From: Duge de Bernonville Rodolphe Newsgroups: comp.parallel.mpi Subject: Re: membership test for group/communicator Date: Mon, 26 Apr 1999 15:49:13 +0200 Organization: Universite Bordeaux I Message-Id: <37246ED9.2A06@info.enserb.u-bordeaux.fr> References: <7fqvoq$o9c@henrici.Stanford.EDU> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit MNNTP-Posting-Host: spendius.enserb.u-bordeaux.fr Xref: ukc comp.parallel.mpi:4987 Erik Boman wrote: > > Does anybody know how to test for membership in a group or communicator? > My situation is a communicator is passed into my subroutine. > Possibly there are processes that are not in this communicator, > so I need to find out which processes belong to it and which don't. > > I couldn't find any suitable query function in the MPI 1.1 standard, > so I thought maybe I could use MPI_Comm_rank to figure it out. > Unfortunately MPICH aborts if I call MPI_Comm_rank with processes that are > not in the communicator :-( > > Any suggestions? I'm sure others must have encountered this problem. > > Thanks, > Erik Boman > boman@cs.stanford.edu - To test membership in a group : MPI_Group_rank returns MPI_UNDEFINED if the process is not a member (integer). - To test membership in a communicator : its quite strange but its true that MPI_Comm_rank always return MPI_SUCCESS. So maybe you can try this : MPI_Comm_group to have the group of the communicator and so MPI_Group_rank. Well, I hope it will work ?