# Adding a run-time configuration parameter¶

The SPARTA run-time configuration contains any user-defined parameter that does not need to be set at compile-time. If this parameter is specific to a result or analysis, much of its treatment is confined to the respective code files, leading to a different treatment as described below.

## Adding a parameter for a result or analysis¶

Follow these steps to add a general configuration parameter that is specific to a result or an analysis:

• src/global.h

• Define the new parameter in the ConfigData struct.

• src/config.c

• In readConfigFile(), add an else if switch looking for the new parameter. Make sure to use the correct conversion from string to the format, e.g. atof or atoi etc. The identifier string used in the config file should ideally be the same as the name of your variable within the ConfigData struct to avoid confusion.

• src/results/result_xxx.c or src/analyses/analysis_xxx.c

• There will be a function initConfigResultXxx or initConfigAnalysisXxx, and within this function a number of steps are treated.

• Under CONFIG_INIT_STEP_DEFAULT, set the default values of your configuration parameters. Any parameter should have a default unless you want to force the user to set the parameter manually, in which case you must check that they did so (see below); otherwise the parameter will be undefined.

• Under CONFIG_INIT_STEP_CHECK, check that the user’s input makes sense (e.g., no negative numbers). This step can be omitted, but should be as strict as possible/necessary. This step happens directly after the config file is read.

• Under CONFIG_INIT_STEP_CONFIG, you can analyze the given config parameters in detail. The difference to CONFIG_INIT_STEP_CHECK is that, by now, SPARTA has analyzed the rest of the config and the simulation, including cosmology, the number of snapshots and so on.

• Under CONFIG_INIT_STEP_PRINT, add a line where you print the value of the new config parameter to the console. Please pay attention to the format (int/float/string, and if float, a sensible number of significant digits).

• There should be a function called outputConfigResultXxx or outputConfigAnalysisXxx, and if not, you should create it and link it to the properties of your result or analysis (see Adding a result module or Adding an analysis module). In this function, add a command to output your parameter, which will look something like:

hdf5WriteAttributeFloat(grp, "anl_xxx_my_param", config.anl_xxx_my_param);


See the HDF5 unit in src/io/io_hdf5.c for details on the different output functions. Note that your parameter will automatically be written into the correct place in the output file.

• docs/source/rs_xxx.rst or docs/source/al_xxx.rst

• Add the new parameter to the table that lists config parameters or create such a table. Specify its default value and add a brief explanation.

• config/sparta_complete.cfg and config/sparta.cfg

• Add the new parameter and its default value to the complete, default config file. This file makes it easier for the user to have a starting point and adjust parameters to their needs. If you think your parameter is important enough to be frequently changed by the user, also add it to sparta.cfg.

## Adding a general parameter¶

Follow these steps to add a general configuration parameter that is not specific to a result or an analysis. Note that you should only need to do this if you are working on the SPARTA framework itself! Any parameters related to plugins, i.e., results and analyses, should be contained within those units.

• src/global.h

• Define the new parameter in the ConfigData struct.

• Define a default for the parameter in the appropriate section near the top of the file. Most parameters should have defaults; if no default is set, the parameter could end up being undefined unless a check for invalid settings is added (see below).

• src/config.c

• In setDefaultConfig(), set the parameter to the default value.

• In readConfigFile(), add an else if switch looking for the new parameter. Make sure to use the correct conversion from string to the format, e.g. atof or atoi etc. The identifier string used in the config file should ideally be the same as the name of your variable within the ConfigData struct to avoid confusion.

• In checkConfig(), if necessary add an assert to check for nonsense values of the new parameter. This helps to avoid a lot of silly problems later!

• In printConfig(), add the new parameter to the printed output. Please pay attention to the format (int/float/string, and if float, a sensible number of significant digits).

• src/io/io_output.c

• In writeConfig(), add a command to output your parameter, which will look something like:

hdf5WriteAttributeFloat(grp, "my_param", config.my_param);


See the HDF5 unit in src/io/io_hdf5.c for details on the different output functions.

• docs/source/run_config.rst

• Add the new parameter to the table, specify its default value, and add a brief explanation.

• config/sparta.cfg

• Add the new parameter and its default value to this complete, default config file. This file makes it easier for the user to have a starting point and adjust parameters to their needs. If you think your parameter is important enough to be frequently changed by the user, also add it to sparta.cfg.

You may notice that all of the routines above as well as the documentation and defaults follow the same order, please make sure you stick to this order.