Running Gerris through a debugger
Running Gerris through a debugger such as GDB particularly via a graphical front-end like DDD, as suggested in the programming course, is one way to find out exactly what the program is doing line by line.
Running Gerris through GDB
This is different to post-mortem debugging with GDB as suggested in the instructions for How to report bugs: for that GDB is called on a core-dump file. Here it's called with the binary and its arguments so the
--args flag is needed; i.e. GDB is launched by prepending
gdb --args to the Gerris command line; e.g.
$ gdb --args gerris2D vorticity.gfs
start the program and execute the
next line, one at a time...
(gdb) start (gdb) next