[QE-users] D3Q code stopped due to davcio error

[Lorenzo Paulatto]

> Thanks for pointing out the storage issue. Yes, I am running it at the 
> French computing centre (University of Bordeaux's cluster system 
> (curta, mcia)). Here I am attaching the d3q output file. Indeed, it 
> was in the process of computing the second q-point triplet.

I do not have access to  Bordeaux cluster, but I could ask it if you 
need that I look at the code. That said, I see that to compute the first 
q-point it took about 5 days, it will take at least a month to do the 
second point ! Because it has less symmetry the code needs to compute 2x 
more k-points and 3x more perturbations.

>
> "Maybe for such a large system you can get some decent force-constants 
> already from (0,0,0) alone"
>
>
> In that case, you mean to implement the "mode=gamma-only" tag?
>
Not really, the triple (0,0,0) is in itself the 1x1x1 grid, and you can 
threat it as such. Thanks to some Fourier interpolation trickery, you 
can use it to get the D3 matrices at any point. Also, the d3_qq2rr code 
is not particularly optimized, and is not parallelized I'm not sure you 
would manage to compute the Fourier transform of the 2x2x2 grid anyway.

You have to keep in mind that the 3-body force constant become huge very 
quickly with the number of atoms and the size of the grid: each D3 
matrix has (3*nat)^3 complex elements, and a grid n x n x n  contains 
n^6 power triplets

In your case, the 2x2x2 grid would use about 2.2GB of RAM, which is 
probably still feasible, but i would try the 1x1x1 first.


cheers

>
>
> Regards,
>
> Kanka
>
>
>
>
>
> Kanka Ghosh
> Postdoctoral Researcher
> I2M-Bordeaux
> University of Bordeaux, CNRS UMR 5295
> Site: Ecole Nationale Supérieure des Arts et Métiers
> Bordeaux-Talence 33400
>
> ------------------------------------------------------------------------
> *From: *"Lorenzo Paulatto" <paulatz at gmail.com>​_
> *To: *"users" <users at lists.quantum-espresso.org>
> *Sent: *Thursday, December 3, 2020 11:23:58 PM
> *Subject: *Re: [QE-users] D3Q code stopped due to davcio error
>
>      task #        71
>
>          from davcio : error #      5011
>          error while writing from file
>     ".//D3_Q1.0_0_0_Q2.0_0_-1o2_Q3.0_0_1o2/scf.d1.dq1pq1.72"
>
>
> I guess it may have run out of space, d3q uses a ton of disk space and 
> there is not easy way to avoid this. If you are running on any of the 
> French computing centers I can try to have a look directly.
>
> I do not think the change in number of CPUs could cause this problem, 
> but if you provide the full output I can check. Also, 44 atoms is a 
> lot for the d3q code, it seems like you're running the second q-point 
> triplet, which is of kind (0,q,-q), it takes much more time and disk 
> space than the triplet (0,0,0). Maybe for such a large system you can 
> get some decent force-constants already from (0,0,0) alone
>
> cheers
>
>
>     Kanka Ghosh
>     Postdoctoral Researcher
>     I2M-Bordeaux
>     University of Bordeaux, CNRS UMR 5295
>     Site: Ecole Nationale Supérieure des Arts et Métiers
>     Bordeaux-Talence 33400
>
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