[Pw_forum] Restarting PWSCF - usability issues

[Konstantin Kudin]

> restarting with atomic wfc usually implies that
> several iterations are needed 
> to diagonalize the hamiltonian because the threshold
> is more strict than the 
> one used for he first scf iteration of a
> "from_scratch" calculation.

> Moreover, since there is no way for the code to know
> at restart time whether 
> the starting potential is close to the scf one or
> not, the code doesn't know 
> the correct value for diagonalization threshold.

 Dear Carlo

 It appears that the code is already quite smart and
can detect such problems and lower the threshold on
the fly at the same cycle. So restarting from *.rho
file alone costs only that first diagonalization with
large threshold when it finds out that the threshold
should be smaller - hardly a big price to pay for the
convenience of not dealing with *.wfc* files.

 Here:
     The initial density is read from file     
yz_1s.rho
     Starting wfc are atomic
     total cpu time spent up to now is     34.38 secs
     iteration #  1     ecut=    28.00 ryd     beta=
.70
     Davidson diagonalization with overlap
     ethr =  1.00E-05,  avg # of iterations =  5.0
     Threshold (ethr) on eigenvalues was too large:
     Diagonalizing with lowered threshold
     Davidson diagonalization with overlap
     ethr =  2.29E-07,  avg # of iterations =  4.0

 Kostya


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