[gmx-users] pull forces

[Michael Brunsteiner]

Dear all,
does anybody know what the forces that are saved
in the f*xvg files from the pull-code actually are? are these:

1) the (sum of the) forces due to the normal non-bonded interactions
    in the system acting on the ref and the the full groups.
2) only the forces from the harmonic restraint.
3) the sum of both?

i just did a test writing out the forces from the trajectory
file, and looking at the relevant forces (the ones in the z-dimension
in my case, as i use pulldim N N Y and constrain the groups to stay
put in the x and y dimensions) it seems as if the forces on the
pull group are oscillating as expected, but the forces on the
reference group are close to, but not exactly(!) zero.
i am not sure how to interpret this ...

cheers
Michael