[gmx-developers] parsing dihedraltypes 1 and 9

Zachmann, Martin m.zachmann at tum.de
Mon Feb 20 23:51:03 CET 2017

Hello all!

my question is about the specific way grompp handles the dihedraltypes 1 and 9. I realized that internally

both types are saved together in the same list (which is bt[ftype] in the push_dihedraltype() function), while all

other types are pushed in separate lists.

This leads to dihedrals with types 1 or 9 being matched to dihedraltypes (if they are assigned default values)

with any of 9 or 1 types, independent of their actual function-type. It could also lead to a dihedraltype with type 9

being added as multiple dihedral to a directly preceding dihedraltype with type 1 (if they have matching bondtypes).

I guess mixing types 1 and 9 is discouraged and there does not seem to be a standard gmx ff-file that would do this.

However, since matching of all other types is exlusive for those types, I do not understand why this approach was chosen.

It is legal to mix all other types in random order in the dihedraltypes section as well.

Why is there no individual enum for 9 in the types/idef.h as is the case with all other types 1,2,3,4,5,8?

Any help is greatly appreciated,

regards Martin

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