[Wien] Possible bugs in Mixer

[Peter Blaha]

"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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