[Users] ReflectionSymmetry, tensor tags, ML_BSSN, etc.

[John Baker]

Hi,
     We've run into some problems recently with our evolution
code, which boil done to the fact that we'd developed the
code to support the sort of reflection symmetry defined
in cartgrid3d, but recently started working with other thorns
which are expecting the use of ReflectionSymmetry to define
reflection symmetries.
      I assume that the motivation for this transition was to
support more general grids, multipatch codes, etc, but I
haven't found any documentation for the ReflectionSymmetry
thorn, or any explanation of its use.
     One likely problem we are having is that we haven't applied
any tensor-related tags in our interface.ccl, and rumor has it
around here that ReflectionSymmetry relies on these tags.
Presumably there are other EinsteinToolkit thorns which rely on
tensor tags as well.
     I did find one document giving some explanation of tensor
tags

http://cactuscode.org/documentation/CoreDoc.pdf

(thanks Erik).  Erik outlines a number of potential tags there, but
I would like to know which of these are required to support
interaction which the various thorns in the toolkit?

Looking at various other interface.ccl files, there didn't seem to be
a high degree of consistency about which tags are set.  Some
also naively appear to be set incorrectly, in ML_BSSN.  For instance:

CCTK_REAL ML_trace_curv type=GF timelevels=3 
tags='tensortypealias="Scalar" tensorweight=1.0000000000000000000'
{
   trK
} "ML_trace_curv"

Which seems to declare the trK to be a tensor density.  If this is 
indeed wrong,
and no one has noticed, then I infer that tensorweight may not really be 
used
by anything important.

If anyone can clarify these issues for me I would appreciate it.
Thanks,
John.