#11 Improper indentation of OpenMP conditional compilation specification lines

[Meisam Tabriz]

According to the OpenMP API specifications [v5.2, §3.3.2 Free Source Form Conditional Compilation Sentinel] !$ is the conditional compilation sentinel in free form source files and can be used as:

!$ iam = omp_get_thread_num()

But the current version of findent (4.1.3) does not indent these lines correctly.

Example:

[input]

if (condition)
!$omp parallel
!$ num_threads = omp_get_num_threads()
!$omp end parallel
end if

[current behaviour]

if (condition)
 !$omp parallel
!$ num_threads = omp_get_num_threads()
 !$omp end parallel
end if

[desired output]

if (condition)
 !$omp parallel
 !$ num_threads = omp_get_num_threads()
 !$omp end parallel
end if

[Willem Vermin]

You forgot the THEN after the first line, but adding that does not change the output.

In the following I run findent with no flags.

When I run your example, (with added THEN), I get this:

if (condition) then
!$omp parallel
!$ num_threads = omp_get_num_threads()
!$omp end parallel
end if

The 'num_threads line was already correctly indented, so we see no change there. I get no leading space in lines 2 and 4. Strange.

Findent indents after the !$ sentinel, see the following example:

program p
if(.true.) then
!$ if(.true.) then
!$ print *,'OMP'
!$ end if
end if
end program

Findent indents this thusly:

program p
   if(.true.) then
!$    if(.true.) then
!$       print *,'OMP'
!$    end if
   end if
end program

Does this answer your question?

[Meisam Tabriz]

Thanks for your quick response. I guess my confusion arises from the fact that the indentation is done after the !$ sentinel but before the !$omp. So my code turns into something like:

    !$omp parallel shared(num_threads)
!$  num_thread = omp_get_num_threads()
    !$omp end parallel

Is there any way to make this consistent (to have indentation before both)?

[Willem Vermin]

Personally, I find the way findent handles !$ lines results in a better readable code than adding indent before !$. And I like to have the !$omp lines starting in column 1: these lines are not indented by findent.

Your suggestion would entail the following to be done by findent:

change a line like

  !$    continue

into

!$ continue

and then, indent this line as a whole, also indent !$omp lines, whether they start in column 1 or not. This is not a trivial change, practice learned me that there always nasty issues with continuation lines and such. Nevertheless, I will investigate the matter and let you know.

[Willem Vermin]

I have a solution for you that does not involve changing findent itself:

Create a script "myfindent":

1 2	#!/bin/sh findent "$@" | sed 's/!\$\([ &]\)\( *\)/\2!$\1/'

Given the following Fortran source:

program q
if(.true.) then
!$ if(.true.) then
!$ print *,'OMP', &
!$  'omp'
!$ end if
end if
end program

the following output is produced by "myfindent":

program q
   if(.true.) then
   !$ if(.true.) then
      !$ print *,'OMP', &
         !$ 'omp'
   !$ end if
   end if
end program

(one could say that the handling of continuation lines could be better...)
while findent produces:

program q
   if(.true.) then
!$    if(.true.) then
!$       print *,'OMP', &
!$          'omp'
!$    end if
   end if
end program

[Meisam Tabriz]

Thanks for your helps. I think I should be able to modify it to align the !$ and add space afterwards.