[Pw_forum] Off-topic: parallel compilation

[Giuseppe Mattioli]

Dear Marcos
I've performed up to 200-atom calculations by using B3LYP and HSE. Not on a PC of course, but on not so powerful facilities... There are a couple of 
things you can try before quitting.

1) Start with the minimal setup. Si PPs are usually not very hard, even NC ones should be safely used at ecutwfc=40.0. Try a first calculation such as

    ecutwfc=40.0,
    ecutfock=40.0, !!!Spectacular speedup with this...!!!
    nqx1 = 1, nqx2 = 1, nqx3 = 1,

    conv_thr=1.0d-6
    adaptive_thr=.true.

K_POINTS {gamma}


2) The lower cutoff on density used for Fock integrals is a spectacular time-saving, very nice trick. ecutfock=ecutwfc is the minimal value, but you 
usually (in my experience) find convergence around ecutfock=2*ecutwfc, that is, still quite far from the default ecutfock=ecutrho value.

3) Starting from the "gamma" results, try a second calculation by using a low symmetry K-point, usually a good choice for a "decent" geometry 
optimization. This should be still affordable without problems.

K_POINTS {automatic}
1, 1, 1, 1, 1, 1

4) Try something more expensive (only scf+forces, to check that everything is OK). The final setup depends on what you are interested in (interaction 
with molecules, a decent DOS, surface defects...), but remember that band structures are not affordable in the EXX framework.

HTH

Giuseppe

On Sunday 18 May 2014 18:22:49 Marcos Veríssimo Alves wrote:
> Dear Pang and Paolo,
> 
> Thanks a lot for your comments. Since this is likely not a problem of the
> 32-bit integers, I suppose I'll have to resort to a HPC facility then. Back
> to re-compiling espresso with the 32-bit interface :)
> 
> Best regards,
> 
> Marcos
> 
> 
> On Sun, May 18, 2014 at 12:25 PM, Paolo Giannozzi
> 
> <paolo.giannozzi at uniud.it>wrote:
> > IMHO the most likely reason for the crash is insufficient memory,
> > not insufficient size of 32-bit integers. A few occurrences of the
> > latter have been encountered and fixed in the past, but only on
> > very large cells
> > 
> > P.
> > 
> > On Sun, 2014-05-18 at 11:10 -0300, Marcos Veríssimo Alves wrote:
> > > Hi all,
> > > 
> > > 
> > > This is a bit off-topic, but I'm sure there will be many knowledgeable
> > > people around. It's related to the parallel compilation of QE.
> > > 
> > > 
> > > I'm trying to run HSE calculations for a 71-atom silicene sheet, using
> > > Espresso compiled with ifort (composerxe), mpich2 and intel mkl
> > > included in this version of the compiler. Mpich 2 is compiled using
> > > gcc/ifort.
> > > 
> > > 
> > > All goes well in the scf part until it gets to the hybrid functional
> > > calculation. Then it crashes with an mpi error (Bad termination, code
> > > 9) which the mpi faq says is usually due to the fact that there is a
> > > segmentation fault in the code, not in mpi.  They also state that this
> > > is usually a segmentation fault.
> > > 
> > > 
> > > I wonder if anyone has run HSE calculations for systems as large as
> > > this, and if they have run into this problem.
> > > 
> > > 
> > > One possibility that came to my mind is that, if this is a
> > > segmentation fault, maybe 4-byte integers are not large enough to
> > > address all the indexes of the arrays allocated in the hybrid
> > > functional part of the calculation. I tried to compile QE with 8-byte
> > > integers but I get an mpi error, which I suppose is due to integers
> > > being compiled with 4-byte integers on the C side of the compilation.
> > > 
> > > 
> > > So, I have two questions:
> > > 
> > > 
> > > 1) Is there any way of compiling Mpich 2 with 8-byte integers using
> > > gcc?
> > > 
> > > 
> > > 2) If the parallel part were carried out with OpenMP instead of Mpich
> > > (I have 32 cores in the same node of the computer I'm running the
> > > calculation), perhaps this could be a workaround for this problem. Is
> > > it possible to compile QE in parallel mode using only OpenMP and MKL?
> > > If yes, what options would need to be set for either configure or
> > > make.sys directly? Configure already detects the mpi environment, and
> > > sets make.sys to compile QE using it.
> > > 
> > > 
> > > Any help would be greatly appreciated, and I would gladly supply the
> > > input file along with the pseudo I am using (from the QE database) if
> > > the developers would like to run tests on it.
> > > 
> > > 
> > > Best regards,
> > > 
> > > 
> > > Marcos
> > > 
> > > 
> > > _______________________________________________
> > > Pw_forum mailing list
> > > Pw_forum at pwscf.org
> > > http://pwscf.org/mailman/listinfo/pw_forum
> > 
> > --
> > Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> > Phone +39-0432-558216, fax +39-0432-558222
> > 
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://pwscf.org/mailman/listinfo/pw_forum


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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
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