Pull group 0 shows up in logs, states one more group than actually exists - Redmine #2143

Archive from user: James Barnett

In md.log when using the pull code, there is always a “pull-group 0” output with no atoms. grompp does not accept “pull-group0-name”, etc, so the count should start at 1. Additionally, pull-ngroups always is set to one number higher than the actual number of pull groups set. For example, setting “pull-ngroups” to 2 in the mdp file results in the md.log stating that “pull-ngroups” is 3; the processed mdp file has the correct number. Additionally later in the log it states (using to virtual sites in this one, so no masses):

Will apply potential COM pulling
with 1 pull coordinate and 3 groups
Pull group 1:     1 atoms, mass     0.000
Pull group 2:     1 atoms, mass     0.000

(from redmine: issue id 2143, created on 2017-03-20 by gmxdefault, closed on 2018-01-02)

• Changesets:
  • Revision fba92a59 by Erik Lindahl on 2018-01-02T11:12:37Z:

Don't write reference pull group 0 to log

This is an internal group used for absolute
references, which cannot be set by users, so
printing it just leads to confusion.

Fixes #2143.

Change-Id: I89ee3a0e3a65855735b745f4ed7615ca47bfd36a

• Revision 3891bbbb by Berk Hess on 2018-04-03T07:21:27Z:

Do not calculate COM for pull group 0

Pull group 0 is an absolute reference with coordinates 0,0,0,
so it is clearer to never compute its center of mass.

Refs #2143

Change-Id: Ifa974ab84afe303594c3b65e9567e0568bb151a9