[mpich-discuss] Semantics of MPI_Cancel

[Matthieu Dorier]

So either there is no way to know which MPI_Send will be matched, since even with
MPI_Irecv(req); MPI_Test(flag,req); if(!flag) {MPI_Cancel(req)} MPI_Recv()
the MPI_Irecv could have completed between the MPI_Test and the MPI_Cancel...

Or does the content of the MPI_Irecv, which is supposed to have been put in the user-provided buffer, gets transferred into the buffer of the next MPI_Recv upon cancellation of the MPI_Irecv?

Thanks,

Matthieu

----- Mail original -----
> De: "Rajeev Thakur" <thakur at mcs.anl.gov>
> À: discuss at mpich.org
> Envoyé: Mercredi 7 Août 2013 16:10:02
> Objet: Re: [mpich-discuss] Semantics of MPI_Cancel
> 
> You canceled the recv, not the send. The send will still go through
> and match the first available receive that can be matched.
> 
> On Aug 7, 2013, at 3:25 PM, Matthieu Dorier wrote:
> 
> > Hi,
> > 
> > Suppose process 0 does the following
> > MPI_Irecv(...req)
> > MPI_Cancel(req)
> > MPI_Recv
> > 
> > and process 1 does
> > MPI_Send
> > MPI_Send
> > 
> > Does process 0 receives the data from the first or the second
> > MPI_Send?
> > (I'd tend to say the second, but I'd like a confirmation).
> > 
> > Thanks!
> > 
> > Matthieu Dorier
> > PhD student at ENS Cachan Brittany and IRISA
> > http://people.irisa.fr/Matthieu.Dorier
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