Hello Masoud, Responded inline
Thanks, William From: devel <devel-boun...@lists.open-mpi.org> on behalf of Masoud Hemmatpour via devel <devel@lists.open-mpi.org> Reply-To: Open MPI Developers <devel@lists.open-mpi.org> Date: Wednesday, April 20, 2022 at 5:29 AM To: Open MPI Developers <devel@lists.open-mpi.org> Cc: Masoud Hemmatpour <mashe...@gmail.com> Subject: [EXTERNAL] [OMPI devel] RDMA and OMPI implementation CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. Hello Everyone, Sorry, MPI is quite new for me, in particular the implementation. If you don't mind, I have some very basic questions regarding the OMPI implementation. If I use one-sided MPI operations (Get, and Put) forcefully I use RDMA? – It depends, but it’s not guaranteed. For example, in Open MPI 4.0.x, there was the osc/pt2pt component that implemented osc operations using send/receive. Or for example, with calls to libfabric’s osc api, it depends on the implementation of the underlying provider. Is it possible to have one-sided without RDMA? - Yes In general, other types of MPI operations like Send/Receive or collective operations are implemented using RDMA or not necessarily? – Not necessarily. For example, using TCP won’t use RDMA. The underlying communication protocol could very well implement send/receive using RDMA though. How can I be sure that I am using RDMA for a specific operation? – I’m not sure there’s an easy way to do this, I think you have to have some understanding of what communication protocol you’re using and what that protocol is doing. Thank you very much in advance for your help! Best Regards,
