[Carpet] weight is initialised differently with use_grid_structure_from_checkpoint feature turned on

[Thomas Radke]

Hi,

various people had reported the problem of norm output being slightly 
different after recovery compared with the values from the original 
checkpoint run. Bruno created the attached WaveToy parameter file which 
can be used to easily reproduce the problem.

I found that this happens only if 
IOHDF5::use_grid_structure_from_checkpoint is turned on, and buffer 
zones are being used. Disabling this feature does produce exactly the 
same values for all norms.

Luckily the problem doesn't seem to be in the recovery code or in the 
Carpet scheduler, affecting the entire evolution. In addition to the 
norms, I also compared the full phi function as 3D ASCII data and found 
it to be bitwise-identical. This indicates that the problem is related 
to the calculation of the norms only. Indeed, comparing the weight 
function in 3D ASCII does show differences in the buffer zones. Somehow 
the weight is initialised differently after recovery.

Is that enough information for you, Erik, to fix the problem ?

-- 
Cheers, Thomas.
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