[petsc-users] Update of the buffer

[Stefano Zampini]

> On Feb 10, 2022, at 6:00 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Thu, Feb 10, 2022 at 9:17 AM Medane TCHAKOROM <medane.tchakorom at univ-fcomte.fr <mailto:medane.tchakorom at univ-fcomte.fr>> wrote:
> Hello ,
> 
> Sorry if this question does not belong to this mailling list, i'am using Petsc , but with some
> 
> MPI parts code, when dealing with communication.
> 
> If a make two consecutive MPI_Isend requests, and if the destination processor has not yet receive the message inbetween the two calls, will the buffer be updated ? I mean if I send message "1" for the first request, then send "0" as the second message. Will the receiver receive "0" as message ? I not, how can I do to update the message ?
> 
> I believe that MPI guarantees in-order message delivery from a source to a target, so if you send 1 before 0, the receiver
> should get them in that order. However, someone here should know for sure.

I don’t think so. You should use tags to flag the proper operation and wait for it if you need the value to arrive.


> 
>   Thanks,
> 
>     Matt
>  
> Thanks
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>

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