Using 'cg' may sometimes work, but the machinery of iterative diagonalization is aimed towards finding the lowest M eigenvectors and eigenvalues when M << N = dimension of the basis set (number of plane waves). It's neither efficient nor numerically stable if M is a sizable fraction of N.
Paolo On Wed, Apr 5, 2017 at 6:43 PM, Kanak Datta <[email protected]> wrote: > Dear Thierry > > I faced the same Cholesky problem in my calculation. Although, I calculated > 2000 bands. The problem was gone when we used 'cg' diagonalization. I also > reduced the convergence threshold to 1d-8. Although, the simulation became > very slow, possibly due to 'cg' diagonalization. > > Thanks > Kanak > > _______________________________________ > Kanak Datta > Graduate Student > Electrical Engineering and Computer Science > University of Michigan, Ann Arbor > > On Wed, Apr 5, 2017 at 11:22 AM, Thierry Clette > <[email protected]> wrote: >> >> Hello, >> >> I want to do some nscf calculations in order to compute GW corrections >> afterwards. I know that I need a lot of bands to converge, around 3000 (I >> already did some convergence studies in another code). >> A example of an input is attached. >> This seems to be a problem for the code, as when I go higher than about >> 500 bands, I get the ¨error computing cholesky¨, which means the >> diagonalization fails. >> >> I read a lot of different topics in the mailing list reporting this >> problem, with various solutions such as : >> - parallelization on bands >> - CG diagonalization >> - bigger ¨diago_thr_init¨ (even if I need to be quite precise in the end) >> - beginning from a previous calculation with ~500 bands. >> >> I tried different things and it still didn't work. BTW, I know the >> calculation is possible, because I did it without problems in Abinit with >> the same parameters (Abinit seems to work differently). >> >> At this stage, I really don't know what I should do. Has someone already >> done successful calculations with so many bands ? >> >> Thanks in advance, >> >> Thierry Clette >> >> >> >> >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum > > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
