[Users] Problem regriding using trigger thorn

[Roland Haas]

Hello Dhruv,

At runtime you have to steer the grid scalars in CarpetRegrid2 rather
than the parameters.

See the gallery example for hmns:
http://einsteintoolkit.org/gallery/bns/nsnstohmns.par

Trigger::Trigger_Checked_Variable[2]="SphericalSurface::sf_valid[2]"
Trigger::Trigger_Reduction       [2]=""
Trigger::Trigger_Relation        [2]=">"
Trigger::Trigger_Checked_Value   [2]=0.
Trigger::Trigger_Reaction        [2]="steerscalar"
Trigger::Trigger_Steered_Scalar      [2] = "CarpetRegrid2::num_levels[0]" # == num_levels_1
Trigger::Trigger_Steered_Scalar_Value[2] = "1"

and for the radii you can look up the Regrid2 docs 

http://einsteintoolkit.org/thornguide/Carpet/CarpetRegrid2/documentation.html

Trigger::Trigger_Steered_Scalar[triggernum] =
"carpetregrid2::radii[center]"

from its interface.ccl (center = 0 in your case for radius_1).

You also must set Trigger::Trigger_Steered_Scalar_Index[triggernum] to
the level needed (6 in your case).

Yours,
Roland

> Hello,
> I am running a simulation with Daniel Siegel where we use a base level
> plus 6 refinement levels, like the following:
> CarpetRegrid2::radius_1[1]  = 336.0    # dx/64
> CarpetRegrid2::radius_1[2]  = 168.0    # dx/64
> CarpetRegrid2::radius_1[3]  = 84.0    # dx/64
> CarpetRegrid2::radius_1[4]  = 42.0    # dx/64
> CarpetRegrid2::radius_1[5]  = 21.0    # dx/64
> CarpetRegrid2::radius_1[6]  = 10.5    # dx/64
> 
> We ran simulations of a neutrino-driven wind from a Neutron star, out
> to ~150 ms, and now we want to turn on a high magnetic field. We have
> tried B-fields of varying strengths, but if we try a B-field strength
> that is too high, we find errors generated on the innermost refinement
> level boundary. We believe if we enlarge the innermost box size ie.
> CarpetRegrid2::radius_1[6]  = 10.5 --> ~19-20, these errors would
> disappear. But we are having trouble doing this. In our attempt, we
> activate the trigger thorn with the following settings:
> 
> ActiveThorns = "Trigger"
> Trigger::Trigger_Debug = 1
> Trigger::Trigger_Once[0]=1
> Trigger::Trigger_Number =1
> Trigger::Trigger_Checked_Variable[0]="GRHydro::GRHydro_rho_min"
> Trigger::Trigger_Reduction       [0]=""
> Trigger::Trigger_Relation        [0]="<"
> Trigger::Trigger_Checked_Value   [0]= 1.1
> Trigger::Trigger_Reaction        [0]="steerparam"
> Trigger::Trigger_Steered_Parameter_Value [0] = "19.32"
> Trigger::Trigger_Steered_Parameter_Name  [0] = "radius_1[6]"
> Trigger::Trigger_Steered_Parameter_Thorn [0] = "CarpetRegrid2"
> 
> (We use a trivially satisfied trigger condition so that the parameter
> value is reset immediately upon restart.)
> Since the CarpetRegrid2 variable "radius_1[6]" is not steerable, we
> had to modify this to make it such. After turning debug on, we see the
> following output:
> 
> INFO (Trigger): Testing triggers
> INFO (Trigger): last_checked: -1
> INFO (Trigger): trigger nr. 0 fulfilled for GRHydro_rho_min
> (0.000000<1.100000)
> INFO (Trigger): Steering parameter
> INFO (Trigger): Parameter steered
> 
> Which supposedly successfully resets the value correctly. We believe
> that even though this may be the case, the actual grid is not
> changing. We plot the first 2 boundary levels and show them in the
> attached file.
> 
> There must be interpolation of the second innermost grid onto the
> innermost grid, and we believe this is not actually handled
> mid-simulation and thus doesn't not result in the change we expect.
> 
> Is there any simple way of changing the inner grid easily?
> Any help is much appreciated!
> 
> [image: image(1).png]
> 
> 
> Thanks,
> Dhruv Desai



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