> On Feb 10, 2022, at 6:00 PM, Matthew Knepley <[email protected]> wrote: > > On Thu, Feb 10, 2022 at 9:17 AM Medane TCHAKOROM > <[email protected] <mailto:[email protected]>> > 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/>
