topic Re: Does enabling hyperthreading or not have any effect on MKL in Intel® oneAPI Math Kernel Library

Does enabling hyperthreading or not have any effect on MKL performance?

Tony_Garratt — Wed, 01 Jul 2009 20:10:47 GMT

Does enabling hyperthreading or not have any effect on the performance (speed) of MKL, in particular BLAS and LAPACK routines?

Re: Does enabling hyperthreading or not have any effect on MKL

Shane_S_Intel — Wed, 01 Jul 2009 20:33:24 GMT

Quoting - Tony Garratt

Does enabling hyperthreading or not have any effect on the performance (speed) of MKL, in particular BLAS and LAPACK routines?

Hi Tony, we typically recommend against enabling HT because it has a negative effect on BLAS/LAPACK performance. See the knowledge base article: http://software.intel.com/en-us/articles/setting-thread-affinity-on-smt-or-ht-enabled-systems/.
-Shane

Re: Does enabling hyperthreading or not have any effect on MKL

TimP — Wed, 01 Jul 2009 20:48:59 GMT

Quoting - Shane Story (Intel)

set KMP_AFFINITY= physical[,0,verbose]
and
OMP_NUM_THREADS <= number of available cores
if you require run with HT enabled and have a recent libiomp which supports this KMP option. As Shane suggests, an application such as MKL which can keep the FPU and other resources busy will not benefit from sharing the important resources among threads.
Shane, Thanks for the KB. It should be required reading for management and marketing.

Re: Does enabling hyperthreading or not have any effect on MKL

Tony_Garratt — Wed, 01 Jul 2009 21:36:57 GMT

Thank you!