[CP2K:10705] Performance of cube file writing with MPI I/O

[Nico Holmberg]

Hi Ondrej,

I just committed a patch 
<https://github.com/cp2k/cp2k/commit/b91fef267be208dd1fc4bc2acadc259e97af108c> 
which adds an input option to disable MPI I/O. Starting from SVN revision 
18601, you can set the value of the flag ENABLE_MPI_IO to FALSE in the 
GLOBAL <https://manual.cp2k.org/trunk/CP2K_INPUT/GLOBAL.html> input section 
if you want to disable MPI I/O.

I opened up an issue on the Github issue tracker 
<https://github.com/cp2k/cp2k/issues/16>, where you can find small 
benchmark input files for testing the effects of MPI I/O on cube file 
writing/reading performance. You can also find my benchmark results from 
two different machines there. Feel free to run the benchmark tests and 
report your timings.


BR,

Nico 

sunnuntai 9. syyskuuta 2018 22.04.17 UTC+3 Ondřej Maršálek kirjoitti:
>
> Hi Nico, 
>
> thanks for looking into this. I thought I could at least disable it 
> for now by hardcoding `parallel_write = .FALSE.` (not letting it be 
> overwritten based on `mpi_io`) in `pw_to_cube`, but that apparently 
> does not work, it fails later at `CPASSERT(checksum == 1)` (line 150 
> in 6.1). I'd be happy to provide benchmark numbers for a suitable test 
> case that show the slowdown, let me know if you'd like those. 
>
> Best regards, 
> Ondrej 
>
> On Sun, Sep 9, 2018 at 9:08 AM Nico Holmberg <holm... at gmail.com 
> <javascript:>> wrote: 
> > 
> > Hi, 
> > 
> > My experiences were totally opposite, which is why I made it the default 
> option. Give me a couple of days and I'll add an input option to disable 
> it. 
> > 
> > BR, 
> > 
> > Nico 
> > 
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