Config files and command-line arguments

Table of Contents

• The config-fortran module
• Passing configuration files via the command line
• Setting variables from the command line
• Examples of a few important options
• A list of all options

The config-fortran module

Afivo-streamer uses the config_fortran module to allow users to customize simulations with different options. Each option has a name given by [group%]name, where the group can also be empty. Options can be specified in configuration files like this:

group%name = value

Multiple settings from the same group can be given like this:

[group]
    name = value
    name_2 = value_2

Options can be of type integer, real, logical or string. Some options are arrays, and they can also have a variable length.

In the source code, parameters are usually added with the CFG_add_get method, with the following syntax:

call CFG_add_get(cfg, name, variable, description)

For example, for the end_time variable, which is internally stored as ST_end_time:

real(dp) :: ST_end_time = 10e-9_dp
...
call CFG_add_get(cfg, "end_time", ST_end_time, "The desired endtime (s) of the simulation")

If the user does not set end_time, then it will retain its default value.

Passing configuration files via the command line

One or more configuration files can be specified when running a simulation:

./streamer file_1.cfg file_2.cfg ...

Options from later files will override those from earlier files.

Setting variables from the command line

Individual options can be specified via the command line:

./streamer file_1.cfg -var=value

If necessary, you can use quotes to specify for example an array:

./streamer file_1.cfg -var="a b c"

Examples of a few important options

name	example	meaning
output%name	output/my_sim	filename base for output files
output%dt	0.25e-9	time step for writing output
input_data%file	[filename]	input file with transport data and reactions
end_time	10e-9	end time of the simulation (s)
domain_len	32e-3 32e-3	length of the domain (m)
gas%components	N2 O2	names of the gas components
gas%fractions	0.8 0.2	gas fractions
gas%pressure	1.0	pressure (bar)
field_amplitude	2e6	amplitude of the background field (V/m)
cylindrical	T	Whether the simulation has an axisymmetric geometry
refine_adx	1.0	Parameter that controls the grid refinement (smaller means finer)

A list of all options

To obtain a list with all simulation options, first run a simulation. If the value for outputname is for example output/streamer_2d, then a file output/streamer_2d_out.cfg should be generated with all options and their values.