[Wien] .machines for several nodes

[Peter Blaha]

Please study the syntax for the .machines files.

Only dstart, lapw0 or nlvdw have specific   program:xxx entries.

The lapw1/2 parallelization is done via lines like:

speed:hostname:nodes

So you need a line like:

1:g008:4 g021:4 g025:4 g028:4

This would span ONE lapw1/2 jobs with mpi on 16 cores

alternatively, if you want k-parallelism, lines like

1:g008:4
1:g021:4
1:g025:4
1:g028:4

should do 4 k-parallel jobs, each running with 4 mpi-tasks.

However, since mpi diagonalization may have some overhead compared to 
sequential lapw1/2 (in particular when using SCALAPack and not ELPA), an 
alternative is to use k-point + omp parallelization:

1:g008
1:g021
1:g025
1:g028
omp_global:4
omp_lapw0:1

Regards


On 10/12/20 9:06 AM, Christian Søndergaard Pedersen wrote:
> Hello everybody
> 
> 
> I am new to WIEN2k, and am struggling with parallellizing calculations 
> on our HPC cluster beyond what can be achieved using OMP. In particular, 
> I want to execute run_lapw and/or runsp_lapw running on four identical 
> nodes (16 cores each), parallellizing over k points (unless there's a 
> more efficient scheme). To achieve this, I try to mimic the example from 
> the User Guide (without the extra Alpha node), but my .machines-file 
> does not work the way I intended. This is what I have:
> 
> 
> #
> 
> dstart:g008:4 g021:4 g025:4 g028:4
> 
> lapw0:g008:4 g021:4 g025:4 g028:4
> 
> lapw1:g008:4 g021:4 g025:4 g028:4
> 
> lapw2:g008:4 g021:4 g025:4 g028:4
> 
> granularity:1
> 
> extrafine:1
> 
> 
> The node names gxxx are read from SLURM_JOB_NODELIST in the submit 
> script, and a couple of regular expressions generate the above lines. 
> Afterwards, my job script does the following:
> 
> 
> srun hostname -s > slurm.hosts
> run_lapw -p
> 
> which results in a job that idles for the entire walltime and finishes 
> with a CPU efficiency of 0.00%. I would appreciate any help in figuring 
> out where I've gone wrong.
> 
> 
> Best regards
> Christian
> 
> 
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-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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