On Fri, Jul 30, 2010, InSuk Joung wrote:
> if( uv == 0. ){ /* or maybe uv < 1.d-10 or something? */
> co = 1.0; /* or maybe something else?? */
> } else {
>
> Isn't this necessary above?
> den = 1.0
Yes. I didn't have the code in front of me, and didn't see that den is
used elsewhere.
>
> Otherwise, den is an arbitrary number. I am not sure whether it will cause
> a problem.
>
>
> Also, similar things are in sff2.c
>
> line 1265:
>
> assert(bi > 0.01);
> assert(bk > 0.01);
>
> Is this really necessary?
I think something is necessary if you really must have bond angles of 180
degrees. The diehedral angle (and hence its derivative) is undefined there.
Instead of triggering an assert, one could put in dummy values (as I suggested
in eff.c), on the assumption that everything will be multiplied by zero later
on anyway. But we might really want to think about having leap strip out
zero force constant diehedrals before the prmtop is written, so that this
problem never comes up....that would be a better solution, since otherwise
the sff code would have to double check that the force constant really is
zero.
....dac
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Received on Fri Jul 30 2010 - 19:00:03 PDT
