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Error Report
From: |
Juergen Sauermann |
Subject: |
Error Report |
Date: |
Sat, 16 Apr 2016 18:05:12 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
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<address@hidden> 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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