Alternatively, the library can also be run as a standalone using the previously mentioned ddx_driver. The program ddx_driver is a very simple Fortran code that performs two main functions: it performs the initialization from the file and then performs the steps given in 3.1. In this case, the initialization from the input file is done with a separate Fortran function called ddfromfile, which reads the text-based input file and then calls ddinit with appropriate parameters.