Intel® oneAPI Math Kernel Library
Ask questions and share information with other developers who use Intel® Math Kernel Library.
Announcements
FPGA community forums and blogs on community.intel.com are migrating to the new Altera Community and are read-only. For urgent support needs during this transition, please visit the FPGA Design Resources page or contact an Altera Authorized Distributor.
7234 Discussions

Speed of DGGHRD and DGGHD3

thijssteel
Beginner
‎08-05-2020 02:11 AM
1,100 Views

I noticed something about the routines DGGHRD and DGGHD3. They both reduce a pencil to Hessenberg triangular form for use in the QZ algorithm, with DGGHD3 being the blocked version.

When linked with the reference LAPACK or with OpenBLAS, DGGHD3 is faster than DHHGRD. However, when the test program is linked with MKL, DGGHD3 loses its speed advantage. I also don't see any multicore usage in that routine when linked with MKL. Is it possible that the blocked version is not (fully) implemented in MKL?

Labels (1)
Labels:
0 Kudos

Link Copied

1 Reply
thijssteel
Beginner
‎08-05-2020 10:32 AM
1,090 Views

Update, it looks like the blocksize returned by ilaenv is always 1 for DGGHD3. Changing that seems to fix the performance issue.

0 Kudos
Copy link
Reply

Community support is provided Monday to Friday. Other contact methods are available here.

Intel does not verify all solutions, including but not limited to any file transfers that may appear in this community. Accordingly, Intel disclaims all express and implied warranties, including without limitation, the implied warranties of merchantability, fitness for a particular purpose, and non-infringement, as well as any warranty arising from course of performance, course of dealing, or usage in trade.

For more complete information about compiler optimizations, see our Optimization Notice.