[Bug fortran/42118] Slow forall

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42118

--- Comment #8 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Tobias Burnus from comment #7)
> By the way, the Fortran committee is considering to deprecate FORALL in the
> next standard (Fortran 2015) because it considers FORALL superior in nearly
> all aspects.

Change "FORALL" to "DO CONCURRENT" in the last line and "deprecate" to
"obsolescent". See http://j3-fortran.org/doc/year/13/13-323.txt

The proposal has not been accepted yet, but I also didn't see much opposition
to it. Quoting the reasoning (proposed for Appendix B of the next Fortran
standard):

"The FORALL construct and statement were added to the language
in the expectation that they would enable highly efficient
execution, especially on parallel processors.  However,
the experience with them indicates that they are too complex
and have too many restrictions for compilers to take
advantage of them.  They are redundant with the DO CONCURRENT
loop, and may of the manipulations for which they might be used
may be done more efficiently by use of pointers, especially
using pointer rank remapping."