[SciPy-User] [cython-users] bug report + feature request (was: scipy cblas return value)

[William Stein]

On Thu, Sep 26, 2013 at 11:35 AM, Arnaud Bergeron <abergeron at gmail.com> wrote:
> 2013/9/26 William Stein <wstein at gmail.com>
>>
>> On Thu, Sep 26, 2013 at 10:04 AM, Arnaud Bergeron <abergeron at gmail.com>
>> wrote:
>> > Or scipy is badly compiled.  Since OS X does not ship with a fortran
>> > compiler it is especially hard to compile and link it properly with a
>> > blas.
>> > If you use slightly incompatible compilers there is absolutely no
>> > compile
>> > error you just get broken results out of the blas functions.
>> >
>> > On that note the only prebuilt scipy that is not broken is the one that
>> > comes with Enthough Canopy.
>>
>> Are you saying that the prebuilt scipy we ship with Sage is broken?
>> I'm curious, since I can file a bug report, and I thought we had
>> things sorted out by now, after putting a heck of a lot of work into
>> this platform over the last 6 years...  Here's our Mac binaries:
>>
>>
>> http://boxen.math.washington.edu/home/sagemath/sage-mirror/osx/intel/index.html
>
>
> Sage isn't just a python distribution :)  It's also not listed on the scipy
> install page.

OK, good point :-)

>
> But still, the scipy binaries that come with it are broken (at least for the
> 10.6 package I tried).  If you try the command above it returns -0.0 rather
> than the correct 0.09999999403953552.

Ugh.  Many thanks for the bug report.

>
>
>>
>> Here's the source, which I think automatically gets things right
>> (regarding building scipy), assuming one follows the instructions...
>>
>>
>> http://boxen.math.washington.edu/home/sagemath/sage-mirror/src/index.html
>>
>>  --William
>>
>>
>> >  The Anaconda one is broken.  I haven't tried
>> > the standalone packages, though.
>> >
>> >
>> > 2013/9/26 Sturla Molden <sturla at molden.no>
>> >>
>> >>
>> >> On Sep 26, 2013, at 3:09 PM, Radim Řehůřek <me at radimrehurek.com> wrote:
>> >>
>> >> > I guess I was too verbose, let me rephrase:
>> >> >
>> >> > 1. BUG REPORT
>> >> > `scipy.linalg.blas.sdot` gives wrong results on mac:
>> >> >
>> >> > >>> scipy.linalg.blas.sdot(np.array([ 10.], dtype=np.float32),
>> >> > >>> np.array([ 0.01], dtype=np.float32))
>> >> > -0.0
>> >> >
>> >>
>> >> Let me submit in evidence to the contrary:
>> >>
>> >> In [20]:
>> >>
>> >> scipy.linalg.blas.sdot(np.array([10.],dtype=np.float32),np.array([0.01],dtype=np.float32))
>> >> Out[20]: 0.09999999403953552
>> >>
>> >> In [21]: sys.platform
>> >> Out[21]: 'darwin'
>> >>
>> >> It is your BLAS library that makes the error, not SciPy.
>> >>
>> >>
>> >> Sturla
>> >>
>> >> --
>> >>
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>> >
>> >
>> >
>> > --
>> > La brigade SnW veut vous recruter - http://www.brigadesnw.ca
>> >
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>>
>> --
>> William Stein
>> Professor of Mathematics
>> University of Washington
>> http://wstein.org
>>
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>>
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-- 
William Stein
Professor of Mathematics
University of Washington
http://wstein.org