[QE-developers] Bug in non self-consistent calculation

[Davide Ceresoli]

Dear Lorenzo,
     is your QE compiled with a decent compiler and with decent libraries?
Your inputs works perfectly for me, with no crashes.

HTH.
D.



On 6/12/19 12:29 PM, Lorenzo Monacelli wrote:
> Dear QE developers,
> 
> I think I found a bad bug in the non self-consistent calculation of pw.x
> 
> While the self consistent calculation ends properly, when running a non 
> self-consistent calculation results in a crash with the error:
> 
>   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>       task #         0
>       from cdiaghg : error #        40
>       S matrix not positive definite
>   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> I checked the cdiaghg subroutine, the S matrix should be the overlap matrix for 
> the eigenvalue problem Hv = eSv
> 
> That, in case of local Norm Conserving pseudo of Hydrogen (my calculation)  I 
> suppose it should be the identity, however, if I enforce it to be the indentity 
> at the beginning of cdiaghg the code says that it is not able to converge the 
> scf caclulation either.
> 
> I attach the input of the scf calculation (that converges) and the one of the 
> non-self-consistent calculation (that produces this output).
> 
> I also tried to switch the diagonalization method to cg as suggested as fix, but 
> nothing changes.
> 
> I modified also the cdiaghg subroutine, to print the S matrix, that you find 
> attached (random numbers, seems to be uninitialized).
> 
> In both the diagonalization methods if I enforce S to be the identity matrix the 
> code crashes by saying that it was not able to converge.
> 
> The problem seems to arise especially if I request for more bands with the nbnd 
> flag in system (but sometimes it occurs even if no extra band is required).
> 
> The QE version I used is the current version in the develop branch of gitlab, 
> but I noticed the same error occurring also with 6.3 and 6.2 in other cases.
> 
> If I ask for exactly the same input file a scf calculation (instead of a nscf) 
> everything goes fine (same K points, same diagonalization, same number of 
> extrabands), but indeed, this is not what I would like to do...
> 
> I I run the nscf calculation after a scf calculation with exactly the same input 
> (that works), the nscf calculation fails (this means that the crash is not 
> caused by a bad starting point for the density).
> 
> All these make me really think of a bug in the nscf calculation, rather than a 
> wrong input.
> 
> Best regards,
> 
> Lorenzo Monacelli
> 
> 
> P.S.
> 
> In the attached file the pw_* are the nscf input and output, the scf* are the 
> scf input and output. I run
> 
> 
> 
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-- 
+--------------------------------------------------------------+
   Davide Ceresoli
   CNR Institute of Molecular Science and Technology (CNR-ISTM)
   c/o University of Milan, via Golgi 19, 20133 Milan, Italy
   Email: davide.ceresoli at cnr.it
   Phone: +39-02-50314276, +39-347-1001570 (mobile)
   Skype: dceresoli
   Website: http://sites.google.com/site/dceresoli/
+--------------------------------------------------------------+