[Fwd: Re: [gmx-users] Steepest Descents did not converge]

[Christoph Freudenberger]

Dear Derrick,

please post the dicussion to the list.

-------- Original Message --------
 >Subject: Re: [gmx-users] Steepest Descents did not converge
 >Date: Thu, 10 Jul 2003 14:48:34 -0230 (NDT)
 >From: Derrick Guang Yuh Lee <k24dgyl at morgan.ucs.mun.ca>
 >To: Christoph Freudenberger <christoph.freudenberger at chemie.uni-ulm.de>
 >
 >dear christoph
 >
 >thank you for you info, i will try that. a quick question though, what is,
 >if you know, the direct results of the steepest decent not converging?

Not quite clear what you accually mean...

 >how does this effect my data? again, thank you for your help.
Not at all. You have not yet even started ro equilibrate
your system. your not going to include the minimization results in
the analysis, are you?

 > - derrick



 > derrick Lee
 > faculty of Science
 > Memorial University of Newfoundland
 > k24dgyl at mun.ca or derrickglee at hotmail.com

 >"a teacher is never a giver of truth - he is a guide, a pointer to the
 >truth that each student must find for himself. a good teacher is merely a
 >catalyst."
 >                                                             - bruce lee

On Thu, 10 Jul 2003, Christoph Freudenberger wrote:

 >
 >
 > Derrick Guang Yuh Lee wrote:
 > > dear gmx-users
 > >
 > > right now i am running the mdrun program in gromacs on a dppc lipid
 > > bilayer (downloaded from the tieleman's website), and i keep on getting
 > > this error:
 > >
 > > ---------------------------------------------------------------------------
 > > Steepest Descents:
 > >    Tolerance         =  1.00000e+02
 > >    Number of steps   =      1000000
 > > Step=  0, Dmax= 1.0e-02 nm, Epot= -2.99255e+05 Fmax= 5.37264e+03, atom=3275
 > > Step=  1, Dmax= 1.0e-02 nm, Epot= -3.02471e+05 Fmax= 2.40785e+03, atom=3024
 > > Step=  4, Dmax= 3.0e-03 nm, Epot= -3.02866e+05 Fmax= 1.90722e+03, atom=13315
 > > Step= 16, Dmax= 1.8e-06 nm, Epot= -3.02866e+05 Fmax= 2.63245e+03, atom=16161
 > >
 > > Stepsize too small (8.78906e-07 nm)Converged to machine precision,
 > > but not to the requested precision (100)
 > > You might need to increase your constraint accuracy, or turn
 > > off constraints alltogether (set constraints = none in mdp file)
 > >
 > > writing lowest energy coordinates.
 > >
 > > Steepest Descents did not converge in 17 steps
 > >   Potential Energy  = -3.02866e+05
 > > Maximum force:  1.90722e+03
 > > ---------------------------------------------------------------------------
 >
 > This is not an error, steepest decent has just reached it's limit.
 > If you want to start an MD for the system just
 > proceed to a short run in NVT with a rather short time step (1fs or
 > maybe even less). If the system runs fine you can turn on pressure
 > coupling (if you want to) and increase the time step.
 >
 > If you want to do further minimization switch over to cg.
 >
 > regards
 > --
 > Christoph Freudenberger
 > Abt. Organische Chemie I AK Siehl - Uni Ulm -Tel: ++49-731-502-2785
 >
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 >


-- 
Christoph Freudenberger
Abt. Organische Chemie I AK Siehl - Uni Ulm -Tel: ++49-731-502-2785