[Bug]: Mamba should return states in fp32

[toslunar]

Your current environment

N/A

🐛 Describe the bug

There's a difference in the precision of SSM states.

• Authors' implementation uses weight_type, which is usually fp32: https://github.com/state-spaces/mamba/blob/v2.2.4/csrc/selective_scan/selective_scan.cpp#L313
• vLLM implementation uses input_t, which can be 16bit: https://github.com/vllm-project/vllm/blob/v0.7.2/csrc/mamba/mamba_ssm/selective_scan_fwd.cu#L131

This difference seems lowering the quality of generated texts.

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[mzusman]

@toslunar In tests we've done with bf16 , we haven't found evidence for quality degradation, can you share some results or benchmarks?

[github-actions]

This issue has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this issue should remain open. Thank you!

[github-actions]

This issue has been automatically closed due to inactivity. Please feel free to reopen if you feel it is still relevant. Thank you!