[Pw_forum] new bfgs: strange behavior doing vc-relax

[Laurence Marks]

>From the look of this, and the file you sent it does not appear that
the curvature trap was activated so it must be something else (and I
do not know QE well enough to start guessing, so wont). As a double
check, according to the SVN (which I just checked out), in
Module/bfgs_mod.f90 the addition starts at line 738 and is

!       Now the trap itself
        if ( sdoty < 0.20D0*sBs ) then
!               Conventional damping
                Theta = 0.8D0*sBs/(sBs-sdoty)
                WRITE( stdout, '(/,5X,"WARNING: bfgs curvature condition ", &
                &     "failed, Theta=",F6.3)' )theta
                y = Theta*y + (1.D0 - Theta)*yH
        endif

If the write statement is not there, then the trap could not be
showing up, about a 1% chance.

Sorry to not be very helpful.

2011/4/18 Максим Попов <max.n.popov at gmail.com>:
> Dear Prof. Marks,
>
> I've sent the whole output file to your private e-mail as you suggested.
> Here I just put the result of grep command:
>
> CVS version:
> !    total energy              =    -242.65271405 Ry
>      number of bfgs steps    =   0
> !    total energy              =    -242.66331605 Ry
>      number of bfgs steps    =   1
> !    total energy              =    -242.66341971 Ry
>      number of bfgs steps    =   2
> !    total energy              =    -242.66342267 Ry
>      bfgs converged in   4 scf cycles and   3 bfgs steps
> !    total energy              =    -242.66284562 Ry
>
> v.4.2.1
> !    total energy              =    -242.65271405 Ry
>      number of bfgs steps    =   0
> !    total energy              =    -242.64460983 Ry
>      number of bfgs steps    =   1
> !    total energy              =    -242.66331847 Ry
>      number of bfgs steps    =   1
> !    total energy              =    -242.66341565 Ry
>      number of bfgs steps    =   2
> !    total energy              =    -242.66342170 Ry
>      number of bfgs steps    =   3
> !    total energy              =    -242.66342336 Ry
>      bfgs converged in   6 scf cycles and   4 bfgs steps
>
> Best regards,
> Maxim.
>
>
> 2011/4/18 Laurence Marks <L-marks at northwestern.edu>
>>
>> The latest BFGS has a curvature trap which can change the behavior
>> particularly if you have too few k-points. Can you please do
>>
>> grep -e "!    tot" -e bfgs WHATEVER.out
>>
>> (where WHATEVER is relevant) and send it to me, perhaps at my private
>> email (or the full .out file). I am not an expert with QE, but might
>> be able to say something.
>>
>> 2011/4/18 Максим Попов <max.n.popov at gmail.com>:
>> > Dear QE developers,
>> >
>> > comparing vc-relax calculations between BFGS(4.2.1) and the latest
>> > BFGS(from
>> > CVS) I faced  with a following problem:
>> > the newest QE calculates one extra point after achieving convergence
>> > criteria (etot_conv_thr,force_conv_thr,press_conv_thr),
>> > which leads to slightly higher total energy.
>> >
>> > Here are the two latest energies from outputs:
>> >        v.4.2.1                       CVS(18.04.2011)
>> >
>> > -242.66342170 Ry       -242.66342267 Ry
>> > -242.66342336 Ry       -242.66284562 Ry
>> >
>> > One can see that there is a good agreement between the last energy by
>> > v.4.2.1 and next to the last by CVS-version, whereas
>> > the last energy by CVS is higher by ~ 0.5 mRy.
>> >
>> > I tried relax (cell shape fixed) also - it works fine, no extra point
>> > calculation.
>> >
>> > --
>> > Best regards, Max Popov
>> > Ph.D. student
>> > Materials center Leoben (MCL), Leoben, Austria.
>> >
>> > _______________________________________________
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>> >
>> >
>>
>>
>>
>> --
>> Laurence Marks
>> Department of Materials Science and Engineering
>> MSE Rm 2036 Cook Hall
>> 2220 N Campus Drive
>> Northwestern University
>> Evanston, IL 60208, USA
>> Tel: (847) 491-3996 Fax: (847) 491-7820
>> email: L-marks at northwestern dot edu
>> Web: www.numis.northwestern.edu
>> Chair, Commission on Electron Crystallography of IUCR
>> www.numis.northwestern.edu/
>> Research is to see what everybody else has seen, and to think what
>> nobody else has thought
>> Albert Szent-Gyorgi
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>
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>



-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Research is to see what everybody else has seen, and to think what
nobody else has thought
Albert Szent-Gyorgi