[Bug]: external_dp blocks normal DP group creation

[Selkh]

Your current environment

0.8.0 & 0.8.1

🐛 Describe the bug

#14899 introduces error for normal DP.

As https://github.com/vllm-project/vllm/blob/main/vllm/distributed/parallel_state.py#L904C35-L904C45 shown, "config.parallel_config.world_size" means tp-size * pp-size defined in config.py while world_size is size of all visible devices from "torch.distributed". As a result, as long as a regular DP size, it will enter this branch as unexpected, thereby preventing the establishment of DP group.

Suppose replace "config.parallel_config.world_size" with "config.parallel_config.world_size_cross_dp" which matches the design of external_dp more.

if config.parallel_config.world_size_cross_dp != world_size:

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[youkaichao]

looks true, wonder why we don't see it in the test :(

[youkaichao]

can you create a pr to fix it?

[Selkh]

can you create a pr to fix it?

Sure. Thanks for your prompt feedback again.

[youkaichao]

@Selkh hi, i'm fixing it in #15355 , please check if it works.

[Selkh]

@Selkh hi, i'm fixing it in #15355 , please check if it works.

Okay, it looks more compatible and extensible. I will verify locally whether it works as expected.