[Pw_forum] DOS and pDOS parallelization

[Madhura Marathe]

 Dear all,

 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.


-- 
Madhura Marathe,
PhD student, TSU,
JNCASR, Bangalore.
India.
Phone No: +91-80-22082835