bitsandbytes#bitsandbytes) and [GPT-Q](https://arxiv.org/abs/2210.17323) quantization. To speed up inference with quantization, simply set `quantize` flag to `bitsandbytes` or `gptq` depending on the quantization technique you wish to use. When using GPT-Q quantization, you need to point to one of the models [here](https://huggingface.co/models?search=gptq).
+TGI supports [bits-and-bytes](https://github.com/TimDettmers/bitsandbytes#bitsandbytes) and [GPT-Q](https://arxiv.org/abs/2210.17323) quantization. To speed up inference with quantization, simply set `quantize` flag to `bitsandbytes` or `gptq` depending on the quantization technique you wish to use. When using GPT-Q quantization, you need to point to one of the models [here](https://huggingface.co/models?search=gptq). To get more information about quantization, please refer to (./conceptual/quantization.md)
 
 
 ## RoPE Scaling

docs/source/conceptual/quantization.md

+# Quantization
+
+TGI offers GPTQ and bits-and-bytes quantization to quantize large language models.
+
+## Quantization with GPTQ
+
+GPTQ is a post-training quantization method to make the model smaller. It quantizes the layers by finding a compressed version of that weight, that will yield a minimum mean squared error like below 👇 
+
+Given a layer \\(l\\) with weight matrix \\(W_{l}\\) and layer input \\(X_{l}\\), find quantized weight \\(\\hat{W}_{l}\\):
+
+$$({\hat{W}_{l}}^{*} = argmin_{\hat{W_{l}}} ||W_{l}X-\hat{W}_{l}X||^{2}_{2})$$
+
+
+TGI allows you to both run an already GPTQ quantized model (see available models [here](https://huggingface.co/models?search=gptq)) or quantize a model of your choice using quantization script. You can run a quantized model by simply passing --quantize like below 👇 
+
+```bash
+docker run --gpus all --shm-size 1g -p 8080:80 -v $volume:/data ghcr.io/huggingface/text-generation-inference:latest --model-id $model --quantize gptq
+```
+
+Note that TGI's GPTQ implementation doesn't use [AutoGPTQ](https://github.com/PanQiWei/AutoGPTQ) under the hood. However, models quantized using AutoGPTQ or Optimum can still be served by TGI. 
+
+To quantize a given model using GPTQ with a calibration dataset, simply run
+
+```bash
+text-generation-server quantize tiiuae/falcon-40b /data/falcon-40b-gptq
+# Add --upload-to-model-id MYUSERNAME/falcon-40b to push the created model to the hub directly
+```
+
+This will create a new directory with the quantized files which you can use with,
+
+```bash
+text-generation-launcher --model-id /data/falcon-40b-gptq/ --sharded true --num-shard 2 --quantize gptq
+```
+
+You can learn more about the quantization options by running `text-generation-server quantize --help`.
+
+If you wish to do more with GPTQ models (e.g. train an adapter on top), you can read about transformers GPTQ integration [here](https://huggingface.co/blog/gptq-integration).
+You can learn more about GPTQ from the [paper](https://arxiv.org/pdf/2210.17323.pdf).
+
+## Quantization with bitsandbytes
+
+bitsandbytes is a library used to apply 8-bit and 4-bit quantization to models. Unlike GPTQ quantization, bitsandbytes doesn't require a calibration dataset or any post-processing – weights are automatically quantized on load. However, inference with bitsandbytes is slower than GPTQ or FP16 precision.
+
+8-bit quantization enables multi-billion parameter scale models to fit in smaller hardware without degrading performance too much. 
+In TGI, you can use 8-bit quantization by adding `--quantize bitsandbytes` like below 👇
+
+```bash
+docker run --gpus all --shm-size 1g -p 8080:80 -v $volume:/data ghcr.io/huggingface/text-generation-inference:latest --model-id $model --quantize --bitsandbytes
+```
+
+4-bit quantization is also possible with bitsandbytes. You can choose one of the following 4-bit data types: 4-bit float (`fp4`), or 4-bit `NormalFloat` (`nf4`). These data types were introduced in the context of parameter-efficient fine-tuning, but you can apply them for inference by automatically converting the model weights on load.
+
+In TGI, you can use 4-bit quantization by adding `--quantize bitsandbytes-nf4` or `--quantize bitsandbytes-fp4` like below 👇 
+
+```bash
+docker run --gpus all --shm-size 1g -p 8080:80 -v $volume:/data ghcr.io/huggingface/text-generation-inference:latest --model-id $model --quantize --bitsandbytes-nf4
+```
+
+You can get more information about 8-bit quantization by reading this [blog post](https://huggingface.co/blog/hf-bitsandbytes-integration), and 4-bit quantization by reading [this blog post](https://huggingface.co/blog/4bit-transformers-bitsandbytes).