[gmx-users] Relaxation / precision

[David van der Spoel]

On Tue, 8 Jan 2002, Andrew Horsfield wrote:

>  Step 61, E-Pot = -2.0995914062e+05, F-max =  1.06133e+04
>  Step 62, E-Pot = -2.0994365625e+05, F-max =  1.57691e+05
>  Negative w:  -3.571208700467e+21
>  z=  -1.243719761920e+11
>  gpa=   2.476396229114e+11, gpb=   7.688429179760e+10
>  a=   0.000000000000e+00, b=   5.904069366017e-10
>  EpotA=  -2.099436562500e+05, EpotB=  -2.098553125000e+05
>  Negative number for sqrt encountered (-3571208700466867208192.000000)
>  Terminating minimization
>
>Is this a precision problem, or is it something else?
Yes.

>(I cannot get a double precision code to work with PME, which is why I
>have not tested this out.)
Why not?

Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++