[mpich-discuss] How to use non-blocking send/receive without calling MPI_Wait

[Atchley, Scott]

On Apr 7, 2015, at 7:45 PM, Jeff Hammond <jeff.science at gmail.com> wrote:

>>>> I don't expect MPI to make async progress on Ethernet unless you have a comm thread in MPI poking the network.
>>> 
>>> Friendly reminder, Jeff: Ethernet != sockets.  The statement you are making is generally true for sockets but not necessarily for Ethernet.
>>> 
>> 
>> I bit my tongue for the same reasons… ;-)
> 
> Correction: I do not expect MPICH to make async progress on Ethernet
> (because it uses sockets).

Does MPICH make async progress on InfiniBand using Verbs without calling into MPI_Test*/MPI_Wait*? Does MPICH not fragment large RDMAs? Yes, the HCA (why can’t they call it a NIC?) will offload much of the work, but not all of it. Matching is still done in the host and only when invoked by the app calling into Test/Wait or a progress thread doing it on the app’s behalf.

> I'm not sure how this in any way affects the conversation being had,
> other than to demonstrate that chemists are unreliable sources of
> information about networking hardware ;-)

It is not just chemists. I hear HPC computer scientists say the same thing… ;-)

Scott
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