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[Bug libstdc++/40852] [parallel-mode] parallel sort run time increases ~10 fold when vector size gets over ~4*10^9
- From: "singler at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 22 Oct 2009 16:41:17 -0000
- Subject: [Bug libstdc++/40852] [parallel-mode] parallel sort run time increases ~10 fold when vector size gets over ~4*10^9
- References: <bug-40852-8473@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #16 from singler at gcc dot gnu dot org 2009-10-22 16:41 -------
(In reply to comment #14)
> (In reply to comment #10)
>
> > However, I do not fully trust the double arithmetics yet, although some test
> > cases work. Does anybody else know a better way to avoid an overflow in ((a *
> > b) / c) with only integer arithmetics and normal rounding?
>
> you can use a 128-bit integer type on x86-64.
Very good idea.
Do you know a good #ifdef clause to check its availability. Is it really just
x64-64?
Also, I probably want to use it only when really needed, because I assume it to
be implemented in software, in particular the division.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40852