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CUDA-x86.

mul24 for CUDA Fortran?

 
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TheMatt



Joined: 06 Jul 2009
Posts: 306
Location: Greenbelt, MD

PostPosted: Thu Jul 01, 2010 7:57 am    Post subject: mul24 for CUDA Fortran? Reply with quote

As I try everything for that last bit of performance, I was wondering, is there a way to use mul24 with CUDA Fortran? The -Mcuda help print doesn't seem to have it as a viable option (whereas it does exist for -ta=nvidia).

I have no idea if it'll help, but I have to try!
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mkcolg



Joined: 30 Jun 2004
Posts: 5952
Location: The Portland Group Inc.

PostPosted: Thu Jul 01, 2010 2:15 pm    Post subject: Reply with quote

Hi Matt,

Sorry, no mul24 sub-option for -Mcuda. In CUDA C, the programmer needs to explicitly call "__mul24(x,y)" to get the t 24-bit multiply. We might be able to add this as a callable routine, but it's my understanding that 24-bit multiplies are slower than the default on a Fermi so it would have a short shelf life in terms of usefulness.

Important?

- Mat
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TheMatt



Joined: 06 Jul 2009
Posts: 306
Location: Greenbelt, MD

PostPosted: Fri Jul 02, 2010 7:51 am    Post subject: Reply with quote

Mat,

No, it's probably not that important--there aren't many integer multiplies--but I thought I'd ask.

Thanks,
Matt
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