[Difx-users] Difx on XEON Scalable Platform CPUs?

[Richard Dodson]

Hi Walter

 When I had DiFX running on early versions of Xeon Phi (2012?) I had to
by-pass the IPP libraries (at the time Intel said they were not keen to
carry those forwards). So all functionality was included in GENERIC. Some
things had to be inline functions, but I could use the MKL libraries for
others.
Has IPP been ported now?


 If not (and maybe if so) it could be worth looking to see where the speed
up would be (it was dominated by the complex multiply accumulate at the
time) and see if that could be improved. For example the intrinsic for
genericAddProduct_32fc
could be replaced with the code example in:

In https://software.intel.com/en-us/forums/intel-isa-extensions/topic/74737

 The comments include:

SSE3 (included in SSE4.2) has specific instructions which the compiler will
use to vectorize complex without requiring intrinsics or shuffle.  In order
to use fully AVX2 or AVX512, as John said, it will be necessary to split
the data. Compilers will not attempt to evaluate whether a mixture of SSE3
and AVX2 will prove faster.  The statistics produced by opt-report may help
to evaluate this, and might lead you to use some SSE3 intrinsics in case
the overhead of splitting the data would be significant.


Page 5-26 of
https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
may have useful examples as well

       Richard

On Tue, Apr 10, 2018 at 9:20 AM, <Chris.Phillips at csiro.au> wrote:

> Hi Walter
>
> No I haven’t, but just a note that when I tried DIFX  on the
> KnightsLanding an year or so ago, IPP had not been ported to AVX512 at that
> stage
>
> Cheers
> Chris
>
>
>
> > On 10 Apr 2018, at 11:15, Walter Brisken <wbrisken at lbo.us> wrote:
> >
> >
> > Hi DiFX Users,
> >
> > I'm wondering if anyone on this list has tried DiFX on Intel XEON CPUs
> called "Scalable Platform".  These are distinguished by "bronze", "silver",
> "gold", or "platinum" varieties.  They are also labeled as "Skylake-SP"
> processors.  If anyone has such experience, I'm wondering if any benchmarks
> are available.  Also wondering if any attempt to evaluate improvement the
> AVX512 instructions offer in DiFX computing.
> >
> > Thanks,
> >
> > Walter
> >
> > --
> > -------------------------
> > Walter Brisken
> > Director
> > Long Baseline Observatory
> > (575)-835-7133 (office)
> > (505)-234-5912 (cell)
> >
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-- 
-------------------------
Dr Richard Dodson,
International Centre for Radio Astronomy Research
University of Western Australia
P: +8 6488 7842 E: richard.dodson at icrar.org
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