Thanks for the explanation. That was really helpful. -Madhura
> > Dear Madhura, > >> >> Thanks for the explanation. >> I had always thought that DOS code also requires wavefunction files; >> and >> that is why one needs to give the same prefix and outdir path as in scf >> calculations. If code does not need wavefunctions, which files it uses >> for DOS calc.s? > > the code needs mainly the eigenvalues, which are stored in > $prefix.save/K?????/eigenval.xml files, > where K????? (i.e. K00001, K00002, etc ) correspond to each kpt. > > >> As per suggestion, I have run PDOS calc.s with the same number of pools >> and processors (in case of B) and got results. That means PDOS code is >> parallelized with pool implementation, but not DOS. >> > > yes you are right, > this means that pDOS is parallelized over G vectors and pools, while > DOS calculation is not parallelized but is anyway compatible with > the parallel environment (i.e. it does not crash if run parallel) > > andrea > >> Thanks once again, >> Madhura. >> >> > >> > Dear Madhura, >> > >> > the issue of using the same parallelism scheme (# of processors, # of >> > pools, etc) in postprocessing calculations is mainly concerned with >> the >> > need to read wfcs. As you wrote, if you specify wf_collect = .TRUE. >> you >> > completely remove this issue (you can read wfcs whatever the >> > parallelization >> > scheme you used to produce them). >> > >> >>From this point of view, the main difference between DOS and pDOS >> > calculations is that the former does not need to read wfcs, while the >> > latter does. >> > >> > Moreover, the taks the DOS program has to perform is so inexpensive >> that >> > it is performed by a single processor even if the code is run in >> parallel. >> > This is consistent with your observation at (ii). >> > >> > In the case of pDOS (i.e. when running projwfc.x) if you do not >> collect >> > wfcs you should run with the same # of processors and the same pool >> > parallelism. Otherwise, as you experienced, you get a davcio error >> > (some of the wfcs files were not found). >> > According to me, anyway, projwfc should work with pools if the above >> > conditions are fulfilled. >> > >> > hope it helps >> > andrea >> > >> > >> >> >> >> There have been many discussions in this forum about parallelization >> of >> >> DOS and projected DOS codes. However, some of the points were not >> clear >> >> to >> >> me, so I have performed some scf calculations for a very simple >> system >> >> using 8 processors and with flag wf_collect 'false'. I have performed >> >> same >> >> calculations once without use of pools (A) and then using 2 pools >> (B). >> >> Then using theses wavefunctions I have performed DOS and PDOS >> >> calculations. Following is the summary of results and my >> interpretation: >> >> >> >> i) Pool parallelization is not implemented for both these codes. >> >> >> >> ii) DOS calculations: for both the cases A and B, one can calculate >> DOS >> >> with the same no. of processors (= 8) and the results match within >> >> numerical errors; even though for case B, the wavefunctions were >> >> obtained >> >> with pooling and DOS without it. >> >> For case A, even if I use 4 processors I get identical results as >> when >> >> I >> >> use 8 processors. (Note, I have not checked with less no. of proc.s >> for >> >> B). >> >> => The condition that we need the same no. of processors and pools as >> >> were >> >> used in scf calculations is not necessary; and it is possible to get >> DOS >> >> results even with wavefunctions generated with pool parallelization. >> >> >> >> iii) PDOS calculations: This can be calculated only in case of A and >> >> using >> >> the same no. of processors. If I use wavefunctions generated in case >> B >> >> or >> >> less no. of processors (= 4) with A wavefn.s then I get "davcio" >> error. >> >> => >> >> For PDOS calculations, one cannot use wavefunctions generated with >> pool >> >> parallelization unless wf_collect flag is set to 'true' for scf >> calc.s; >> >> also one has to use the same no. of proc.s as were used for scf >> calc.s >> >> to >> >> get projected DOS. >> >> >> >> Now my question is are these interpretations correct? Or they may >> change >> >> for some other system?? Do I need to do some more checks to ascertain >> >> these? If yes, what sort of tests? >> >> >> >> Thanks for reading this long mail patiently, but I need to clarify on >> >> these points before I can start with bigger systems. >> >> Sincerely, >> >> Madhura. >> >> >> >> >> >> >> > >> > -- >> > Andrea Ferretti >> > MIT, Dept Material Science & Engineering >> > bldg 13-4078, 77, Massachusetts Ave, Cambridge, MA >> > Tel: +1 617-452-2455; Skype: andrea_ferretti >> > URL: http://quasiamore.mit.edu >> > >> > Please, if possible, don't send me MS Word or PowerPoint attachments >> > Why? See: http://www.gnu.org/philosophy/no-word-attachments.html >> > >> > >> > _______________________________________________ >> > Pw_forum mailing list >> > Pw_forum at pwscf.org >> > http://www.democritos.it/mailman/listinfo/pw_forum >> > >> >> >> > > -- > Andrea Ferretti > MIT, Dept Material Science & Engineering > bldg 13-4078, 77, Massachusetts Ave, Cambridge, MA > Tel: +1 617-452-2455; Skype: andrea_ferretti > URL: http://quasiamore.mit.edu > > Please, if possible, don't send me MS Word or PowerPoint attachments > Why? See: http://www.gnu.org/philosophy/no-word-attachments.html > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Madhura Marathe, PhD student, TSU, JNCASR, Bangalore. India. Phone No: +91-80-22082835