https://stackoverflow.com/questions/3161564/how-can-i-visualize-fortran-90-or-later-source-code-e-g-using-graphviz https://stackoverflow.com/questions/3161564/h

https://stackoverflow.com/questions/3161564/how-can-i-visualize-fortran-90-or-later-source-code-e-g-using-graphviz https://stackoverflow.com/questions/3161564/how-can-i-visual... has some suggestions. I haven't tried any but am thinking of using Doxygen as described for some old Fortran77 code with lots of gotos since Understand is well outside of our budget. You're probably aware of this, but our biggest speed gains in some code we ported from DEC Fortran to gfortran was vectorizing loops. Best of luck.