[CP2K-user] [CP2K:13950] Re: gas phase calculations

[Pierre Cazade]

Dear Marcella,

Please find as attached document two output files. The first aco-mo.inp 
contains the results for a crystal made of 78 atoms. This is a normal 
condensed phase calculation. The second opt.out is for the gas phase 
system made of 75 atoms. The systems have nothing in common.

I would like to attract your attention that the grid cutoffs of 
aco-mo.inp are much larger than those of opt.inp, and yet aco-mo.inp is 
much faster than opt.inp.

I am also running the gas phase system on a single node of a cluster 
with 40 MPI tasks. The calculation is obviously faster than on my 
workstation but still frustratingly slow.

Regards,
Pierre

On 22/09/2020 14:00, Marcella Iannuzzi wrote:
> Dear Pierre,
>
> from the timings in the output you should be able to determine where 
> the calculation is spending most of the time and compare to the 
> condensed matter calculation. Most probably OMP is not the most 
> efficient in this case to parallelise. Have you tried with 8 tasks 
> instead.
> Regards
> Marcella
>
>
> On Tuesday, September 22, 2020 at 1:53:36 PM UTC+2 
> pier... at gmail.com wrote:
>
>     Hi Marcella,
>
>     I am trying to run the calculation on my workstation with just OMP
>     (8 threads). This usually works for condensed phase with a two
>     hundred atoms so I thought it would be fine for just 75 atoms.
>     Anyway, I reduced the cutoffs and it seems to be helping a lot but
>     it is still slow and require a lot of memory. Please find as
>     attached document the input file I am using.
>
>     Regards,
>     Pierre
>
>
>     On 22/09/2020 11:06, Marcella Iannuzzi wrote:
>>     Dear Pierre,
>>
>>     Without additional information, like input, output, scaling with
>>     the number of processors ...,
>>     it is not possible fo provide any help.
>>     Regards
>>     Marcella
>>
>>
>>     On Monday, September 21, 2020 at 1:09:03 PM UTC+2
>>     pier... at gmail.com wrote:
>>
>>         Dear CP2K users,
>>
>>         I would like to know how to perform a gas phase calculation
>>         with CP2K. I tried to follow some of the examples available
>>         in the tutorials but they lead to very slow and heavy
>>         calculations for a system with only 75 atoms.
>>
>>         I used wavelet for the Poisson solver, I set periodic none
>>         for both the solver and the cell. The cell is cubic with a
>>         size of 26.250 A. I am using DFT (PBE) with OT. Should the
>>         number of grid be changed compared to a condensed phase? What
>>         about the cutoffs?
>>
>>         Alternatively, I tried the periodic approach with a larger
>>         cell so that the molecule "does not interact" with its
>>         periodic image .Yet again, the calculation is extremely
>>         demanding in terms of memory which makes the OS kill the job.
>>
>>         Is there a solution to these problems?
>>
>>         Regards,
>>         Pierre
>>
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>
>     -- 
>     Dr Pierre Cazade, PhD
>     AD3-023, Bernal Institute,
>     University of Limerick,
>     Plassey Park Road,
>     Castletroy, co. Limerick,
>     Ireland
>
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-- 
Dr Pierre Cazade, PhD
AD3-023, Bernal Institute,
University of Limerick,
Plassey Park Road,
Castletroy, co. Limerick,
Ireland

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