Runtime Parameters¶

This page briefly describes parameters that may be defined in the input file. All parameters are case sensitive. Required parameters for all setups are listed first, followed by parameters required for specific Makefile flags or initial conditions. A sample parameter file can be found in the examples directory.

Todo

Port me from the wiki

Required Parameters¶

These parameters are required for all simulations

Parameter:: nx
Summary:: number of grid cells along the x dimension
Type:: int
Default:: None

Parameter:: ny
Summary:: number of grid cells along the y dimension
Type:: int
Default:: None

In a 1D problem, this must be set to 1

Parameter:: nz
Summary:: number of grid cells along the z dimension
Type:: int
Default:: None

In 1D and 2D problems, this must be set to 1

Parameter:: xmin
Summary:: x direction lower boundary (in code units)
Type:: float
Default:: None

Parameter:: ymin
Summary:: y direction lower boundary (in code units)
Type:: float
Default:: None

Parameter:: zmin
Summary:: z direction lower boundary (in code units)
Type:: float
Default:: None

Todo

Port over the remaining parameters

Cosmology¶

The parameters required when compiled with COSMOLOGY are H0, Omega_M, Omega_L, and Omega_b.

Parameter:: H0
Summary:: Present-day Hubble Rate in units of km/s/Mpc
Type:: float
Default:: None

Parameter:: Omega_M
Summary:: Present-day matter energy-density
Type:: float
Default:: None

Parameter:: Omega_L
Summary:: Present-day dark energy energy-density
Type:: float
Default:: None

Parameter:: Omega_b
Summary:: Present-day baryonic matter energy-density
Type:: float
Default:: None

Parameter:: Omega_R
Summary:: Present-day radiation energy-density
Type:: float
Default:: 0.0

Parameter:: w0
Summary:: Present-day dark energy equation of state. The \(w_0\) in a \(w(a) = w_0 + w_a (1-a)\) dark energy equation of state parameterization.
Type:: float
Default:: -1.0

Parameter:: wa
Summary:: Linear interpolation of dark energy equation of state to early Universe. The \(w_a\) in a \(w(a) = w_0 + w_a (1-a)\) dark energy equation of state parameterization.
Type:: float
Default:: 0.0

Parameter:: scale_outputs_file
Summary:: Path to data file describing the scale factor values to output snapshots.
Type:: str
Default:: None

We expect increasing scale factor values in this file

Parameter:: wDE_file
Summary:: Path to data file describing a redshift-dependent dark energy equation of state
Type:: str
Default:: None

We expect increasing redshift values in this file. Each row must have a z wDE(z) value with a space delimiter. Table must have an entry at redshift \(z=0\). Table should look like

# output the first five lines of wDE_file
$ head wDE_file -n 5
# z, w
0.000000000000000000e+00 -9.767616499273475972e-01
6.938631476027579126e-03 -9.769941793369097960e-01
1.392540755881421788e-02 -9.772263520514015145e-01
2.096066230604587410e-02 -9.774581369813842846e-01

When specified, overrides w0 and wa.

Todo

include Init_redshift

Chemistry¶

These parameters should all be specified in the [chemistry] parameter table.

Parameter:: chemistry.kind
Summary:: kind of chemistry solver to use
Type:: str
Default:: “none” (unless the CHEMISTRY_GPU or COOLING_GRACKLE macro is defined)

This parameter specifies the choice of chemistry cooling solver. When CHEMISTRY_GPU and COOLING_GRACKLE are not defined, this defaults to “none.”

Important

At the time of writing, if you want to use “chemistry-gpu,” you MUST use the CHEMISTRY_GPU Makefile parameter. Likewise, if you want to use “grackle”, you MUST use the COOLING_GRACKLE Makefile parameter. In both cases, we do not allow the choices to be overwritten. For user convenience, the default value are set to these options when the Makefile parameter is detected.

Name	Meaning
“none”	No chemistry or cooling
“tabulated-cloudy”	path to data file used by “tabulated-cooling” solver
“piecewise-cie”	piecewise-parabolic fit to a collisional ionization equilibrium (CIE)
“piecewise-ti+cie”	Analytic cooling/heating recipe that roughly matches the “TI” cooling runs shown in in Kim & Ostriker 2015
“chemistry-gpu”	Non-equilibrium Hydrogen/Helium chemical network with heating/cooling (only usable when the `CHEMISTRY_GPU` macro is defined)
“grackle”	CPU-based non-equilibrium primordial chemistry with heating/cooling (only usable when the `COOLING_GRACKLE` macro is defined)

Parameter:: chemistry.data_file
Summary:: path to data file used by “tabulated-cloudy” solver
Type:: str
Default:: None

It is an error to specify this parameter when chemistry.kind chemistry cooling solver other than “tabulated-cloudy.”

Parameter:: chemistry.photoelectric_heating
Summary:: enables photoelectric-heating
Type:: bool
Default:: false

Can be used to enable photoelectric-heating when chemistry.kind is set to “tabulated-cloudy” or “piecewise-ti+cie”. It is an error to specify this for any other cooling.kind.

Parameter:: chemistry.photoelectric_n_av_cgs
Summary:: Parameterizes photoelectric heating
Type:: float
Default:: 100.0

When chemistry.photoelectric_heating is true, this parameter can be used to specify the average number-density in the domain in cgs units (which is used to compute impact of photoelectric heating).

It is an error to specify this parameter when chemistry.photoelectric_heating is false.

Feedback¶

These parameters should all be specified in the [feedback] parameter table.

Parameter:: feedback.boundary_strategy
Summary:: Specify handling in the scenario when a feedback event is scheduled to occur for a particle near the edge of the grid-block that contains the particle and the stencil overlap with cells outside of the grid-block (this includes ghost cells).
Type:: str
Default:: None: must be provided

Valid options include:

"ignore_issues": as its name implies, this choice ignores the issue (essentially we lose some fraction of the injected “stuff”).
"snap": compute the stencils as if the source-particle positions were snapped to the closest position in the grid-block such that the stencil only includes cells within a block.

In the future, a more robust strategy will involve MPI communication (and/or ghost particles)

Parameter:: feedback.snr_filename
Summary:: path to the table used to determine the supernova rate (for the "table" rates)
Type:: str
Default:: None

This parameter is meaningless if feedback.sn_rate isn’t set to "table".

If this parameter is not set, then a default constant SNR is used. The default SNR corresponds to 1 supernova per \(100 M_\odot\) of cluster mass, spread out over 36 Myr, starting when the cluster is 4 Myr old. A sample Starburst99 file is included in the source code at src/particles/starburst99_snr.txt. The sample represents a \(10^6 M_\odot\) fixed mass cluster, created using a Kroupa initial mass function, and with an \(8 \mathrm{M}_\odot\) supernova cutoff. More details are provided here.

Parameter:: feedback.sn_model
Summary:: Specifies the name of the supernova model
Type:: str
Default:: None

More details are provided here.

Parameter:: feedback.sn_rate
Summary:: Specifies the kind of supernova rate
Type:: str
Default:: "table"

When "table" (the default value) is specified, Cholla determines the rate from a table. "immediate_sn" schedules a single supernova to occur, immediately after the simulation starts. More details are provided here.

Gravity¶

These parameters should all be specified in the [gravity] parameter table.

Parameter:: gravity.gas_only_use_static_grav
Summary:: Specify whether the gas is only sensitive to the analytic potential or to the analytic potential and self-gravity.
Type:: bool
Default:: false