[Question] I found that ois is numerically equivalent to tis during training

Your Question

Hi,
I am training Qwen3.5-4B with Slime v0.2.4 with the following config:

• async
• update weight step = 2
• use tis
  When I look at the logged metrics, I found that OIS is numerically equal to TIS during training, which should not happen. Is this a bug or something expected? Thanks in advance for any help.

Here are the figures:

What I've Tried

I read through the code and found they should not be equal to each other

Environment (if relevant)

• slime version: v0.2.4
• Python version:
• PyTorch version:
• CUDA/ROCm version:
• GPU type and count:
• OS:

Additional Context

No response

Pre-submission Checklist

• I have read the CONTRIBUTING.md and understand the collaboration scope.
• I have read the documentation and FAQ and my question is not answered there.
• I have searched for existing issues and my question has not been asked before.

Start by reproducing the reported training setup in Slime v0.2.4: async mode, update weight step 2, and TIS enabled. Compare the logged OIS and TIS metrics against the expected distinction; done means determining whether their equality is expected or producing a reproducible bug report with the missing environment details.