[Wien] Wien2k on AVX512 CPUs

[Pavel Ondračka]

Dear mailing list,

just out of curiosity has anyone any experience running Wien2k on a
AVX512 capable machine (eg. the KNL accelerators or recent Intel
skylake-avx512 CPUs)?

Recently my cluster updated to this skylake-avx512 machines however I'm
unable to get any better performance for Wien2k. In particular MKL seem
to suck, for example in single core performance (with the serial
test_case) the eigenvalue problem is actually faster when I forbid the
usage of AVX512 instructions:

running with MKL_VERBOSE=1 MKL_ENABLE_INSTRUCTIONS=AVX2
MKL_VERBOSE
ZHETRD(L,3481,0x2b74d8567cc0,3481,0x2b74d82121c0,0x2b74d8218e88,0x2b74e
f769b00,0x2b74ef777490,452530,0) 10.21s CNR:OFF Dyn:1 FastMM:1
TID:0  NThr:1

with MKL_ENABLE_INSTRUCTIONS=AVX512
MKL_VERBOSE
ZHETRD(L,3481,0x2b5397c96cc0,3481,0x2b53979411c0,0x2b5397947e88,0x2b53a
ee98b00,0x2b53aeea6490,452530,0) 12.31s CNR:OFF Dyn:1 FastMM:1
TID:0  NThr:1

This is somewhat compensated by speedups in the hamilt part (the VML
stuff and various ?GEMMs seem to be actually slightly faster), but
overall the performance is mostly the same with and without the AVX512
stuff. OpenBLAS is maybe 15% slower so not an option as well...

Moreover for MPI version I'm not able to get a correctly working ELPA
compiled with the AVX512 support (I went for the latest elpa-
2018.11.001 version), it just returns bogus results and diverges after
few iterations. If someone has this working I'd be really grateful for 
a working configure line, and advice with which elpa and which compiler
version this was.

Unfortunately I was not able to get any support from the cluster admins
beyond "We see a 30% per-core performance increase in average"
therefore asking here if anyone has experience with such machines.

Any advice would be appreciated.
Best regards
Pavel