Test contiguous pointers

Hi Nick,

The 'contiguous' keyword appears in F2008, and its implementation is still subject to interpretation.
Here is a test file to explore things.

! Simple tests for "array temporaries" and the influence of:
!
! - the use of the "contiguous" keyword
! - the use of pointers instead of allocatable arrays or simple arrays
!
! Results:
!
! gfortran 5.2 (checks at compile time with -Warray-temporaries)
! (disable the call to is_contiguous, as it is not implemented...)
!
! The contiguous keyword has no effect.
! The use of pointers forces temporaries
! Non-contiguous sections are correctly flagged.
!
! intel 15.0.3 (checks at runtime). Use -check all -traceback
!
! The contiguous keyword is taken at face value, even if the
! case is obviously not contiguous, and no temporaries are produced.
! NOTE: According to Steve Lionel from Intel, this might have changed in recent
! versions
! (https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/508693#)
!
! On the other hand, the vanilla version of the routine correctly
! detects non-contiguous and contiguous cases (!!)

module m_interface
  CONTAINS
        SUBROUTINE MPI_BCAST( &
     & BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
          real, INTENT(INOUT) :: BUFFER(*)
          INTEGER, INTENT(IN) :: COUNT
          INTEGER, INTENT(IN) :: DATATYPE
          INTEGER, INTENT(IN) :: ROOT
          INTEGER, INTENT(IN) :: COMM
          INTEGER, INTENT(OUT) :: IERROR
          EXTERNAL MPI_BCAST_EXT
! CALL MPI_BCAST_EXT( &
! & BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
        END SUBROUTINE MPI_BCAST

              SUBROUTINE MPI_BCAST_CONT( &
     & BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
          real, INTENT(INOUT), contiguous :: BUFFER(:)
          INTEGER, INTENT(IN) :: COUNT
          INTEGER, INTENT(IN) :: DATATYPE
          INTEGER, INTENT(IN) :: ROOT
          INTEGER, INTENT(IN) :: COMM
          INTEGER, INTENT(OUT) :: IERROR
          EXTERNAL MPI_BCAST_EXT
          print *, is_contiguous(buffer)
! CALL MPI_BCAST_EXT( &
! & BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
        END SUBROUTINE MPI_BCAST_CONT
end module m_interface
!
program tt
  use m_interface

  integer, parameter :: n = 20
    real, dimension(n) :: a
    real, pointer :: b(:)

    real, dimension(n,n) :: c
    real, allocatable :: d(:)
    real, dimension(:,:), allocatable :: e

    integer :: root, comm, ierror, count, datatype

    allocate(b(n))
    allocate(d(n))
    allocate(e(n,n))

  root = 0
  datatype = 34
  comm = 333

  call mpi_bcast(a,n,datatype,root,comm,ierr)
  call mpi_bcast(b,n,datatype,root,comm,ierr)
  call mpi_bcast(c(2,:),n,datatype,root,comm,ierr) ! Not contiguous
  call mpi_bcast(c(:,2),n,datatype,root,comm,ierr)
  call mpi_bcast(d,n,datatype,root,comm,ierr)
  call mpi_bcast(e(2,:),n,datatype,root,comm,ierr) ! Not contiguous
  call mpi_bcast(e(:,2),n,datatype,root,comm,ierr)

  call mpi_bcast_cont(a,n,datatype,root,comm,ierr)
  call mpi_bcast_cont(b,n,datatype,root,comm,ierr)
  call mpi_bcast_cont(c(2,:),n,datatype,root,comm,ierr) ! Not contiguous
  call mpi_bcast_cont(c(:,2),n,datatype,root,comm,ierr)
  call mpi_bcast_cont(d,n,datatype,root,comm,ierr)
  call mpi_bcast_cont(e(2,:),n,datatype,root,comm,ierr) ! Not contiguous
  call mpi_bcast_cont(e(:,2),n,datatype,root,comm,ierr)

end program tt