[Wien] Speed of cluster nodes

[Peter Blaha]

For your problem, you just need to reduce the Energy window in case.inso 
when you do the fine k-mesh (no scf with this k-mesh).
Make sure, your emin does not cut bands, but falls in a "gap".

Usually, all k-points take the same time (within 10 % or so).
It looks more as if one node is (temporarely) overloaded or has network 
(disk) problems.
Try to check it by logging into this node and use eg. "top".


Am 10.11.2023 um 18:53 schrieb pluto via Wien:
> Dear Prof. Blaha, dear All,
> 
> Thank you for you comment. When changing numbers as you suggested the 
> convergence over few cycles didn't look very good. So I decided to redo 
> the calculation with init_lapw -prec 1 -ecut 0.999, I think this is 
> safer and I hope the files will be smaller. Once this is done, I will 
> try to reduce emax in case.inso.
> 
> The origin of the problem is that I would like to make a kx-ky mesh for 
> the slab, this means maybe 2000-3000 kpoints to see bands as surfaces 
> nicely. Then the output files become very large, and case.qtl files are 
> large too (I typically do a SOC and FM calculation). One can limit the 
> energy range in case.inq to e.g. from -1 to 1, but this sometimes (for 
> unknown reasons) leads to some counting issues of the bands, i.e. 
> different k-points have different bands order. This might be related to 
> the lower energy cutting though a band, but some time ago I tried 
> different ranges in case.inq and it was not very helpful (but I need to 
> try more). Anyway, not a big deal, in the end this can be sorted out in 
> many ways. In general most of the time I only need bands from say -10 to 
> 10 eV around the Fermi level, so in general it is good to learn how to 
> calculate only that, perhaps increasing the calculation speed and 
> reducing the output file sizes.
> 
> Another question: I often run on the older cluster. All nodes should be 
> the same and I distribute k-points uniformly (e.g. 8 k-points per node). 
> I noticed that sometimes some nodes are calculating much slower (e.g. 
> lapw1 or lapwso) than other nodes. Is that normal? I would expect maybe 
> small fluctuations due to the particular CPU cooling efficiency etc., 
> but nothing dramatic. Or perhaps sometimes some k-points need more time?
> 
> Best,
> Lukasz
> 
> 
> On 2023-11-07 18:42, Peter Blaha wrote:
>> I'm not quite sure what you mean.
>>
>> restore your saved calculation and:
>> i)  Reduce emax in case.inso
>> This reduces the size of case.vectorso, but has no influence on the
>> scf. (One iteration is enough).
>> ii) reduce Ecut in case.in1.  However, this will make your spinorbit
>> calculation much less accurate. You need to run the scf, but it should
>> converge quicker .
>>
>> Am 07.11.2023 um 18:26 schrieb pluto via Wien:
>>> Dear All,
>>>
>>> I have a larger FM-SOC calculation converged (and saved) with the 
>>> default Ecut.
>>>
>>> I would like to converge with smaller Ecut (say 1 Ry), to have the 
>>> output files smaller.
>>>
>>> Is there a good way to do this, using the converged one as a starting 
>>> point, to avoid the lenghty convergence?
>>>
>>> Best,
>>> Lukasz
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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