Teaching and debugging OpenMP in gfortran (or otherwise!)

[Paul Richard Thomas]

Hi Nick,

One remark that I have is that your gfortran is rather out of date. A
lot of bugs that show up with valgrind have been fixed since then. The
second thought is that you might contact Jakub Jelnik for questions
concerning OpenMP debugging.

Cheers

Paul


On 15 September 2018 at 13:02, N.M. Maclaren <nmm1@cam.ac.uk> wrote:
> Sorry about this, but searching in the usual places has found nothing
> useful, and I am interested in gfortran's direction.
>
> The kiddies do not like my OpenMP course, because it is all about what not
> to do, but the problem is that even egregious data races do not show up in
> test codes and there doesn't seem to be a usable testing tool. The best for
> use with gfortran and gcc seems to be valgrind (helgrind or drd), but both
> produce a hopeless number of false positives even in gcc 4.9.4 rebuilt with
> no futexes and valgrind 3.13.  Interestingly, gfortran is worse than gcc,
> and my examples are functionally identical (I teach both languages at once).
>
> This isn't just a teaching problem, as OpenMP experts will know.  It's
> horribly common for programs to fail, sometimes, after long running times,
> on some systems - usually giving wrong answers with no diagnostic :-(
>
> Has anyone any comments on this - except "you're stuffed" :-)  I know the
> difficulty involved, so am not expecting a good solution, nor thinking
> about doing it, but is there even a partial solution to this for gfortran?
>
>
> Regards,
> Nick Maclaren.
>
>



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