FX,
>
>
> I'm ashamed that revision 118492
> (http://gcc.gnu.org/viewcvs?view=rev&revision=118492), which
> introduced this performance regression, is the MOD/MODULO patch by
> Paul Thomas and myself.
I realised from looking at the code for ac.f90, whilst on the plane last
night, that this must be the case. ac.f90 hinges on the random number
generator, which uses MOD.
I don't think that we should be ashamed about it. 32bit systems are
fine; I checked the Polyhedron suite before submitting and was
disappointed that it seemed to have little or no effect, other than
correcting the original PR!
Evidently there is something not very clever with the 64bit library.
Can Uros advise, please? In fact, is there a -ffast-math version
available or is it resorting to the ordinary library version? Detecting
the presence or not of the fast version, was what stopped me from
implementing this patch for so long.