Re: Strange results with -mfpmath=sse

[Arjen Markus <arjen dot markus895 at gmail dot com>]

Hello Dominque,

it was exactly this thread that inspired me to have a look again at this program
(or a variant thereof - an example I have been using for in-house
courses for the
past couple of years). I replied to it with the test results - some
combinations
of flags give exactly the sort of things I would expect (not
necessarily the ones
I regard as correct), but this particular combination was way off!

(I realised there is a bug in 10.0**i when I saw NaNs for double-precision with
-ffloat-store, but the numbers reported here are, uh, weird)

Regards,

Arjen

2009/5/1 Dominique Dhumieres <dominiq@lps.ens.fr>:
> Arjen,
>
> I am not an expert with *86 architecture, but your problem seems
> related to the "extended floats" in the legacy *87. You may have a look to
>
> http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/4bca729841ee871a#
>
> and the pointer therein.
>
> Another point is that the lines
>
> x = 10.0 ** i
> y = - 10.0 ** i
>
> should be changed to use 10.0_wp, otherwise you are using real(4) for the rhs.
>
> Cheers
>
> Dominique
>