hi Ian,
>> for the purposes of trying a particular gauge condition, we'd like to have a
>> grid function (let's
>> call it "shift_t0") that's set to be equal to the shift at t=0. we don't
>> want this function to
>> evolve at all; we just want this grid function to be accessible at all times
>> (with exactly the same
>> values).
>>
>> is there something in particular that we need to watch out for, when doing
>> this? we ask because
>> we've noticed that when doing things in a "naive"* way, sometimes NaNs start
>> developing at some
>> point in the evolution (seemingly near refinement boundaries and when
>> regriding). we noticed that
>> exactly the same thing happens for the "puncture_u" grid function in
>> TwoPunctures: this function is
>> only used at t=0; however, if one activates storage for it and asks for its
>> output, at some point
>> NaNs start developing in the output, even though the function is never used
>> again. so, what would be
>> the standard way of defining a grid function that is constant in time?
>>
>> thanks,
>> Miguel & Helvi
>>
>> * by "naive", we mean essentially the following
>>
>> in schedule.ccl we have
>>
>> STORAGE: shift_t0[1]
>>
>> in interface.ccl we have
>>
>> CCTK_REAL shift_t0 type=gf timelevels=1 tags='tensortypealias="U"
>> tags='prolongation="none"'
>> {
>> betax_t0 betay_t0 betaz_t0
>> } "shift vector at t=0"
>>
>> and we set its value (on the whole grid) at a function call at CCTK_INITIAL
>> after ADMBase_PostInitial
>
> Does this happen only after regridding? By not prolongating the refinement
> boundaries, it's not
> clear how the "new" bits of the grid are supposed to be filled when the fine
> grids move. Could this
> be the problem? If you give the gridfunction 3 timelevels and remove
> "prolongation=none", do the
> NaNs go away?
it seems to happen only after regridding, yes. we did try precisely that (using
3 timelevels and
prolongating) but the NaNs still appeared...
thanks,
Miguel
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