vllm/tests/distributed/test_torchrun_example.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

# unit test for `examples/features/torchrun/torchrun_example_offline.py`
import os
import random

import torch.distributed as dist

from vllm import LLM, SamplingParams
from vllm.distributed.parallel_state import get_world_group

# Let PyTorch choose the WORLD backend for the current device type.
dist.init_process_group()

# Create prompts
prompts = [
    "Hello, my name is",
    "The president of the United States is",
    "The capital of France is",
    "The future of AI is",
]

sampling_params = SamplingParams(temperature=0.8, top_p=0.95)

# set different `gpu_memory_utilization` for different ranks,
# to test if all ranks agree on the same kv cache configuration.
llm = LLM(
    model="facebook/opt-125m",
    tensor_parallel_size=2,
    pipeline_parallel_size=int(os.getenv("PP_SIZE", 1)),
    distributed_executor_backend="external_launcher",
    gpu_memory_utilization=random.uniform(0.8, 0.92),
    seed=0,
)

outputs = llm.generate(prompts, sampling_params)

cpu_group = get_world_group().cpu_group

torch_rank = dist.get_rank(group=cpu_group)


def test_consistent_across_ranks(obj):
    if torch_rank == 0:
        dist.broadcast_object_list([obj], src=0, group=cpu_group)
    else:
        container = [None]
        dist.broadcast_object_list(container, src=0, group=cpu_group)
        assert container[0] == obj


test_consistent_across_ranks(llm.llm_engine.vllm_config.cache_config.num_cpu_blocks)
test_consistent_across_ranks(llm.llm_engine.vllm_config.cache_config.num_gpu_blocks)

# make sure we can access the model parameters from the calling process
# of the `LLM` instance.
params = list(
    llm.llm_engine.model_executor.driver_worker.worker.model_runner.model.parameters()
)
test_consistent_across_ranks(len(params))

# all ranks should have the same outputs
for output in outputs:
    prompt = output.prompt
    generated_text = output.outputs[0].text
    test_consistent_across_ranks(prompt)
    test_consistent_across_ranks(generated_text)
    print(f"Rank {torch_rank}, Prompt: {prompt!r}, Generated text: {generated_text!r}")