Messages in this thread | | | Date | Wed, 17 Jun 1998 12:03:45 -0400 (EDT) | From | <> | Subject | Re: Remote fork() and Parallel programming |
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On Tue, 16 Jun 1998, Larry McVoy wrote:
> : I realized that I might someday want to run my app on a 100 node cluster > : insted of just my SMP system... MPI seemed to be a better (performance > : wise) solution to cluster programming, although it did require non-trivial > : effort to program using it at first. > > Agreed on both points; though I claim that it is good for your brain to fit > your computation into messages, it tends to make some other nice things > happen in the design of your code.
Yes, I can agree with that. I gained a deeper understanding of what data is needed where by using MPI insted of DSM.
> : It seemed wiser to write my software for MPI and deal with the > : difficulties and it being non-optimum on my smp system. (Although I've > : never tested it, I'm sure that shared memory on a smp system is *MUCH* > : faster then MPI)... > > Actually, only if you don't do anything to the MPI libraries. I.e., they > are doing networking through the loopback device.
Yes. Though I seem to recall that the Linux loopback device does jump over a fair portion of the stack.
> SGI took the libs, gutted 'em, leaving just the interfaces, and tuned them > especially for SMP machines (yeah, they can still call out to the networking > ones when they need to).
I posted yesturday to your cluster list about doing this on Linux.. I would very much like to see this.. Perhaps it would be wise to first optimize MPI for SMP systems, then optimize MPI for Linux clusters.
> They even did some VM hacking such that they could map another process' > address space so that a send() turned into > > find the process associated with the destination > make we've already mapped the destination > bcopy() > > It was damn close to no more than the bcopy() cost.
Sounds good here..
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