CHARMM cp=0 dihedrals are not ignored
I noticed that the CHARMM FF has dihedrals defined with the force constant cp=0. And they don't seem to be automatically removed.
Erik added the comment to assign_parm (conparm.c): * Second, if the force constant is zero in both A and B states, we set the phase * and multiplicity to zero too so the interaction gets removed during clean-up.
But I cannot find any code which does this clean-up (neither in grompp nor mdrun) and I also just tested that the cpA(=cpB)=0 functype is in the tpr file.
Am I missing something or are the cp=0 dihedrals not removed? If so where should they be removed?
Add check to remove zero Charmm dihedrals
Proper torsions where the force constant is zero
in both A and B states are now removed. We also
check for other angle, torsion, and restraint
functional types, and if all parameters are zero
for these the interaction is not added. This will
not change any results, but increase performance
slightly by not calculating unnecessary interactions.
#1 Updated by Erik Lindahl over 9 years ago
- Priority changed from Normal to Low
- Target version changed from 4.5.5 to 5.0
The removal used to be done while converting parameters.
However, I would classify this as a hard bug since it doesn't affect the quality of any results (actually, it won't affect results at all, but we end up computing a couple of zero interactions). We should look into it some time, but there's no reason to hold 4.5.5 for this.