https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104722
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> I think this code is undefined as the order of the addition is not specified
> for std::accumulate
It is specified for std::accumulate, but the _GLIBCXX_PARALLEL mode breaks the
guarantees by performing the additions in parallel, so not in the same order.
The parallel mode was an experiment that will be removed from libstdc++ at some
point. You might want to try the C++17 parallel algos instead, or just accept
that parallel mode evaluates the algorithm differently (that's the whole point
- it breaks the work into chunks to be evaluated in multiple threads).
