Does force dump include constraint forces with SHAKE/RATTLE?

[ejmeitz]

Good Morning,

I was curious if the forces that are dumped when you use SHAKE/RATTLE include the constraint forces? Looking at the source code there is this line which looks like it will be initialized to point to the global system forces (although I could not find that initialization). I know OpenMM does not include the constraint forces in their output but they also enact the constraints on the positions directly not through the forces like LAMMPS does.

I see this thread but I think that is a little different.

Thanks!

[akohlmey]

@ejmeitz

I was curious if the forces that are dumped when you use SHAKE/RATTLE include the constraint forces?

Yes.

The relevant line is this line

@ejmeitz

I could not find that initialization

The relevant lines for that are:

• for MD: https://github.com/lammps/lammps/blob/7ca2dcac62df9bd522e31615cc6a45c87f542bc5/src/RIGID/fix_shake.cpp#L539
• for minimization: https://github.com/lammps/lammps/blob/7ca2dcac62df9bd522e31615cc6a45c87f542bc5/src/RIGID/fix_shake.cpp#L729