[Numpy-discussion] Warnings not raised by np.log in 32 bit build on Windows

Nathaniel Smith njs@pobox....
Fri Aug 23 07:29:13 CDT 2013


Probably the thing to do for reliable behaviour is to decide on the
behaviour we want and then implement it "by hand". I.e., either clear the
FP flags inside the ufunc loop (if we decide that log shouldn't raise a
warning), or else check for nan and set the invalid flag ourselves.
(Checking for nan should be much cheaper than computing log, I think, so
this should be okay speed-wise?)
On 23 Aug 2013 13:16, "Charles R Harris" <charlesr.harris@gmail.com> wrote:

> These things may depend on how the compiler implements various calls. Some
> errors went the other way with Julian's SIMD work, i.e., errors getting set
> that were not set before. I'm not sure what can be done about it.
>
>
> On Thu, Aug 22, 2013 at 8:32 PM, Warren Weckesser <
> warren.weckesser@gmail.com> wrote:
>
>> I'm investigating a test error in scipy 0.13.0 beta 1 that was
>> reported by Christoph Gohlke.  The scipy issue is here:
>> https://github.com/scipy/scipy/issues/2771
>>
>> I don't have a Windows environment to test it myself, but Christoph
>> reported that this code:
>>
>> ```
>> import numpy as np
>>
>> data = np.array([-0.375, -0.25, 0.0])
>> s = np.log(data)
>> ```
>>
>> does not generate two RuntimeWarnings when it is run with numpy 1.7.1
>> in a 32 bit Windows 8 environment (numpy 1.7.1 compiled with Visual
>> Studio compilers and Intel's MKL).  In 64 bit Windows, and in 64 bit
>> linux, it generates two RuntimeWarnings.
>>
>> The inconsistency seems like a bug, possibly this one:
>> https://github.com/numpy/numpy/issues/1958.
>>
>> Can anyone check if this also occurs in the development branch?
>>
>> Warren
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>
>
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