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Add inc fp8 qunatization documentation (#635)
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.. _INC: | ||
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FP8 INC | ||
======= | ||
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vLLM supports FP8 (8-bit floating point) weight and activation quantization using Intel® Neural Compressor (INC) on Intel® Gaudi® 2 and Intel® Gaudi® 3 AI accelerators. | ||
Currently, quantization is validated only in Llama models. | ||
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Intel Gaudi supports quantization of various modules and functions, including, but not limited to ``Linear``, ``KVCache``, ``Matmul`` and ``Softmax``. For more information, please refer to: | ||
`Supported Modules\\Supported Functions\\Custom Patched Modules <https://docs.habana.ai/en/latest/PyTorch/Inference_on_PyTorch/Quantization/Inference_Using_FP8.html#supported-modules>`_. | ||
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.. note:: | ||
Measurement files are required to run quantized models with vLLM on Gaudi accelerators. The FP8 model calibration procedure is described in the `vllm-hpu-extention <https://github.com/HabanaAI/vllm-hpu-extension/tree/main/calibration/README.md>`_ package. | ||
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.. note:: | ||
``QUANT_CONFIG`` is an environment variable that points to the measurement or quantization `JSON config file <https://docs.habana.ai/en/latest/PyTorch/Inference_on_PyTorch/Quantization/Inference_Using_FP8.html#supported-json-config-file-options>`_. | ||
The measurement configuration file is used during the calibration procedure to collect measurements for a given model. The quantization configuration is used during inference. | ||
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Run Online Inference Using FP8 | ||
------------------------------- | ||
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Once you've completed the model calibration process and collected the measurements, you can run FP8 inference with vLLM using the following command: | ||
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.. code-block:: bash | ||
export QUANT_CONFIG=/path/to/quant/config/inc/meta-llama-3.1-405b-instruct/maxabs_measure_g3.json | ||
vllm serve meta-llama/Llama-3.1-405B-Instruct --quantization inc --kv-cache-dtype fp8_inc --weights-load-device cpu --tensor_paralel_size 8 | ||
.. tip:: | ||
If you are just prototyping or testing your model with FP8, you can use the ``VLLM_SKIP_WARMUP=true`` environment variable to disable the warmup stage, which can take a long time. However, we do not recommend disabling this feature in production environments as it causes a significant performance drop. | ||
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.. tip:: | ||
When using FP8 models, you may experience timeouts caused by the long compilation time of FP8 operations. To mitigate this problem, you can use the below environment variables: | ||
``VLLM_ENGINE_ITERATION_TIMEOUT_S`` - to adjust the vLLM server timeout. You can set the value in seconds, e.g., 600 equals 10 minutes. | ||
``VLLM_RPC_TIMEOUT`` - to adjust the RPC protocol timeout used by the OpenAI-compatible API. This value is in microseconds, e.g., 600000 equals 10 minutes. | ||
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Run Offline Inference Using FP8 | ||
------------------------------- | ||
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To run offline inference (after completing the model calibration process): | ||
* Set the "QUANT_CONFIG" environment variable to point to a JSON configuration file with QUANTIZE mode. | ||
* Pass ``quantization=inc`` and ``kv_cache_dtype=fp8_inc`` as parameters to the ``LLM`` object. | ||
* Call shutdown method of the model_executor at the end of the run. | ||
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.. code-block:: python | ||
from vllm import LLM | ||
llm = LLM("llama3.1/Meta-Llama-3.1-8B-Instruct", quantization="inc", kv_cache_dtype="fp8_inc") | ||
... | ||
# Call llm.generate on the required prompts and sampling params. | ||
... | ||
llm.llm_engine.model_executor.shutdown() | ||
Specifying Device for the Model's Weights Uploading | ||
--------------------------------------------------- | ||
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It is possible to load the unquantized weights on a different device before quantizing them, then moving them to the device on which the model will run. | ||
This reduces the device memory footprint of model weights, as only quantized weights are stored in device memory. | ||
To set the device to upload weights, use the ``weights_load_device`` parameter for the ``LLM`` object, or ``--weights-load-device`` command line parameter when running online inference: | ||
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.. code-block:: python | ||
from vllm import LLM | ||
llm = LLM("llama3.1/Meta-Llama-3.1-8B-Instruct", quantization="inc", kv_cache_dtype="fp8_inc", weights_load_device="cpu") |
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