[Numpy-discussion] numpy.dot gives wrong results with floats?
Zachary Pincus
zpincus at stanford.edu
Wed Mar 1 01:07:02 EST 2006
Hi folks,
I'm using numpy 0.95 and came across an odd error with numpy.dot and
degenerate 2D floating-point arrays. See below for an illustration.
In [1]: import numpy
In [2]: numpy.version.version
Out[2]: '0.9.5'
In [3]: numpy.dot([[5]],[[1,1,1]]) # 2D int case OK
Out[3]: array([[5, 5, 5]])
In [4]: numpy.dot([[5.]],[[1,1,1]]) # 2D float case: what???
Out[4]: array([[ 5.00000000e+000, 4.46601253e-316,
5.42111867e-306]])
In [5]: numpy.dot([5.],[1,1,1]) # 1D float case OK
Out[5]: array([ 5., 5., 5.])
In [6]: numpy.dot([[[5.]]],[[[1,1,1]]]) # 3D float case OK
Out[6]: array([[[[ 5., 5., 5.]]]])
Zach
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