The program starts execution in the main function in src/OpenMPCD/main.cpp. There, the command line arguments are parsed (run openmpcd with the --help flag for more information), and the run function is called, which controls the rest of the program execution.

There, the signal handler is installed. Then, the run directory is created if it does not exist already; if it does exist already, it is checked whether it is empty, except for config.txt, which, if present, is taken to be the configuration file (as opposed to the default config.txt relative to the working directory, i.e. the directory the openmpcd executable was launched from), and an input directory, which may contain arbitrary input data for the simulation, e.g. initial particle configurations. The path to the run directory can be specified on the command line, and defaults to runs/YYYY-MM-DD_hh:mm:ss, where YYYY is the year, MM the month, DD the day, hh the hour in 24-hour format, mm the minute, and ss the second the simulation has started.

Then, instances of OpenMPCD::CUDA::Simulation and OpenMPCD::CUDA::Instrumentation are constructed, reading the configuration file in the process.

After that, the simulation performs warmup steps (if configured), and performs sweep-measure-cycles, until either the configured number of sweeps have been performed, or the maximum runtime (as given on the command line) has been reached, whichever comes first.

Finally, the measured data and simulation metadata are saved to the run directory.