2012/2/1 martin großhauser :

Hello,

when I try in my script to divide a masked array by a scalar I get an error. The instruction is:

...

...

sppa = sp / 100.

sp is a masked array with ndim = 3.

error is: Traceback (most recent call last):  File "/media/nethome/Work/workspace/interimEnso/src/mlBudget.py", line 95, in <module>    sppa = sp / 100.  File "/usr/lib/pymodules/python2.7/numpy/ma/core.py", line 3673, in __div__    return divide(self, other)  File "/usr/lib/pymodules/python2.7/numpy/ma/core.py", line 1072, in __call__    m |= ma ValueError: invalid return array shape

The interesting thing is that this error only occurs after a tiling instruction:

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        sp4d = N.tile(sp, (ninterf, 1, 1, 1))

If I do the division before the tiling I don't get an error. There's also no error if I do the division with N.divide(sp, 100.).

Also printing the array sp after tiling doesn't work, while it works before. If I debug the script with eclipse/PyDev, in the variables window I get the message "Unable to get repr for " for the sp array after tiling.

The tiling operation shouldn't change the array, should it? Is this a bug, or is it expected behaviour?

Regards, Martin Groszhauser

I forgot to mention that I'm using Numpy 1.5.1 from Ubuntu 11.04 (1.5.1-1ubuntu2).

Le 01/02/2012 21:09, Benjamin Root a écrit :

I can't reproduce this bug with the latest numpy from github master. Perhaps it has been fixed by now? Hi,

I've no idea what's going on, but here is my $0.02 contribution. I reproduced the bug (numpy 1.5.1) with a rather minimal script. See attached. Best, Pierre

On 02/02/2012 02:52 AM, martin großhauser wrote:

On Wed, Feb 1, 2012 at 10:57 PM, Pierre Haessig wrote:

...

I've no idea what's going on, but here is my $0.02 contribution. I reproduced the bug (numpy 1.5.1) with a rather minimal script. See attached. I reproduced the issue with Pierre's script also in numpy 1.6.1 and latest github (2.0.0.dev-b8bfcd0). In newer versions the error message is:

Traceback (most recent call last): File "ma_tiling_issue.py", line 18, in<module> a/100. #raises ValueError: invalid return array shape File "/usr/local/lib/python2.7/dist-packages/numpy/ma/core.py", line 3654, in __div__ return divide(self, other) File "/usr/local/lib/python2.7/dist-packages/numpy/ma/core.py", line 1078, in __call__ m |= ma ValueError: non-broadcastable output operand with shape (3,3,3) doesn't match the broadcast shape (1,3,3,3)

I still don't know what's going on. Is the internal representation (shape) of the array changed by the tile instruction?

I created a ticket: http://projects.scipy.org/numpy/ticket/2035 _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion This is triggered when the array's mask is not 'False' and appears to be due to the call on line 827 of numpy/lib/shape_base.py: c = _nx.array(A,copy=False,subok=True,ndmin=d)

where _nx is 'import numpy.core.numeric as _nx'. Also, setting 'copy=True' in the call does not change anything. You probably can get around it by passing a copy to np.tile(): sp4d = np.tile(a.copy(), (4, 1, 1, 1)) Bruce