The function output_parameters() creates a file called info_ext that contains information about the parameters used in the run. The information is divided into three parts.
First, there is model specific information. For this output_parameters() simply calls a function called modelinfo() in the file model.h. The purpose of this function is to allow you to store whatever run-specific information you want for any particular model. We recommend as a minimum using this function to output the name of your model and a brief description (e.g. the equation for the potential) as well as the values of any coupling constants or other parameters of your model.
Second, there are general run parameters. These are the number of grid points, the number of dimensions, the number of fields, the size of the box (in distance units), the size of the time step, and the type of expansion used (full, power-law, or none).
Finally, this output file contains information about when the run occurred and how long it took. At the beginning and end of the run the date and time are recorded, and at the end the difference is calculated to give the total elapsed clock time. This information is useful for comparing timing on different machines or for different parameter values, or for simply reminding yourself at a later time how long to expect a run to take.