[Bug fortran/62007] New: default(none) conflicts with iteration variable in openmp parallel loop simd

[Bug fortran/62007] New: default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

            Bug ID: 62007
           Summary: default(none) conflicts with iteration variable in
                    openmp parallel loop simd
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alexander.grund at mailbox dot tu-dresden.de

If you use the "default(none)" clause in a parallel loop simd construct
gfortran will complain about having not set the iteration variable in a
private/shared clause:
" error: 'i_ct' not specified in enclosing parallel"

If you however do specify it in a private clause, gfortran will yield:
"Error: !$OMP PARALLEL DO SIMD iteration variable present on clause other than
LINEAR at (1)"

Trivial example:
!$omp parallel do simd default(none)
    do i_ct = 1, 10
      ...
    end do

If you use a "normal" parallel do both variants work.

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

Alexander Grund <alexander.grund at mailbox dot tu-dresden.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |major

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2014-08-04
     Ever confirmed|0                           |1
           Severity|major                       |normal

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Could you provide a complete test code?

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

--- Comment #3 from Alexander Grund <alexander.grund at mailbox dot tu-dresden.de> ---
Created attachment 33233
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33233&action=edit
Broken example

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

--- Comment #2 from Alexander Grund <alexander.grund at mailbox dot tu-dresden.de> ---
Created attachment 33232
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33232&action=edit
Working example

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

--- Comment #4 from Alexander Grund <alexander.grund at mailbox dot tu-dresden.de> ---
I attached 2 testcases. Both are the same files but with different file
endings. The .f works, the .F90 doesn't (it shows the reported behavior)

compile both with "gfortran -fopenmp {file}"

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[anlauf at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

Harald Anlauf <anlauf at gmx dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |anlauf at gmx dot de

--- Comment #5 from Harald Anlauf <anlauf at gmx dot de> ---
(In reply to Alexander Grund from comment #4)
> I attached 2 testcases. Both are the same files but with different file
> endings. The .f works, the .F90 doesn't (it shows the reported behavior)
> 
> compile both with "gfortran -fopenmp {file}"

The reason you get no error with the .f file is that it is
a Fortran fixed format source file.

If you add -ffree-form to the gfortran options, you get the
same error.

I think the problem is that the simd directive belongs to
OpenMP 4.0 and your gfortran supports only 3.1.

You'll have to wait until OpenMP 4 is supported by gfortran.

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[alexander.grund at mailbox dot tu-dresden.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

--- Comment #6 from Alexander Grund <alexander.grund at mailbox dot tu-dresden.de> ---
gfortran 4.9.1 supports OpenMP 4.0

Removing the default(none) clause removes the error message, so it certainly IS
supported.
Besides that: Even the error message mentiones "!$OMP PARALLEL DO SIMD" so it
is recognized.

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #7 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
% cat pr62007_db.f
       program hello
          integer :: i, x
C$omp parallel do simd private(x) default(none)
          do i=1,10
            x=x+1
          end do
       end program hello

triggers the same error.

[Bug fortran/62007] default(none) conflicts with iteration variable in openmp parallel loop simd

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62007

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I think the message is correct, or at least the case is highly unclear, the
OpenMP 4.0 standard has various unclear corner cases.
The thing is, the loop iterator is predetermined linear, and the linear clause
makes implicit reference to the outer var, but as linear clause is not allowed
on the parallel, it can't be specified there and with default(none) you are
requesting that everything is specified there explicitly.
I can only suggest using non-combined construct in that case if you for some
reason need default(none), say:
!$omp parallel private (i_ct) default(none)
!$omp do simd
  do i_ct = 1, 10
    ...
  end do
!$omp end parallel
or so.