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c.f. bug 424647
List Archive: gentoo-amd64
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To: gentoo-amd64@g.o
From: Mark Knecht <markknecht@...>
Subject: Re: Possible Math Problem - Request For Verification [Solved]
Date: Sat, 25 Jun 2011 20:54:10 -0700
On Sat, Jun 25, 2011 at 8:44 PM, Frank Peters <frank.peters@...> wrote:
> On Sat, 25 Jun 2011 13:41:11 -0400
> Frank Peters <frank.peters@...> wrote:
>
>>
>> /tmp/fp-test-results/clib_DP.output: ucbtest UCBFAIL in cabsd at line 701 for double
>>
>
> The culprit seems to be GCC optimization.  If I run the test with either "-O0"
> or "-O1" flags I can eliminate the cabsd failure.  Using "-O2" or "-O3" will
> result in the cabsd error.
>
> However, I've used "-O2" previously and had no problems with this test.  Possibly,
> some of these new LTO and GRAPHITE capabilities of GCC are to blame, even though
> I do not compile the ucbtest with either LTO or GRAPHITE enabled.  But GCC has itself
> been compiled using LTO and GRAPHITE.
>
> Anyway, thanks for all who actually ran the test on their machines.  I was
> thinking of filing bug reports with GLIBC and GCC and that would have turned
> out to be foolish.  I did check the Changelogs for GLIBC and there doesn't seem
> to have been any modification of the cabs() code over the last several versions.
>
> Frank Peters

I'm using -O2 here on all my machines. Certainly it isn't that option
that causes a problem for everyone. Sounds like something specific to
your processor revision.

Take care,
Mark


Replies:
Re: Possible Math Problem - Request For Verification [Solved]
-- Frank Peters
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Possible Math Problem - Request For Verification
-- Frank Peters
Re: Possible Math Problem - Request For Verification [Solved]
-- Frank Peters
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Updated Jun 28, 2012

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