IMKL 10.0 FFT

[IRCAnonymous__IRCAn1]

I am about to install a new Linux system and experiment with the IMKL to improve the speed of some FFTs we perform. Can anyone give me a rough speed comparision between 64 bit and 32 bit binaries when using IMKL 10 for FFTs? I want to know whether the 64 bit ISA outweighs the cache penalty for 64 bits, and whether I should go with a 32 bit or 64 bit OS. Thanks!

[TimP]

I don't know what you mean by "64 bit ISA outweighs the cache penalty for 64 bits." The usual reason for going with a 32-bit OS on a 64-bit capable machine would be that you don't want to buy 2 more memory sticks. I can't see that the code size in a 64-bit MKL FFT would be enough bigger than the 32-bit code size to incur measurable instruction cache misses, but you can easily compare performance of the 32-and 64-bit MKL if you choose a 64-bit OS. I don't know if anyone tested the MKL this way, but there is seldom more than 1% penalty for running a 32-bit application under a 64-bit OS rather than a 32-bit one. If such small differences are important, install both linux versions dual boot and compare them.

[IRCAnonymous__IRCAn1]

Sorry, I should have been more specific. Driver code that I have is currently limited to a 32 bit OS. I want to know if the performance advantage of going to 64 bit for the FFTs is worth the pain of working with the people who wrote the driver to make it work with 64 bit.

Thanks