[Users] highest output frequency for CarpetIOBasic?

[Roland Haas]

Hello Bernard,

> Something new (I think) and trivial, but is annoying me.
> 
> For diagnostic purposes, I was running a Cactus/Carpet executable (ETK Maxwell) with CarpetIOBasic::output_1Devery = 1. To my surprise, the output happens every *two* timesteps. When I switch the parameter to 2, the same thing happens. So I get the following behaviour:
> 
> parameter value  => actual output frequency
> -------------------------------------------------------------
> 1 => 2
> 2 => 2
> 4 => 4
> 8 => 8
> 
> The grid has multiple refinement levels. I tried a smaller testsuite (perhaps one of the ML_BSSN tests, which are unigrid), and there "output_1Devery = 1" really did produce output every timestep.
> 
> I know a proper report needs a sample parameter file for reproducibility, but before I get that (not logged into the right machine right now), perhaps someone could tell me why this -might- happen? The logic in the IOBasic thorn seems simple enough ...
The behaviour you describe occurs if you have
carpet::max_refinement_levels larger than the largest existing
refinement level (eg. in CarpetRegrid2?). cctk_iteration counts
iterations on the finest possible grid so if not all grid exists you get
the behaviour your describe since Carpet skips non-existing refinement
levels almost completely.

Yours,
Roland

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