[CP2K-user] [CP2K:14812] Scaling with xTB

[Manjusha Chugh]

Dear Mauro,

yes, but I just meant a general way of reporting time in computations.

Anyway, as suggested by Fabian, using square number of cores helps.
And for my more than 1000 atoms system, scaling in xTB is as follows:
cores    time_per_MD_step
100           4
144           3

Regards
Manjusha


On Mon, Feb 22, 2021 at 11:51 AM Mauro Sgroi <maurofran... at gmail.com>
wrote:

> Dear  Manjusha,
> If I understand well, the time per MD step should correspond to the times
> that I'm reporting divided by 100.
>
> Dear Fabian,
> Thanks a lot for the information. I will check the use of 25 cores instead
> of 28. I'm using 28 since our nodes have 28 cores each.
>
> Is this scaling the related to the xTB method or is it linked to its
> current implementation on CP2K? Can the linear scaling approach improve the
> situation?
>
> Thanks a lot and best regards,
> Mauro.
>
> Il giorno lunedì 22 febbraio 2021 alle 11:44:24 UTC+1 fa... at gmail.com
> ha scritto:
>
>> Dear Mauro,
>>
>> This is consistent with my own observations of the scaling of xTB.
>> Because of the increasing cost of communication more CPUs don't necesarily
>> speed up the simulation. I don't use more than 25 CPUs with xTB unless I
>> have well above 1000 atoms.
>>
>> Please note that the number of MPI ranks should be a square number. 25
>> CPUs are probably faster than 28 unless you are using k-points.
>>
>> Cheers,
>> Fabian
>>
>> On Monday, 22 February 2021 at 11:10:11 UTC+1 chu... at gmail.com wrote:
>>
>>> Hi Mauro,
>>>
>>> it will be easy to look into your scaling issue if you report time for
>>> each MD step. I am also doing MD with xTB.
>>>
>>> Regards
>>> Manjusha
>>>
>>>
>>> On Mon, Feb 22, 2021 at 10:59 AM Mauro Sgroi <mauro... at gmail.com>
>>> wrote:
>>>
>>>> Dear all,
>>>> I'm testing the xTB code on a liquid electrolyte containing a Li ion.
>>>> I'm running MD on a cell containing 728 atoms.
>>>> I obtain a disappointing scaling with the number of cores. The
>>>> following are times for 100 MD steps:
>>>>
>>>> cores  Time (s)
>>>> 28         7818
>>>> 56         7364
>>>> 84         6529
>>>> 112       7493
>>>>
>>>> My input file can be downloaded here:
>>>>
>>>>
>>>> https://drive.google.com/file/d/1KvZz5x6FwgOP3dzH6fePghMQBineIlfE/view?usp=sharing
>>>>
>>>> Is this the right behaviour to be expected? Or is there is something
>>>> wrong in my compilation of the code or in the input file?
>>>> The HPC facility has a Infinband network protocol and a fast shared
>>>> filesystem.
>>>>
>>>> Thanks a lot in advance and best regards,
>>>> Mauro Sgroi.
>>>>
>>>>
>>>>
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