From: Anders Jorgensen Newsgroups: comp.parallel.pvm Subject: Re: pvm vs. mpi Date: Wed, 12 May 1999 14:38:55 -0600 Organization: Los Alamos National Laboratory Message-Id: <3739E6DF.40F60164@lanl.gov> References: <3736D96A.41C6@physik.uni-karlsruhe.de> <37374E2B.9CBD6C79@lanl.gov> <3737D1D2.CF54E42F@ti.uni-mannheim.de> Reply-To: anders.jorgensen.1998@alum.bu.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Xref: ukc comp.parallel.pvm:8372 Uh oh.. I'm starting a thread here.. but I just can't help it. Lars Rzymianowicz wrote: > > Anders Jorgensen wrote: > > 1) PVM can operate across multiple architectures, automatically > > converting data format when sending between different architectures. > > So does MPI. At least you can run your app on a heterogeneous cluster. > There are also functions for data conversion, but i'm not 100% sure, if > they are called automatically... > > > 2) PVM is fault tolerant. If a node goes down, or a job dies, the PVM > > system will detect it, and notify your program. > > Nah, the term "fault tolerant" is a bit misused here. MPI will also > "detect" a process failure by just hanging or stoping...so does PVM. > "Fault Tolerance" would mean that another process is started > automatically and takes over. But neither of them is able to do this. > Again with out intending any flame, I beg to differ. I mentioned it will notify your program. You have to take care of handling that error, but that is a different matter. However that mere action is miles beyond what MPI does. If you are running on a non-dedicated cluster, then PVM is absolutely essential, since you have no control over the different machines in the cluster. I know on my network, reboots etc. happen many times a day, running on about 120 machines. If the machines are dedicated and under your control, and you have a reliable network, then MPI is probably fine. But PVM is really a "grassroots" (or socialist :-) parallel system in the way that resources can be shared on an "as-available" basis. The nice thing is that it will run huge apps with a very limited hardware investment, whereas MPI almost requires a huge hardware investment aswell - because of the need for dedicated hardware.. PVM may be cheap, but that doesn't mean it's a toy. If you are doing process-farming like stuff (which I do), PVM is ideal. If you are doing heavy duty communication in a matrix, and you have reliable hardware, then MPI is probably best. OK.. just to avoid starting a war here, I won't discuss this any further (at least not in relation to this thread :-). ---anders