Source examples/offline_inference/chat.py.

Chat

from vllm import LLM, SamplingParams

llm = LLM(model="meta-llama/Meta-Llama-3-8B-Instruct")
sampling_params = SamplingParams(temperature=0.5)


def print_outputs(outputs):
    for output in outputs:
        prompt = output.prompt
        generated_text = output.outputs[0].text
        print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")
    print("-" * 80)


print("=" * 80)

# In this script, we demonstrate how to pass input to the chat method:

conversation = [
    {
        "role": "system",
        "content": "You are a helpful assistant"
    },
    {
        "role": "user",
        "content": "Hello"
    },
    {
        "role": "assistant",
        "content": "Hello! How can I assist you today?"
    },
    {
        "role": "user",
        "content": "Write an essay about the importance of higher education.",
    },
]
outputs = llm.chat(conversation,
                   sampling_params=sampling_params,
                   use_tqdm=False)
print_outputs(outputs)

# You can run batch inference with llm.chat API
conversation = [
    {
        "role": "system",
        "content": "You are a helpful assistant"
    },
    {
        "role": "user",
        "content": "Hello"
    },
    {
        "role": "assistant",
        "content": "Hello! How can I assist you today?"
    },
    {
        "role": "user",
        "content": "Write an essay about the importance of higher education.",
    },
]
conversations = [conversation for _ in range(10)]

# We turn on tqdm progress bar to verify it's indeed running batch inference
outputs = llm.chat(messages=conversations,
                   sampling_params=sampling_params,
                   use_tqdm=True)
print_outputs(outputs)

# A chat template can be optionally supplied.
# If not, the model will use its default chat template.

# with open('template_falcon_180b.jinja', "r") as f:
#     chat_template = f.read()

# outputs = llm.chat(
#     conversations,
#     sampling_params=sampling_params,
#     use_tqdm=False,
#     chat_template=chat_template,
# )