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.
: 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.
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).
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.
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