From: Lars Rzymianowicz Newsgroups: comp.parallel.mpi Subject: Re: MPI Barriers and pending communications Date: Fri, 28 May 1999 08:34:41 +0200 Organization: Dept. of Computer Engineering, University of Mannheim, Germany Message-Id: <374E3901.855BB860@ti.uni-mannheim.de> References: <7ikep9$rh9$1@lll-winken.llnl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Xref: ukc comp.parallel.mpi:5141 Greg P Tomaschke wrote: > Does a call to MPI_Barrier guarantee that all previously-sent messages > will have "arrived" when the barrier is exited? No, it only guarantees that all processes continue their work after all have entered the barrier. Nothing is said about pending send/rcvs. If you have a regular communication pattern with a fixed number of messages, you don't need this at all. If you don't have it, blocking send/rcvs (could degrade perf) could help. Or use special TAGS or messages to notify all other processes that you have sent all your messages. If you got this sort of messages from everyone, it's done. Any better ideas? Lars -- Homepage: http://mufasa.informatik.uni-mannheim.de/lsra/persons/lars/