[mpich-discuss] Does Asynchronous Allgather work in background without any effects on computing cores?

[Sunwoo Lee]

Hi,

I would like to implement a software that communication and computation are
performed simultaneously. That is, while communication for the current data
is done, the next data is computed overlapping with the communication.

I expected asynchronous MPI such as Iallgather() would make the
communication and computation overlapped. But it seems like the
communication is not started until I call MPI_Wait().

With a simple toy application, I compared the two cases. MPI_IAllgather +
MPI_Wait() versus MPI_Allgather. The issue is that MPI_Wait() takes almost
same time with MPI_Allgather. I can guess the communication is just started
when I call MPI_Wait.

My question is, could asynchronous MPI functions work background so that
computing cores do other works while the communication is performed?

Thank you.

Best,
Sunwoo Lee
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