Cisco’s Jeff Squyres writes that most modern MPI implementations using connection-based network transports utilize a “lazy connection” management scheme.
One of the nice features of MPI is that its applications don’t have to worry about connection management. There’s no concept of “open a connection to peer X” — in MPI, you just send or receive from peer X. This is somewhat similar to many connectionless network transports (e.g., UDP) where you just send to a target address without explicitly creating a connection to that address. But it’s different in a key way from many connectionless transports (e.g., UDP): MPI’s transport is reliable, meaning that whatever you send is guaranteed to get there.
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