[Model] Fix minimax model cache & lm_head precision

[qscqesze]

Change the precision of the MiniMax model in vLLM: update the LM head and KV cache from bfloat16 (bf16) to float32 (fp32).
Purpose: To improve numerical stability and output accuracy during inference.

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[houseroad]

Could you provide some precision comparison results?

[qscqesze]

Could you provide some precision comparison results?

We conducted the AIME24 evaluation using the minimax-text-01 model and observed that the scores were relatively low. Upon further investigation, we noticed two types of issues: in some cases, the model failed to output certain expected characters, while in other cases, it produced repeated outputs.

After thorough debugging, we identified that the root cause was insufficient precision in both the KV cache and LM head outputs. Adjusting these components to higher precision resolved the problem and improved output stability and accuracy.

[DarkLight1337]

Thanks, this LGTM

[houseroad]

Yeah, I mean list some scores (before vs after the changes) in the PR description to help folks understand the impact of the changes. :-)