vllm/examples/offline_inference/basic

Basic

The LLM class provides the primary Python interface for doing offline inference, which is interacting with a model without using a separate model inference server.

Usage

The first script in this example shows the most basic usage of vLLM. If you are new to Python and vLLM, you should start here.

python examples/offline_inference/basic/basic.py

The rest of the scripts include an argument parser, which you can use to pass any arguments that are compatible with LLM. Try running the script with --help for a list of all available arguments.

python examples/offline_inference/basic/classify.py

python examples/offline_inference/basic/embed.py

python examples/offline_inference/basic/score.py

The chat and generate scripts also accept the sampling parameters: max_tokens, temperature, top_p and top_k.

python examples/offline_inference/basic/chat.py

python examples/offline_inference/basic/generate.py

Features

In the scripts that support passing arguments, you can experiment with the following features.

Default generation config

The --generation-config argument specifies where the generation config will be loaded from when calling LLM.get_default_sampling_params(). If set to ‘auto’, the generation config will be loaded from model path. If set to a folder path, the generation config will be loaded from the specified folder path. If it is not provided, vLLM defaults will be used.

If max_new_tokens is specified in generation config, then it sets a server-wide limit on the number of output tokens for all requests.

Try it yourself with the following argument:

--generation-config auto

Quantization

GGUF

vLLM supports models that are quantized using GGUF.

Try one yourself by downloading a quantized GGUF model and using the following arguments:

from huggingface_hub import hf_hub_download
repo_id = "bartowski/Phi-3-medium-4k-instruct-GGUF"
filename = "Phi-3-medium-4k-instruct-IQ2_M.gguf"
print(hf_hub_download(repo_id, filename=filename))

--model {local-path-printed-above} --tokenizer microsoft/Phi-3-medium-4k-instruct

CPU offload

The --cpu-offload-gb argument can be seen as a virtual way to increase the GPU memory size. For example, if you have one 24 GB GPU and set this to 10, virtually you can think of it as a 34 GB GPU. Then you can load a 13B model with BF16 weight, which requires at least 26GB GPU memory. Note that this requires fast CPU-GPU interconnect, as part of the model is loaded from CPU memory to GPU memory on the fly in each model forward pass.

Try it yourself with the following arguments:

--model meta-llama/Llama-2-13b-chat-hf --cpu-offload-gb 10