What is the system default buffer size for MPI_Send? Are there any environment variables to set?

[duqi-hnu]

What is the system default buffer size for MPI_Send? Are there any environment variables to set?

[hzhou]

Cound you provide some context about your question? Depending on the actual message paths and lower layer devices, different types and amounts of buffers may be used or may not use buffers at all.

[duqi-hnu]

MPICH-4.2.2

[hzhou]

Could you try changing the tag into src_rank + 100 * dst_rank?

[duqi-hnu]

After the tag is modified, runs properly

[hzhou]

The issue is due to exceeding maximum tag value. You can query the upper bound of tag value using MPI_Comm_get_attr with key MPI_TAG_UB.

[duqi-hnu]

thanks