[Numpy-discussion] TypeError when using double , longdouble in numpy.dot
Charles R Harris
Wed Jul 7 23:59:32 CDT 2010
On Wed, Jul 7, 2010 at 10:13 PM, Christoph Gohlke <firstname.lastname@example.org> wrote:
> Dear NumPy developers,
> I am trying to solve some scipy.sparse TypeError failures reported in
>  and reduced them to the following example:
> >>> import numpy
> >>> a = numpy.array([])
> >>> numpy.dot(a.astype('single'), a.astype('longdouble'))
> array([[1.0]], dtype=float64)
> >>> numpy.dot(a.astype('double'), a.astype('longdouble'))
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: array cannot be safely cast to required type
Just for laughs, what happens if you reverse the order of the arguments?
Type promotion in numpy is not always symmetric.
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