fortran - OpenMP Several "shared"-directives?

Question

Hey there, I have a very long list of shared variables in OpenMP so I have to split lines in fortran and use the "&"-syntax to make sure the lines stick together!

Something like that:

!$OMP PARALLEL DEFAULT(private) SHARED(vars....,
     & more_vars...,
     & more_vars...
     & )

That gives me errors when compiling without OpenMP, since only the first like is recognized as a comment! The problem now is that I can't add a "!" in front of those lines with a "&" in front to support compiling without OpenMP:

!$OMP PARALLEL DEFAULT(private) SHARED(vars....,
!     & more_vars...,
!     & more_vars...
!     & )

because than it doesn't compile with OpenMP anymore... But I want to support both sorts of compiling in just one code... Any advices on how to do it?

Answer 1

You are not using the correct syntax. If you look at the OpenMP V3.0 specification, section 2.1.2 Free Source Form Directives, you will see the following:

The sentinel can appear in any column as long as it is preceded only by white space (spaces and tab characters). It must appear as a single word with no intervening character. Fortran free form line length, white space, and continuation rules apply to the directive line. Initial directive lines must have a space after the sentinel. Continued directive lines must have an ampersand as the last nonblank character on the line, prior to any comment placed inside the directive. Continuation directive lines can have an ampersand after the directive sentinel with optional white space before and after the ampersand.

So the correct form should be:

!$OMP PARALLEL DEFAULT(private) SHARED(vars...., &
!$OMP& more_vars..., &
!$OMP& more_vars...  &
!$OMP& )

For fixed form, it is the same type of thing. You start each line with the OMP sentinel and make sure continuation lines have a non-blank and non-zero character in column 6.