[mpich-discuss] MPI_Send over ibverbs

[Joachim Jenke]

Hi,

none of the MPI send calls has a requirement to return after the message 
was received. MPI_Send can return as soon as the caller can write to 
buffer without impact to the data being transferred. This might be after 
the data is put to the network, or the MPI library copied the data to an 
internal buffer.

MPI_Ssend has the requirement to return after the message was matched at 
the receiver, which implies that the matching Receive was called. But it 
still does not require that the message was received at this point.

Best
Joachim

Am 08.10.24 um 04:55 schrieb Niyaz Murshed via discuss:
> Hi,
> 
> Is there a way to check the implementation of MPI_Send?
> 
> As I understand there is an implicit barrier which allows MPI_Send to 
> return only after the buffer is received by the destination.
> 
> How is this communication done? How does the destination notify the 
> sender that buffer is received?
> 
> How is this implemented when using rocev2 ?
> 
> Regards,
> 
> Niyaz
> 
> 
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-- 
Dr. rer. nat. Joachim Jenke

IT Center
Group: High Performance Computing
Division: Computational Science and Engineering
RWTH Aachen University
Seffenter Weg 23
D 52074  Aachen (Germany)
Tel: +49 241 80- 24765
Fax: +49 241 80-624765
jenke at itc.rwth-aachen.de
www.itc.rwth-aachen.de
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