[lammps-users] Increasing maximum number of group elements to thousands (from current 32)

Dear users,
I have a problem where in principle I need to define thousands of groups but the maximum number of groups in LAMMPS is 32. More specifically,
the problem consists of defining for every side-chain/residue of a polymer and a corresponding fictitious atom, a harmonic restraint between the center of mass of the side chain, and the corresponding fictitious atom.
The number of such sidechains will ultimately be a few thousand.

Were they just a handful, this could trivially be done using the spring fix.

Is there any point in struggling to increase the maximum number of groups from 32 to this enormous value, or would it be better to modify some other fix function to achieve the same effect ?
By the way, the number of atoms in each side chains is always 20, and they are all relatively heavy (the lightest atom therein being carbon).

Thanks in advance for your comments/suggestions.

Best Regards,
Donal
Dr. Donal MacKernan
UCD School of Physics, Dublin.

Is there any point in struggling to increase the maximum number of groups from 32 to this enormous value, or would it >be better to modify some other fix function to achieve the same effect ?

You can't do this in any simple way. You're better off not using
groups, but molecule ID or some
other means to constrain what you want.

Steve