IRPF90 is a Fortran code generator. Schematically, the programmer only writes computation kernels, and IRPF90 generates the "glue code" that will link all these kernels together to produce the expected result, handling all the relationships between the variables. In this way, even large codes can still be under control.

IRPF90 (1.7.5) is free software under the GPL licence available on GitLab.