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BUG: ufunc shape (1, ) aliased operands #8273

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mattharrigan opened this issue Nov 13, 2016 · 2 comments
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BUG: ufunc shape (1, ) aliased operands #8273

mattharrigan opened this issue Nov 13, 2016 · 2 comments
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@mattharrigan
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mattharrigan commented Nov 13, 2016 •
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>>> x = np.ones(10)
>>> np.add(x,x[:1],x)
array([ 2.,  3.,  3.,  3.,  3.,  3.,  3.,  3.,  3.,  3.])
>>> x = np.ones(10)
>>> np.add(x,x[4:5],x)
array([ 2.,  2.,  2.,  2.,  2.,  2.,  2.,  2.,  2.,  2.])

The first makes sense, but I expected the second to end with a string of 3's. Not totally sure if this is a bug or if aliased ufunc operands is documented as undefined behaviour somewhere.

The above was produced using the current master and ubuntu. On another windows machine with 1.10.4 I get even weirder:

>>> np.add(x,x[4:5],x)
array([ 2.,  2.,  2.,  2.,  2.,  2.,  2.,  2.,  2.,  3.])
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pv commented Nov 13, 2016

duplicate of gh-1683

@pv pv closed this as completed Nov 13, 2016
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pv commented Nov 13, 2016 •
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The short answer is that ufunc operations on aliased input/output is undefined.

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