Input File 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 optional parameters required for specific Makefile flags or initial conditions. A sample parameter file can be found in the examples directory.

Required Parameters

For 1D problems, ny and nz should be set to 1. For 2D problems, nz should be set to 1.

nx: number of grid cells in the x dimension

ny: number of grid cells in the y dimension

nz: number of grid cells in the z dimension

xmin: x direction lower boundary (in code units)

ymin: y direction lower boundary (in code units)

zmin: z direction lower boundary (in code units)

xlen: x direction global domain length (in code units)

ylen: y direction global domain length (in code units)

zlen: z direction global domain length (in code units)

tout: final output time, in code units (see global.h)

outstep: time interval for output, in code units. In the case that more than one type of output file is defined, this will correspond to the most frequent output

gamma: ratio of specific heats, Cholla currently supports only a single gamma for all cells

init: name of initial conditions. Case sensitive. Current options include Constant, Sound_Wave, Square_Wave, Riemann, Shu_Osher, Blast_1D, KH, KH_res_ind, Rayleigh_Taylor, Implosion_2D, Gresho, Noh_2D, Noh_3D, Disk_2D, Disk_3D, Spherical_Overpressure_3D, Spherical_Overdensity_3D, Uniform, Zeldovich_Pancake, and Read_Grid. See initial_conditions.cpp for more information about each option. Sample input parameter files for many of these problems can be found in the examples directory.

outdir: path to output directory

Boundary Conditions

Given as a number, options include 1 (periodic), 2 (reflective), 3 (transmissive), 4 (custom). Can use different boundary conditions for each boundary

xl_bcnd: lower x boundary condition

xu_bcnd: upper x boundary condition

yl_bcnd: lower y boundary condition

yu_bcnd: upper y boundary condition

zl_bcnd: lower z boundary condition

zu_bcnd: upper z boundary condition

Optional Parameters

nfile: If the Read_Grid initial conditions are used, prefix for which file to read from.

indir: If the Read_Grid initial conditions are used, path to the directory where the input file can be found.

nfull: If slice or projection outputs are being used, set to define the multiple of outstep for full grid outputs to be made

custom_bcnd: If using a custom boundary condition, name of the boundary condition corresponding to the user-defined function, set in the Custom_Boundary function in boundary_conditions.cpp

prng_seed: The seed given to the pseudo random number generator (PRNG). If set to 0 then Cholla will generate a random seed. If set to non-zero then that will be used as the seed, making all results fully deterministic. At the time of writing the PRNG is only used for initializing particles.

Optional arguments for float32 single precision output

n_out_float32: For 0, disables f32 output. Otherwise, set to define the multiple of outstep for float32 outputs to be made

out_float_density: if > 0, Enables density field output

out_float_momentum_x: if > 0, Enables momentum_x field output

out_float_momentum_y: if > 0, Enables momentum_y field output

out_float_momentum_z: if > 0, Enables momentum_z field output

out_float_Energy: if > 0, Enables Energy field output

out_float_GasEnergy: if > 0, Enables GasEnergy field output

out_float_magnetic_x: if > 0, Enables magnetic_x field output

out_float_magnetic_y: if > 0, Enables magnetic_y field output

out_float_magnetic_z: if > 0, Enables magnetic_z field output

Needed for Rotated Projection Outputs

If the Makefile parameter ROTATED_PROJECTION is defined, the following parameters are needed. The rotation is about the delta axis.

delta: angle off the z-axis for projection

theta: angle off the y-axis for projection

phi: angle off the x-axis for projection

flag_delta: 1 or 2 - if 1, the assumption is that a complete grid output is being read in, and a set of rotated projections will be made corresponding to that snapshot; if 2, rotated projection outputs will be made as the simulation runs, with a frequency set by the outstep parameter

n_delta: if flag_delta is 1, how many files to output

ddelta_dt: if flag_delta is 2, how much to rotate the projection with each output; corresponds to a fraction of 2 $\pi$

Lx: Physical size (in code units) of the rotated projection output, horizontal direction

Lz: Physical size (in code units) of the rotated projection output, vertical direction

nxr: number of pixels of the rotated projection output, horizontal direction (recommended to use something slightly larger than the grid size, e.g. 1.5nx

nzr: number of pixels of the rotated projection output, vertical direction (recommended to use something slightly larger than the grid size, e.g. 1.5nz

Needed for Cosmology

If the Makefile parameter COSMOLOGY is defined, the following parameters are needed

scale_outputs_file:

Init_redshift:

End_redshift:

H0:

Omega_M:

Omega_L:

Needed for manual MPI grid

If the Makefile parameter SET_MPI_GRID is defined, the following parameters are needed

n_proc_x:

n_proc_y:

n_proc_z:

Needed for tiled initial conditions

If the Makefile parameter TILED_INITIAL_CONDITIONS is set, the following parameter is needed

tile_length:

Parameters used in some initial conditions functions

rho: density, in code units. Used in Constant, Sound_Wave, and Square_Wave initial conditions.

vx: x velocity, in code units. Used in Constant, Sound_Wave, and Square_Wave initial conditions.

vy: y velocity, in code units. Used in Constant, Sound_Wave, and Square_Wave initial conditions.

vz: z velocity, in code units. Used in Constant, Sound_Wave, and Square_Wave initial conditions.

P: pressure, in code units. Used in Constant, Sound_Wave, and Square_Wave initial conditions.

A: wave amplitude, used in Sound_Wave and Square Wave initial conditions

rho_l: left state density, in code units. Used in Riemann initial conditions.

vx_l: left state velocity in the X-direction, in code units. Used in Riemann initial conditions.

vy_l: left state velocity in the Y-direction, in code units. Used in Riemann initial conditions.

vz_l: left state velocity in the Z-direction, in code units. Used in Riemann initial conditions.

P_l: left state pressure, in code units. Used in Riemann initial conditions.

rho_r: right state density, in code units. Used in Riemann initial conditions.

vx_r: right state velocity in the X-direction, in code units. Used in Riemann initial conditions.

vy_r: right state velocity in the Y-direction, in code units. Used in Riemann initial conditions.

vz_r: right state velocity in the Z-direction, in code units. Used in Riemann initial conditions.

P_r: right state pressure, in code units. Used in Riemann initial conditions.

diaph: location of the initial discontinuity, in code units. Used in Riemann initial conditions.