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| From | Juergen Sauermann <juergen.sauermann@t-online.de> |
| Newsgroups | gnu.g++.bug |
| Subject | Error Report |
| Date | Sat, 16 Apr 2016 18:05:12 +0200 |
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Hi,
I habe received the error report below on the bug-apl mailing list.
But the problem seems to be with the g++ compiler.
The effect is that -8 to the 1/3-power (= cubic root of -8) gives the
correct result when compiled with -O2, but 0 with -O5.
See http://lists.gnu.org/archive/html/bug-apl/2016-04/index.html for the
entire thread.
Best Regards,
Jürgen Sauermann
> On Apr 13, 2016, at 7:03 PM, Kacper Gutowski<mwgamera@gmail.com> wrote:
>
> On Thu, Apr 14, 2016 at 1:54 AM, Xiao-Yong Jin wrote:
>> Exactly so. ‘-Ofast -fno-finite-math-only’ gives correct results.
>> What’s going on here? I don’t expect this has anything to do with NaN or Inf.
> pow(-8., 1./3) is nan.
> And -ffinite-math-only eliminates isfinite check at FloatCell.cc:422.
That explains it. Thanks.
Here is some amusement:
g++ -Ofast -fno-unsafe-math-optimizations:
pow(-8., 1./3.) => nan
isfinite => 1
g++ -Ofast -fno-unsafe-math-optimizations -fno-finite-math-only:
pow(-8., 1./3.) => nan
isfinite => 0
g++ -Ofast -fno-finite-math-only:
pow(-8., 1./3.) => -2
isfinite => 1
clang++ -march=native -Ofast:
pow(-8., 1./3.) => nan
isfinite => 0
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Error Report Juergen Sauermann <juergen.sauermann@t-online.de> - 2016-04-16 18:05 +0200
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