[gmx-developers] econq settings in constrain()

[Peter Matthews Kasson]

I'm in the midst of an ugly hack of the Gromacs code to calculate forces for an arbitrary set of coordinates.  I've been borrowing from the energy minimization code, but I'm running into a message in constr.c:

 if (econq == econqForce && !EI_ENERGY_MINIMIZATION(ir->eI))
   gmx_incons("constrain called for forces while not doing energy minimization, can not do this while the LINCS and SETTLE constraint connection matrices are mass weighted");

I'm assuming that's there for a good reason.  Does anyone have a sense for what the econq setting does and what I should set it to in this case?  The constraint code is just a touch hard to follow.  (I could  obviously kudge things so the inputrec looks like an energy minimization run, but I'd like to know what I'm doing first...)

Thanks!