[Nek5000-users] libxsmm within Nek5000

[nek5000-users at lists.mcs.anl.gov]

Let me add some more comments about this:

NekBox implements three tuned high-levels operators:
- opgrad
- interpolation
- axhelm

Note, in a typical production the time spend axhelm dominates (25-45% of the total runtime) where the other two are around 5% in total. From what I recall they managed to get a speedup of 1.5x for axhelm (lx1=8) compared to Nek5000 default implementation. This suggests that the overall speedup for lx1=8 is about 10-20% at most. Having this in mind I didn't explore it further because it doesn't buy you much. 

Cheers,
Stefan

-----Original message-----
> From:nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
> Sent: Monday 20th November 2017 14:00
> To: nek5000-users at lists.mcs.anl.gov
> Subject: Re: [Nek5000-users] libxsmm within Nek5000
> 
> At the moment there are no tuned "high-level "operators like axhelm(). Also my experience is that libxsmm is faster for lx1>14 which is rarely used for production runs.
> 
> Cheers,
> Stefan
> 
> -----Original message-----
> > From:nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
> > Sent: Monday 20th November 2017 13:49
> > To: nek5000-users at lists.mcs.anl.gov
> > Subject: [Nek5000-users] libxsmm within Nek5000
> > 
> > Hi,
> > 
> > Do you have any performance results of the libxsmm comparing with stand-alone "mxm" ?
> > 
> > In the master branch of Nek5000, the libxsmm function "libxsmm_dgemm" is only called in file "
> > mxm_wrapper.f"
> > ...
> > #ifdef XSMM
> >          call libxsmm_dgemm('N','N',n1,n3,n2,1.0,a,n1,b,n2,0.0,c,n1)
> > #endif
> > ...
> > 
> > I could not find any optimization works such as dispatch and streaming updates in the kernels that were used in e.g. NekBox.
> > 
> > What is the status about the implementation of libxsmm or other SIMD techniques within Nek5000 right now?
> > 
> > Thanks. /Jing 
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