[SciPy-Dev] seeded randn gets different values on osx

Vincent Davis vincent@vincentdavis....
Sun Jun 13 12:32:29 CDT 2010


On Sun, Jun 13, 2010 at 11:29 AM, Charles R Harris <
charlesr.harris@gmail.com> wrote:

>
>
> On Sun, Jun 13, 2010 at 11:17 AM, Vincent Davis <vincent@vincentdavis.net>wrote:
>
>> On Sun, Jun 13, 2010 at 9:46 AM, Matthew Brett <matthew.brett@gmail.com>wrote:
>>
>>> Hi,
>>>
>>> >> After a little discusion with Josef here are some results. It appears
>>> >> to me that osx gets different values from a seeded randn
>>> >
>>> >> On my machine OSX py 2.6.5, numpy 1.4.0 scipy 8.0b
>>> >>>>>> np.random.seed(0)
>>> >>>>>> np.random.randn(3)
>>> >>> array([ 0.06897149,  1.32078057,  1.5997924 ])
>>>
>>> Nor in a numpy-1.4.0 virtualenv:
>>>
>>> In [1]: import numpy as np
>>>
>>> In [2]: np.__version__
>>> Out[2]: '1.4.0'
>>>
>>> In [3]: np.random.seed(0)
>>>
>>> In [4]: np.random.randn(3)
>>> Out[4]: array([ 1.76405235,  0.40015721,  0.97873798])
>>>
>>
>> I just built 2.6 from current daily snapshot and installed numpy. Now I
>> get the right answer
>>
>> MacBookPro-new-2:~ vmd$ py26
>> Python 2.6.5+ (release26-maint, Jun 13 2010, 10:02:04)
>> [GCC 4.2.1 (Apple Inc. build 5659)] on darwin
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> import numpy
>> >>> import numpy as np
>> >>> np.random.seed(0)
>> >>> np.random.randn(3)
>> array([ 1.76405235,  0.40015721,  0.97873798])
>>
>> So I guess there is something wrong with the enthought 6.2 dist.
>>
>> Should there be a test added for this type of error?
>>
>>
> Yes, open a ticket. Strictly speaking we should probably test all the
> distributions, but just having something for the uniform and normal
> distributions would be a good start. They don't need to be long, just
> picking a seed (42?) and generating a couple of values should be sufficient.
> The floating results can't be expected to be exact due to various hardware
> floating implementations, but they should be exact to a reasonable number of
> figures.
>
> Ok I will file a ticket. I actually feel qualified to make a patch/test.

Vincent

Chuck
>
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  *Vincent Davis
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