[Users] Norm2 calculation on different grid levels

[Haas, Roland]

Hello Elena,

if you schedule your function using:

options: level

instead of

options: global

then a call to Cactus' reduction interface will compute the reduction
only over the current refinement level.

Note that the sum of the norm2 of all the levels will not be the same
as the norm2 of all levels computed at once (because when computing
only on a single level Carpet will not "cut out" regions where a finer
grid exists).

The alternative is to introduce a helper grid function where you
manually zero out the regions you do not care about then compute the
norm of that grid function.

You can use Carpet's aliased function GetRefinementLevel to find out
the current refinement level:

CCTK_INT FUNCTION                         \
    GetRefinementLevels                   \
        (CCTK_POINTER_TO_CONST IN cctkGH)
PROVIDES FUNCTION GetRefinementLevels \
    WITH Carpet_GetRefinementLevels   \
    LANGUAGE C

You can copy (or use) GenericFD's GenericFD_GetBoundaryInfo function to
get information about whether a given face is a boundary and if so what
kind of boundary. 

See
repos/Kranc/Auxiliary/Cactus/KrancNumericalTools/GenericFD/src/GenericFD.c

Yours,
Roland

> Hello,
> I'm doing a simulation for BBH and I want to calculate the norm2 of the
> Hamiltonian constraints on different grid levels. Ideally i would like to
> calculate it first removing the first level of the grid, then removing it
> and the second one and so on...(the purpose is that i want to exclude the
> boundary contribution to the calculation). Do you know if there is a tool
> in the ET to do it?
> 
> Thanks
> 
> Elena De Paoli



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