[Q-e-developers] Diagonalization method as input flag in ph.x

[Paolo Giannozzi]

On Fri, 2012-12-21 at 11:45 -0600, William Parker wrote:

> I modified my ph.x to compare it and Davidson on my test cases, 
> and a colleague of mine says that on a few systems he's had to 
> switch to conjugate gradient to get convergence.  Is there any 
> reason not to have it set as an input flag (default to 'david' 
> but optional 'cg') like in pw.x?

no special reason, apart that it's yet another option.
I would prefer that the reasons for occasional failures 
of the Davidson algorithm would be elucidated and removed, 
rather than resorting to a not-so-brilliant workaround 
(I wrote the CG routine: I have the right to criticise it), 
but I agree that no solution and a workaround is better 
than no solution and no workaround

Paolo
-- 
Paolo Giannozzi, IOM-Democritos and University of Udine, Italy