https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Windows-MKL-10-2-vs-10-1-defaulting-to-single-core-single/m-p/910993#M12156 I am running various regression cases on MKL 10.1 vs 10.2 update 2 and 10.2 seems to resolutely insist on only using one core on my machine -( Intel Pentium D 3.Ghz running Windows XP64 ( 64 bit MKL). Of course, OMP_NUM_THREADS=2<BR />I am linking against the OpenMP compatibility libraries<BR /><BR />To run 10.1 vs 10.2 I just drop the new DLLs into my app folder, and re-run the regression cases so repeating various tests s quite easy. It is very,very obvious that 10.2 only uses one core to detriment of solution times.<BR /><BR />Any ideas why this would happen?<BR /><BR />More...<BR />If I reboot my machine, then run a test case then the first run will use both cores. Subsequent runs will only use one core - until I reboot , that is..... Wed, 14 Oct 2009 19:01:46 GMT AndrewC 2009-10-14T19:01:46Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Windows-MKL-10-2-vs-10-1-defaulting-to-single-core-single/m-p/910993#M12156 I am running various regression cases on MKL 10.1 vs 10.2 update 2 and 10.2 seems to resolutely insist on only using one core on my machine -( Intel Pentium D 3.Ghz running Windows XP64 ( 64 bit MKL). Of course, OMP_NUM_THREADS=2<BR />I am linking against the OpenMP compatibility libraries<BR /><BR />To run 10.1 vs 10.2 I just drop the new DLLs into my app folder, and re-run the regression cases so repeating various tests s quite easy. It is very,very obvious that 10.2 only uses one core to detriment of solution times.<BR /><BR />Any ideas why this would happen?<BR /><BR />More...<BR />If I reboot my machine, then run a test case then the first run will use both cores. Subsequent runs will only use one core - until I reboot , that is..... Wed, 14 Oct 2009 19:01:46 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Windows-MKL-10-2-vs-10-1-defaulting-to-single-core-single/m-p/910993#M12156 AndrewC 2009-10-14T19:01:46Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Windows-MKL-10-2-vs-10-1-defaulting-to-single-core-single/m-p/910994#M12157 <DIV style="margin:0px;"> <DIV id="quote_reply" style="width: 100%; margin-top: 5px;"> <DIV style="margin-left:2px;margin-right:2px;">Quoting - <A href="https://community.intel.com/en-us/profile/371334">vasci_intel</A></DIV> <DIV style="background-color:#E5E5E5; padding:5px;border: 1px; border-style: inset;margin-left:2px;margin-right:2px;"><EM>I am running various regression cases on MKL 10.1 vs 10.2 update 2 and 10.2 seems to resolutely insist on only using one core on my machine -( Intel Pentium D 3.Ghz running Windows XP64 ( 64 bit MKL). Of course, OMP_NUM_THREADS=2<BR />I am linking against the OpenMP compatibility libraries<BR /><BR />To run 10.1 vs 10.2 I just drop the new DLLs into my app folder, and re-run the regression cases so repeating various tests s quite easy. It is very,very obvious that 10.2 only uses one core to detriment of solution times.<BR /><BR />Any ideas why this would happen?<BR /><BR />More...<BR />If I reboot my machine, then run a test case then the first run will use both cores. Subsequent runs will only use one core - until I reboot , that is.....</EM></DIV> </DIV> </DIV> <BR />I have answered my own question. I was not setting MKL_DYNAMIC so MKL, in its infinite wisdom, was setting the number of threads to 1. Setting MKL_DYNAMIC=FALSE forces MKL to use the number of threads set by , say, OMP_NUM_THREADS<BR /> Wed, 14 Oct 2009 21:27:46 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Windows-MKL-10-2-vs-10-1-defaulting-to-single-core-single/m-p/910994#M12157 AndrewC 2009-10-14T21:27:46Z