[Numpy-discussion] could anyone check on a 32bit system?

[Matthew Brett]

Hi,

On Tue, Apr 30, 2013 at 9:16 PM, Matthew Brett <matthew.brett at gmail.com> wrote:
> Hi,
>
> On Tue, Apr 30, 2013 at 8:08 PM, Yaroslav Halchenko
> <lists at onerussian.com> wrote:
>> could anyone on 32bit system with fresh numpy (1.7.1) test following:
>>
>>> wget -nc http://www.onerussian.com/tmp/data.npy ; python -c 'import numpy as np; data1 = np.load("/tmp/data.npy"); print  np.sum(data1[1,:,0,1]) - np.sum(data1, axis=1)[1,0,1]'
>>
>> 0.0
>>
>> because unfortunately it seems on fresh ubuntu raring (in 32bit build only,
>> seems ok in 64 bit... also never ran into it on older numpy releases):
>>
>>> python -c 'import numpy as np; data1 = np.load("/tmp/data.npy"); print  np.sum(data1[1,:,0,1]) - np.sum(data1, axis=1)[1,0,1]'
>> -1.11022302463e-16
>>
>> PS detected by failed tests of pymvpa
>
> Reduced case on numpy 1.7.1, 32-bit Ubuntu 12.04.2
>
> In [64]: data = np.array([[ 0.49505185,  0.47212842],
>        [ 0.53529587,  0.04366172],
>        [-0.13461665, -0.01664215]])
>
> In [65]: np.sum(data[:, 0]) - np.sum(data, axis=0)[0]
> Out[65]: 1.1102230246251565e-16
>
> No difference for single vector:
>
> In [4]: data1 = data[:, 0:1]
>
> In [5]: np.sum(data1[:, 0]) - np.sum(data1, axis=0)[0]
> Out[5]: 0.0

Also true on current numpy trunk:

In [2]: import numpy as np

In [3]: np.__version__
Out[3]: '1.8.0.dev-a8805f6'

In [4]: data = np.array([[ 0.49505185,  0.47212842],
   ....:        [ 0.53529587,  0.04366172],
   ....:        [-0.13461665, -0.01664215]])

In [5]: np.sum(data[:, 0]) - np.sum(data, axis=0)[0]
Out[5]: 1.1102230246251565e-16

Not true on numpy 1.6.1:

In [2]: np.__version__
Out[2]: '1.6.1'

In [3]: data = np.array([[ 0.49505185,  0.47212842],
   ....:        [ 0.53529587,  0.04366172],
   ....:        [-0.13461665, -0.01664215]])

In [4]: np.sum(data[:, 0]) - np.sum(data, axis=0)[0]
Out[4]: 0.0

Cheers,

Matthew