MPI-2 chapter 7 is all about the extended collective operations -- for each collective, it defines which process is supposed to pass in MPI_ROOT, etc.
Specifically, check out MPI-2 section 7.3.2, "Operations that Move Data" (it's a very long section; a sub-section for each MPI collective). > -----Original Message----- > From: users-boun...@open-mpi.org > [mailto:users-boun...@open-mpi.org] On Behalf Of Michael Kluskens > Sent: Monday, March 27, 2006 10:49 AM > To: Open MPI Users > Subject: Re: [OMPI users] MPI_ROOT - required where/when? > > Edgar, > > Thank you. I was using MPI_ROOT in a MPI_Bcast call from > the parent > process where I spawn subprocesses and it worked fine in OpenMPI but > when it didn't work on another platform and the support engineers > solution was to define it as zero I started looking and > couldn't find > anything close to what you said below in the four books I > have. Page > 236 of Using MPI-2 shows the correct use of MPI_ROOT but no > explanation of why. > > Michael > > On Mar 27, 2006, at 10:21 AM, Edgar Gabriel wrote: > > > MPI_ROOT is required for the rooted operations of the inter- > > communicator > > collectives in MPI-2, I am not aware of that you need MPI_ROOT in > > intra-communicator collectives as defined in MPI-1. > > > > Thanks > > Edgar > > > > Michael Kluskens wrote: > >> The constant MPI_ROOT is not universally defined in all current > >> shipping MPI implementations. > >> > >> Is there any MPI function/call that requires MPI_ROOT? > >> > >> From the complete reference it appears that MPI_ALLGATHER might be > >> the one routine. > >> > >> > >> This all relates to portability, code I write using OpenMPI has to > >> work on other systems not using OpenMPI. > >> > >> Michael > >> > >> _______________________________________________ > >> users mailing list > >> us...@open-mpi.org > >> http://www.open-mpi.org/mailman/listinfo.cgi/users > > _______________________________________________ > > users mailing list > > us...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/users > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users >
