# Using and Porting GNU Fortran

### (1)

loop discovery refers to the process by which a compiler, or indeed any reader of a program, determines which portions of the program are more likely to be executed repeatedly as it is being run. Such discovery typically is done early when compiling using optimization techniques, so the "discovered" loops get more attention--and more run-time resources, such as registers--from the compiler. It is easy to "discover" loops that are constructed out of looping constructs in the language (such as Fortran's `DO`). For some programs, "discovering" loops constructed out of lower-level constructs (such as `IF` and `GOTO`) can lead to generation of more optimal code than otherwise.

### (2)

The files generated like this can also be used for inter-unit consistency checking of dummy and actual arguments, although the `ftnchek` tool from `ftp://ftp.netlib.org/fortran` or `ftp://ftp.dsm.fordham.edu` is probably better for this purpose.

### (3)

No, not that one.

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