On Wed, 8 Mar 2023, Thomas Koenig wrote:
> On 08.03.23 15:55, Paul Richard Thomas via Fortran wrote:
> > As noted below, rnflow.f90 hangs with the unpatched mainline at -O3 but
> > runs successfully at -O2.
>
> I can confirm that.
>
> > I presume that this is a serious regression since it involves optimization?
> > Which component should I post it against?
>
> Probably against tree-optimization. If later analysis determines that
> it is something else, people will reassign it.
>
> This one probably calls for bisection.
I have the following local change to rnflow with that I can't reproduce:
--- rnflow.f90.orig 2016-06-01 14:50:16.922376347 +0200
+++ rnflow.f90 2016-06-01 14:56:54.739045162 +0200
@@ -884,6 +884,7 @@
! generation maison d'une valeur pseudo-aleatoire uniforme sur (0,1)
!
integer, intent (inout) :: jsee ! germe courant
+ integer(kind=8) :: jsee_long
integer, parameter :: jmul = 843314861 ! multiplicateur
integer, parameter :: jadd = 453816693 ! constante additive
integer, parameter :: j230 = 1073741824 ! 2 puissance 30
@@ -899,7 +900,9 @@
!CRAY - The following multiply must be done with 64 bits (not 46 bits)
! The algoritm depends on the overflow characteristics of
! a 32 or 64 bit multiply.
- jsee = jsee * jmul + jadd
+ jsee_long = jsee;
+ jsee_long = jsee_long * jmul + jadd
+ jsee = jsee_long;
!CRAY - Change to avoid 32 bit integer dependency
!
! The original line is needlessly dependent on the
the existing comment already explains the issue. I suppose
-fdefault-integer-8 would also work around the issue?
ISTR there is an old (closed invalid) bugreport about this as well.
Richard.
