topic Re: CBLAS matrix order and overhead? in Intel® oneAPI Math Kernel Library

CBLAS matrix order and overhead?

Michael_Stauffer — Wed, 06 May 2009 21:30:03 GMT

Hi,

Do the CBLAS matrix routines reorder the matrix array(s) from row-major to column-major in order to use the underlying Fortran BLAS implementation? Or should I pass column-ordered matricies when calling with CBLAS? If the former, there must be some overhead involved in the conversion. Thanks.

BTW, I haven't found a way to search a particular forum. The search box on the side of the forum page let's me choose to search forums, but not a particular one, and seems the same for Advanced Search. Am I missing something?

Cheers,

Michael

Re: CBLAS matrix order and overhead?

Andrey_Bespalov — Thu, 21 May 2009 09:35:14 GMT

CBLAS doesn't reoder the matrix arrays.

Re: CBLAS matrix order and overhead?

Michael_Stauffer — Thu, 21 May 2009 15:46:58 GMT

Quoting - Andrey Bespalov (Intel)

CBLAS doesn't reoder the matrix arrays.

Thanks, very good to know. I should have experimented more first. Since the interface requries passing the order of the array, it suggests it doesn't reorder. But still, good to know from the source.

So, the only performance penalty is negligible, the cost of the C wrapper to the Fortan lib?

Cheers

Re: CBLAS matrix order and overhead?

Andrey_Bespalov — Fri, 22 May 2009 05:05:17 GMT

Yes, exactly.

Re: CBLAS matrix order and overhead?

mgstauffer — Fri, 22 May 2009 14:10:11 GMT

Quoting - Andrey Bespalov (Intel)

Yes, exactly.

Great, thanks.