Encoder Decoder Multimodal¶

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
This example shows how to use vLLM for running offline inference with
the explicit/implicit prompt format on enc-dec LMMs for text generation.
"""

import os
import time
from collections.abc import Sequence
from dataclasses import asdict
from typing import NamedTuple

from vllm import LLM, EngineArgs, PromptType, SamplingParams
from vllm.assets.audio import AudioAsset
from vllm.utils import FlexibleArgumentParser


class ModelRequestData(NamedTuple):
    engine_args: EngineArgs
    prompts: Sequence[PromptType]


def run_whisper():
    os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"

    engine_args = EngineArgs(
        model="openai/whisper-large-v3-turbo",
        max_model_len=448,
        max_num_seqs=16,
        limit_mm_per_prompt={"audio": 1},
        dtype="half",
    )

    prompts = [
        {  # Test implicit prompt
            "prompt": "<|startoftranscript|>",
            "multi_modal_data": {
                "audio": AudioAsset("mary_had_lamb").audio_and_sample_rate,
            },
        },
        {  # Test explicit encoder/decoder prompt
            "encoder_prompt": {
                "prompt": "",
                "multi_modal_data": {
                    "audio": AudioAsset("winning_call").audio_and_sample_rate,
                },
            },
            "decoder_prompt": "<|startoftranscript|>",
        },
    ]

    return ModelRequestData(
        engine_args=engine_args,
        prompts=prompts,
    )


model_example_map = {
    "whisper": run_whisper,
}


def parse_args():
    parser = FlexibleArgumentParser(
        description="Demo on using vLLM for offline inference with "
        "vision language models for text generation"
    )
    parser.add_argument(
        "--model-type",
        "-m",
        type=str,
        default="whisper",
        choices=model_example_map.keys(),
        help='Huggingface "model_type".',
    )
    parser.add_argument(
        "--seed",
        type=int,
        default=None,
        help="Set the seed when initializing `vllm.LLM`.",
    )
    return parser.parse_args()


def main(args):
    model = args.model_type
    if model not in model_example_map:
        raise ValueError(f"Model type {model} is not supported.")

    req_data = model_example_map[model]()

    # Disable other modalities to save memory
    default_limits = {"image": 0, "video": 0, "audio": 0}
    req_data.engine_args.limit_mm_per_prompt = default_limits | dict(
        req_data.engine_args.limit_mm_per_prompt or {}
    )

    engine_args = asdict(req_data.engine_args) | {"seed": args.seed}
    llm = LLM(**engine_args)

    prompts = req_data.prompts

    # Create a sampling params object.
    sampling_params = SamplingParams(
        temperature=0,
        top_p=1.0,
        max_tokens=64,
        skip_special_tokens=False,
    )

    start = time.time()

    # Generate output tokens from the prompts. The output is a list of
    # RequestOutput objects that contain the prompt, generated
    # text, and other information.
    outputs = llm.generate(prompts, sampling_params)

    # Print the outputs.
    for output in outputs:
        prompt = output.prompt
        generated_text = output.outputs[0].text
        print(f"Decoder prompt: {prompt!r}, Generated text: {generated_text!r}")

    duration = time.time() - start

    print("Duration:", duration)
    print("RPS:", len(prompts) / duration)


if __name__ == "__main__":
    args = parse_args()
    main(args)