[CP2K:6011] Improve the speed of QS in cp2k

[Iain Bethune]

Dear Geng,

There are a couple of areas to consider when you are interested in performance, firstly the physics (which others will be more able to comment on), and secondly, computational.

Physical parameters:
* choosing the cheapest representation of your system that gives correct results e.g. choosing an appropriate basis set (Gaussian), and also an appropriately sized plane-wave expansion (see http://www.cp2k.org/howto:converging_cutoff )

* SCF settings - choosing an appropriate convergence threshold, and diagonalization algorithm (or use OT for non-metallic systems for much greater performance, with a good preconditioner) see http://www.cp2k.org/howto:static_calculation for some of the basics

Computational aspects:
* If you are running in parallel with MPI do some tests (on a shortened version of your problem) to determine how many CPU cores you can effectively use.  As a rule-of-thumb, you might expect reasonable scaling up to nprocs ~ natoms for typical settings.  see http://cp2k.org/performance and http://www2.epcc.ed.ac.uk/~ibethune/files/cp2k_cug2014.pdf for benchmark data.

* Build the code with high compiler optimisation (e.g. -O3) and an optimised BLAS/LAPACK library (e.g. MKL, GotoBLAS, ATLAS)

* Build the code with the optional performance-critical libraries libsmm (in cp2k/tools/build_libsmm) and libgrid (cp2k/tools/autotune_grid).

Before going to far down any of these areas, take a look at the timing report which is printed at the end of your CP2K job output.  This will give you some information about which parts of the code are taking the most time, and therefore where to invest your time tweaking to get the best performance.

Cheers

- Iain

--

Iain Bethune
Project Manager, EPCC

Email: ibet... at epcc.ed.ac.uk
Twitter: @IainBethune
Web: http://www2.epcc.ed.ac.uk/~ibethune
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> On 16 Jan 2015, at 13:32, sungen... at gmail.com wrote:
> 
> 
> Hello, evergyone 
> 
>    Could anyone give any generic comments on how to improve the DFT ( I mean the speed), 
>    calculations in cp2k.
> 
>    I want to use the cp2k studying surfaces of metals or oxides.  I read the documents , and I can run the structure optimization successfully,
>    But too many parameters for consideration.  I want to know if any parameter is the most important, and it's need carefully to be tested.
> 
>  Thanks !
> 
> Geng Sun
> 
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