[mpich-discuss] Better alternatives of MPI_Allreduce()

Benson Muite benson_muite at emailplus.org
Tue May 5 01:57:43 CDT 2020

On Tue, May 5, 2020, at 8:38 AM, hritikesh semwal via discuss wrote:
> Hello all,
> I am working on the development of a parallel CFD solver and I am using MPI_Allreduce for the global summation of the local errors calculated on all processes of a group and the summation is to be used by all the processes. My concern is that MPI_Allreduce is taking almost 27-30% of the total time used, which is a significant amount. So, I want to ask if anyone can suggest me better alternative/s to replace MPI_Allreduce which can reduce the time consumption.
> Thank you.
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Hi Hitesh,

What hardware are you running on and what is the interconnect?
Have you tried changing any of the MPI settings?
Can the reduction be done asynchronously?

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