[mpich-discuss] Persistent Communication using MPI_SEND_INIT, MPI_RECV_INIT etc.

[Timothy Stitt]

Hi all,

I've been asking this question around various MPI boards to try and get a consensus before I decide to rewrite some MPI code. I am grateful for any advice that you can give.

I've inherited a MPI code that was written ~8-10 years ago and it predominately uses MPI persistent communication routines for data transfers e.g. MPI_SEND_INIT, MPI_RECV_INIT, MPI_START etc.  (which I am not familiar with and don't normally hear much discussion about). I was just wondering if using persistent communication calls is still regarded as the most efficient/scalable way to perform communication when the communication pattern is known and fixed amongst neighborhood processes? We regularly run the code across an IB network so would there be a benefit to rewrite the code using another approach (e.g. MPI one-sided communication) or should I leave it as it is? The code currently scales up to 10K cores and I want to push it even further and thus was wondering if there is any benefit in tinkering with this persistent MPI communication approach?

Thanks in advance for any advice.

Tim.