[QE-developers] DFTI and OpenMP detection in configure

[Ye Luo]

I got a bit confused. When you say FFTW, did you it mean the FFTW3 library
or the internal FFTW shipped with QE?

DFTI vs FFTW3 on intel platforms
Intel claimed comparable performance using DFTI and FFTW3 interfaces
provided by MKL.
But QE with DFTI outperforms FFTW3 in both absolute performance and thread
salability.

I never did a comparison between MKL DFT and fftw.org FFTW3 on Intel
platforms.

Best,

Ye
===================
Ye Luo, Ph.D.
Computational Science Division & Leadership Computing Facility
Argonne National Laboratory


Lorenzo Paulatto <paulatz at gmail.com> 于2019年9月16日周一 上午4:18写道：

> Ok, I answer to myself: using DFTI with openmp causes mysterious
> problems usually using diagonalization. Do you know if using the Intel
> FFTW interface would work around these or if it is exactly the same
> thing? Because, the little bit of scalability that I can gain from
> openmp is exactly lost by the performance I loose with FFTW3 wrt DFTI...
>
> cheers
>
> On 16/09/2019 10:30, Lorenzo Paulatto wrote:
> > Hello,
> > I have noticed that the configure script detects and enables
> > automatically the DFTI FFT libraries when executed without any specific
> > switch, but that it uses FFTW instead when executed with the
> > --enable-openmp switch.
> >
> > I was wondering if this is intentional (i.e. because FFTW can give
> > better performance with openmp? Or DFTI does not work with openmp?) or
> > it is a bug.
> >
> > cheers
> >
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
> phone: +33 (0)1 442 79822 / skype: paulatz
> <http://www.impmc.upmc.fr/~paulatto/> <http://sf.net/p/d3q>
> 23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
>
> --
> Lorenzo Paulatto - Paris
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