[Wien] Wien2k on AVX512 CPUs

Peter Blaha pblaha at theochem.tuwien.ac.at
Wed Feb 27 10:24:08 CET 2019


That's exactly what I said:

The current WIEN2k_18 release cannot be used with ELPA versions more 
recent than 2017.
And I don't think that ELPA-2015 had AVX512 support.

On 2/27/19 10:14 AM, Laurence Marks wrote:
> N.B., there was an seclr4 update posted some time ago, I think by Thomas 
> Ruh. This may be needed, and may not be in the current Wien2k release on 
> the web page.
> 
> The next release will do a better job I suspect.
> 
> _____
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what 
> nobody else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> 
> On Wed, Feb 27, 2019, 03:07 Laurence Marks <L-marks at northwestern.edu 
> <mailto:L-marks at northwestern.edu> wrote:
> 
>     I think Peter may have mispoke about the latest elpa. I believe it
>     will run OK if you compile it (--enable-AVX512 etc) so the highest
>     kernel is equal to the lowest instruction set you use. You may also
>     get it to work by using their environmental variables. With the
>     current Wien2k you cannot exploit elpa optimally if you have a
>     heterogeneous set of nodes.
> 
>     I would say 30% faster comparing a 6130 to a E5-2650. However, ifort
>     compiler switches can make a big difference, as can the mpi version.
> 
>     N.B., I can dig up my elpa compiler options later if needed. I use
>     ifort/icc/mpiifort/mpiicc.
> 
>     _____
>     Professor Laurence Marks
>     "Research is to see what everybody else has seen, and to think what
>     nobody else has thought", Albert Szent-Gyorgi
>     www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> 
>     On Wed, Feb 27, 2019, 02:50 Peter Blaha
>     <pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>
>     wrote:
> 
>         We have an Intel I7-7820X CPU @ 3.60GHz with 8 cores and avx512.
> 
>         The testcase with OMP_NUM_THREADS=1 runs a bit faster with
>         avx512 than
>         with avx2, but it is a rather small effect (at least when
>         working with
>         this MKL_ENABLE_INSTRUCTIONS variable:
>         ----------------------avx512
>                  TIME HAMILT (CPU)  =     5.1, HNS =     2.1, HORB =   
>           0.0,
>         DIAG =    15.3
>                  TIME HAMILT (WALL) =     5.4, HNS =     2.1, HORB =   
>           0.0,
>         DIAG =    15.3
>         ----------------------avx2
>                  TIME HAMILT (CPU)  =     5.8, HNS =     2.5, HORB =   
>           0.0,
>         DIAG =    16.3
>                  TIME HAMILT (WALL) =     6.1, HNS =     2.5, HORB =   
>           0.0,
>         DIAG =    16.3
> 
>         However, when using OMP_NUM_THREADS=8, this difference is further
>         reduced (probably due to memory bounds ?)
>         -----------------------avx512
>                  TIME HAMILT (CPU)  =    19.9, HNS =     7.7, HORB =   
>           0.0,
>         DIAG =    24.2
>                  TIME HAMILT (WALL) =     2.6, HNS =     1.0, HORB =   
>           0.0,
>         DIAG =     3.2
>         ------------------------avx2
>                  TIME HAMILT (CPU)  =    20.0, HNS =     7.4, HORB =   
>           0.0,
>         DIAG =    27.0
>                  TIME HAMILT (WALL) =     2.6, HNS =     1.0, HORB =   
>           0.0,
>         DIAG =     3.5
>         -------------------------------------------------------------------------
> 
>         Yes, we have the latest ELPA elpa-2018.11.001 installed. Seems
>         to run
>         without problems and is overall significantly better than the
>         old ELPA),
>         but it requires a change in the user interface. The next release of
>         WIEN2k will have two elpa versions supported, a ELPA15 (which is in
>         WIEN2k_18), and a new ELPA interface for elpa versions later
>         than 2017
>         (this is somehow like FFTW2 and FFTW3 versions).
> 
>         So in essence: with the present code one cannot use
>         ELPA-versions from
>         2017 or later.
> 
>         On 2/27/19 7:34 AM, Pavel Ondračka wrote:
>          > 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
>          >
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>         -- 
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>                                                 P.Blaha
>         --------------------------------------------------------------------------
>         Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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-- 

                                       P.Blaha
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