Re: Using external subroutines in OpenMP?

On Apr 26, 6:12 am, Sebastian Hanigk <han...@[EMAIL PROTECTED]
> wrote:
> jomarbue...@[EMAIL PROTECTED]
 writes:
> > Can someone clue me on how to call external subroutines from within a
> > parallel construct? As I understand, the OpenMP standard states that
> > all variables local to subroutines and functions within a parallel
> > construct are private.
>
> Essentially your called routines should be thread-safe (reentrant),
> i.e. no external state, global data access secured with mutexes, ...
>
> Write those routines like you would write subprograms in a functional
> language (no side effects, result depends only on passed arguments, no
> argument modification) and you get reentrancy for free.
>
> Sebastian

Dear Sebastian,

Thank you for your answer. The subroutines are indeed written in as
functional language. They are old Fortran 77 subroutines translated to
Fortran 90. The subroutines us neither "save" nor "common" (or modules
either). As you suggest the subroutines and main program are compiled
as reentrant ("-reentrancy threaded" in the ifort compiler) and the
results depend only on the passed arguments. However, one of the
purposes of the subroutines is in-place computation. One of the
arguments has to be changed by the subroutine. This is one of the
reasons I use the copy-in, copy-out approach giving each thread a
private array or a different ****tion of an array declared shared.
Neither approached worked.

Thanks again for your suggestions.

Jomar