[gmx-developers] no pull

[Berk Hess]

>2) In the umbrella sampling code in pull.c there is
>a subroutine do_umbrella containing a function put_dvec_in_box.
>This function is appearently meant to account for periodic
>boundary conditions when calculating the distance between
>the reference and the pull group. This function does not
>do what it was intended to do. I believe this is a bug.
>(umbrella sampling only gives reasonable results when
>  a) this funtion is commented out, and
>  b) (maybe ?) the pulled group does not cross a cell boundary.)

This looks like a bug.
To fix it replace:

/* Find vector between current and desired positions */
    dvec_sub(pull->grp[i].x_ref, pull->grp[i].x_unc, dr);

    put_dvec_in_box(box,dr);

with:

/* Find vector between current and desired positions */
    d_pbc_dx(box,pull->grp[i].x_ref, pull->grp[i].x_unc, dr);

I did not test it, so please report back if it works.

Berk.

_________________________________________________________________
Play online games with your friends with MSN Messenger 
http://messenger.msn.nl/