[Wien] Possible bugs in Mixer

[Laurence Marks]

Sorry Peter, this is not working on the DFT eigenvectors and convergence is
not relevant. It is doing a SVD of {YY+lamdba*SY}} to generate a
Penrose-Moore pseudoinverse. The vectors of an SVD are not unique within a
phase term.

On Fri, Dec 19, 2025 at 12:41 PM Peter Blaha <peter.blaha at tuwien.ac.at>
wrote:

> "different results":
> I'd expect it is either not fully self-consistent for the
> quantity/accuracy of interest (do on both computers 100 more
> iterations), or different hardware (AVXxx, different cpu, cache, ...),
> software like mkl-, ifort- versions or compiler options or ...
>
>
>
> Am 19.12.2025 um 17:35 schrieb Guoping Zhang:
> > Dear Profs. Blaha and Marks and wien users,
> >
> > I have a question on how the new Mixer is implemented as it gives me
> > different results on different computers.  Different results mean that
> > the eigenvalues differ by 10^-6 ry, so the wavefunctions are even
> > worse. I am using wien2k_13 version, but there is no difference for
> > newer versions.
> >
> >
> > In FprojmemR1m.F, call DGESVD gets SVD of Vect, but SVD normally
> > produces an arbitrary sign for U and VT for the same Vect like
> > vect    1     1     1.7542057564
> > vect    1     2     1.7522638412
> > vect    2     1     1.7441856025
> > vect    2     2     1.7425017533
> >
> > In one case, my U is
> >
> >
> > debug3c.outputm:MMT91 U VT    1     1    -0.7091042206   -0.7074733729
> > debug3c.outputm:MMT91 U VT    1     2    -0.7051036834   -0.7067399994
> > debug3c.outputm:MMT91 U VT    2     1    -0.7051036834   -0.7067399994
> > debug3c.outputm:MMT91 U VT    2     2     0.7091042206    0.7074733729
> >
> > Another case has
> >
> > debug11.outputm:MMT91 U VT    1     1     0.7091042206    0.7074733728
> > debug11.outputm:MMT91 U VT    1     2    -0.7051036834    0.7067399994
> > debug11.outputm:MMT91 U VT    2     1     0.7051036834   -0.7067399994
> > debug11.outputm:MMT91 U VT    2     2     0.7091042206    0.7074733728
> >
> > I run 4 iterations to activate the mixer.  When I diff case.scf, these
> two
> > cases have no difference to the last digit,
> >
> > But after the mixing, it differs a lot though the total energy is the
> > same (which is not my interest).
> >
> > My questions are (1) whether the new mixer finally uses some products
> > like (U x VT) to generate the new charge density, and (2) whether you
> > have examples that I use to verify this arbitrary sign does not matter.
> >
> > Thank you so much in advance!
> >
> > Best wishes,
> >
> > Guoping
> >
> >
> > _______________________________________________
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>
> --
> -----------------------------------------------------------------------
> Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Email: peter.blaha at tuwien.ac.at
> WWW:   http://www.imc.tuwien.ac.at      WIEN2k: http://www.wien2k.at
> -------------------------------------------------------------------------
>
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-- 
Emeritus Professor Laurence Marks (Laurie)
Northwestern University
Webpage <http://www.numis.northwestern.edu> and Google Scholar link
<http://scholar.google.com/citations?user=zmHhI9gAAAAJ&hl=en>
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Györgyi
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