On May 19, 2011, at 9:46 PM, Larry Baker wrote:
> I inquired the same of PGI. Dave Borer, PGI Customer Service Manager, responded:
>> I believe -fast and -fastsse are identical for 64-bit compilers, but there are some differences
>> with 32-bit compilers. I don't think TCP/IP based MPI routines have better performance from
>> optimizations, unless the processes are all running on the same machine. I will ask engineering
>> how messages are passed when all the processes are running on the same hardware.
Ya -- he's pretty much right. When the procs are on the same machine, we end up memcpy'ing through shared memory. Hence, if the memcpy is sped up by using -fast or -fastsse, that would be your extra bonus points. :-)
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