[QE-developers] Code divergence

[Paolo Giannozzi]

Hi Ye, we know quite well the "divergence" problem you mention, much less
about the solutions. If you have good ideas, or just ideas, feel free to
propose them. For GPU's, we are trying to isolate strongly GPU-specific
parts. For mixed precision, we are at preliminary tests.

I perfectly agree about unit testing, at least for those parts of QE for
which it is suitable. For instance: FFTXlib has already some unit tests;
LAXlib could have some; for KS_Solvers, it's not going to be easy. It
should also be easy to set up unit tests for exchange-correlation
functionals and for symmetry-related stuff.

Paolo

On Sun, Jul 29, 2018 at 4:06 AM, Ye Luo <xw111luoye at gmail.com> wrote:

> Hi developers,
>
> Many features currently under development are getting QE ready for the
> future. This is very encouraging.
> However, I feel the code is diverging and needs attention.
> The upcoming GPU code is basically an internal fork with large amount of
> lines duplicated.The mixed precision attempt also duplicates functions.
> QE already has gamma/k or complex/real forks inside the code. The more
> forks added to the code, the more needed maintenance and potential bugs.
>
> Although fortran has its language limitation, some design choices may help
> reducing the complexity. Having one binary is appealing but allowing
> building multiple binaries and fixing precision at compile time to minimize
> the lines of duplicated code is more beneficial long term.
> The CPU/GPU gap may have a chance to get closed by performance portable
> solutions although the software stack is not matured especially on the
> fortran side at the moment.
>
> It is very challenging and the manpower is often limited. Although the
> reality is often a compromise, I believe QE developers figure out the best
> way.
>
> One more thing, testing is very important. Although there are some tests
> but more tests are needed not only integration tests but also unit tests.
>
> Best,
> Ye
> ===================
> Ye Luo, Ph.D.
> Leadership Computing Facility
> Argonne National Laboratory
>
> _______________________________________________
> developers mailing list
> developers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/developers
>
>


-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/developers/attachments/20180806/80612e2c/attachment.html>