[Pw_forum] converged to wrong magnetic state of hcp cobalt in Opteron

wlyim at puccini.che.pitt.edu wlyim at puccini.che.pitt.edu
Fri Apr 14 09:23:11 CEST 2006 

Hi all,

I don't think different machine will generate very different initial 
wavefunction. For platinum, the energy in the first iteration step are the 
same from Origin and Opteron. As stated in my second post, the energies 
are different for cobalt. I think the "global minimum" issue cannot 
explain all these evidences. I wanna know any fundamental difference 
between Origin and Opteron (compiler, fft and math librarys) would cause 
this. One can get the input in my first post to test it on Opteron. I will 
be appreciated if anyone can tell what I did wrongly.

Many thanks in advance.

Best regards,
William

On Thu, 13 Apr 2006, Konstantin Kudin wrote:

>  Hi all,
> 
>  I'd like to point out that as long as the code converges to a proper
> *local* minimum, all is OK. One cannot really expect that the code is
> going to find the *global* minimum in a system where there are many
> accessible low energy minima. The way things are implemented is to find
> *a* minimum, not *the* minimum! Note that finding *the* minimum is a
> quite tricky issue, and not a solved one.
> 
>  Different platforms (compilers/architectures) might have different
> initial random wavefunctions, leading to different local minima. Is
> that a sign of a problem? - Not at all!
> 
>  Until things improve, making sure that the electronic state obtained
> is lowest in energy (i.e. the global minimum) is the operator's
> responsibility.
> 
>  Kostya
> 
> 
> --- wlyim at puccini.che.pitt.edu wrote:
> 
> > Dear Axel,
> > 
> > Thanks for your advice.
> > 
> > I have compiled pwscf.2.1.4 using EM64T Version 9.0 with MKL 8.0.1.
> > Again, 
> > the electronic structure went to the wrong state.
> > ==================================================
> > INTEL EM64T result:
> > !    total energy              =  -148.81668356 ryd
> >      estimated scf accuracy    <        2.0E-12 ryd
> > 
> >      band energy sum           =    15.05020564 ryd
> >      one-electron contribution =     6.02718174 ryd
> >      hartree contribution      =    21.83280277 ryd
> >      xc contribution           =   -65.85608487 ryd
> >      ewald contribution        =  -110.85073891 ryd
> >      correction for metals     =     0.03015572 ryd
> > 
> >      total magnetization       =     3.75 Bohr mag/cell
> >      absolute magnetization    =     4.14 Bohr mag/cell
> > =======================================================
> > 
> > It seemed to me that in this chemical system, the energy is
> > constantly
> > shifted by 0.06 Ry when compared to Origin result. I pick up the
> > first 
> > iteration step for comparison:
> > ================================================
> > Origin:
> >      iteration #  1     ecut=    30.00 ryd     beta=0.70
> >      Davidson diagonalization (with overlap)
> >      ethr =  1.00E-02,  avg # of iterations =  4.2
> > 
> >      npt with rhoup < 0:        2, npt tot    20736,      0.01 %
> > 
> >      npt with rhoup < 0:        2, npt tot    20736,      0.01 %
> > 
> >      total cpu time spent up to now is     15.75 secs
> > 
> >      total energy              =  -147.96340174 ryd
> >      estimated scf accuracy    <     2.11694003 ryd
> > 
> >      total magnetization       =     5.92 Bohr mag/cell
> >      absolute magnetization    =     5.97 Bohr mag/cell
> > =================================================
> > Opteron(PGI) or INTEL(EM64T) result:
> >      iteration #  1     ecut=    30.00 ryd     beta=0.70
> >      Davidson diagonalization (with overlap)
> >      ethr =  1.00E-02,  avg # of iterations =  4.1
> > 
> >      npt with rhoup < 0:        2, npt tot    20736,      0.01 %
> > 
> >      npt with rhoup < 0:        2, npt tot    20736,      0.01 %
> > 
> >      total cpu time spent up to now is     30.39 secs
> > 
> >      total energy              =  -147.90474844 ryd
> >      estimated scf accuracy    <     2.13792299 ryd
> > 
> >      total magnetization       =     5.95 Bohr mag/cell
> >      absolute magnetization    =     6.00 Bohr mag/cell
> > ======================================================
> > 
> > At the initial stage, I would expect that the "total energy" are
> > quite 
> > similar calculated in two different platforms. However this is not
> > the 
> > case. Origin's energy is about 0.06 Ry lower than that in Opteron.
> > And 
> > such a difference was kept till the end. I can't imagine what
> > reasoned for 
> > this. On the other hand, platinum is free of this problem.
> > 
> > Is it due to different fft treatments in Origin and Linux machines?
> > Or 
> > code/library problem?
> > 
> > Many thanks in advance.
> > 
> > Best regards,
> > William
> > 
> > On Thu, 13 Apr 2006, Axel Kohlmeyer wrote:
> > 
> > > On Thu, 13 Apr 2006 wlyim at puccini.che.pitt.edu wrote:
> > > 
> > > WL> Dear all,
> > > 
> > > dear william,
> > > 
> > > please check the mailing list archives. the PGI compilers version
> > 5.x
> > > are _known_ to miscompile several parts of quantum espresso (and
> > not
> > > only that code, i know of several other DFT codes as well).
> > > the same is true for quite few SGI compilers...
> > > if you can, please try with the intel (EM64t) compilers on opteron
> > > to check, whether it is still going to the wrong state. it
> > additionally
> > > may depend on the kind of BLAS/LAPACK library you are using. there
> > are 
> > > a few bugs in several of them as well.
> > > 
> > > best regards,
> > >   axel.
> > > 
> > > WL> 
> > > WL> I did a test on crystalline hcp cobalt by pwscf.2.1.4, both on
> > Opteron
> > > WL> (pgf90 5.2-4, lam 7.1.1) and Origin. I found that the
> > calculation 
> > > WL> converged to a wrong magnetic state in Opteron, while the
> > calculation in 
> > > WL> Origin was okay.
> > > 
> > > [...]
> > > 
> > > WL> I used the PBE uspp as provided in pwscf website. On the other
> > hand, I 
> > > WL> have also tried the calculations on platinum, which is a
> > closed-shell 
> > > WL> system, and I got essentially the same results from Opteron and
> > Origin.
> > > WL> 
> > > WL> Does anyone experience a similar thing? I will be appreciated
> > if someone 
> > > WL> can give a help hand.
> > > WL> 
> > > WL> Many thanks in advance!
> > > WL> 
> > > WL> I am also attaching the input file at the bottom of this
> > meesage.
> > > WL> 
> > > WL> regards,
> > > WL> William
> > > WL> 
> > > 
> > > [...]
> > > 
> > > 
> > 
> > 
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> > 
> 
> 
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