[Bugfix] OpenAI entrypoint limits logprobs while ignoring server defined --max-logprobs

[maor-ps]

Current check implementation disregards the server parameters --max-logprobs and restricts the logprobs returned from the server. This modification removes the upper limit and ensures that the logprobs values are only checked to be positive integers.

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[simon-mo]

cc @robertgshaw2-neuralmagic

I believe this is partly intentional to (1) cap the memory usage (2) follow OpenAI's convention. But we should still allow the cap to be configurable.

[maor-ps]

cc @robertgshaw2-neuralmagic

I believe this is partly intentional to (1) cap the memory usage (2) follow OpenAI's convention. But we should still allow the cap to be configurable.

@simon-mo
The capping is already handled on the vllm side when running the server, with the default max-logprobs set to 5. If the OpenAI entrypoint requests a larger number, vllm will throw an error.

[DarkLight1337]

OpenAI's Chat Completion API supports up to top_logprobs=20 (as opposed to logprobs=5 for legacy Completion API). Should we increase the default ModelConflig.max_logprobs accordingly?

[DarkLight1337]

Since max_logprobs only imposes a limit on the user, it should be fine to increase the default value. I have pushed a commit that increases max_logprobs to the value required by Chat Completions API.