From: "Alain Coetmeur" Newsgroups: comp.parallel.mpi Subject: Re: Context in mpi Date: Thu, 24 Dec 1998 17:03:54 +0100 Organization: Informatique-CDC Message-Id: <75tq80$pt86@puligny.idt.cdc.fr> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Brandon Mitchell a écrit dans le message ... >I'm building a layer above mpi as part of a research project. It involves >me keeping a buffer for up to one message from each host. I then pass the >message from the buffer to the users process that calls my version of >MPI_Recv. > I'd like to see what sources are in the comm that is passed to >my verion of MPI_Recv. I don't understand your intentions. if you want to know from where come a message, then the MPI_Status filled by MPI_Recv contain informations like the rank of the sender relative to the MPI_Communicator you use. if you want to know from whom is a message that is coming, without getting it really, try to use MPI_Iprobe that set the status like MPI_recv but does not read the data, yet it guatantee that calling a MPI_Recv with the same parameters return this message. for other intention, like queue messages separately from each host, use asynchronous receive like MPI_Irecv , and MPI_Test or MPI_Wait (any,some) to check when data are really received. for your proble you can try to launch one async receive in a buffer for each potential sender and MPI_Test if data is received. > Is that possible? Looking at the source of MPICH, >it looks like I'll need to add some functionallity that I don't want to >add. this would break compatibility with other MPI implementation, breaking portability...