On 01/05/18 01:45, Allan Haldane wrote:
On 04/29/2018 05:46 AM, Matti Picus wrote:
In looking to solve issue #9028 "no way to override matmul/@ if
__array_ufunc__ is set", it seems there is consensus around the idea of
making matmul a true gufunc, but matmul can behave differently for
different combinations of array and vector:
(n,k),(k,m)->(n,m)
(n,k),(k) -> (n)
(k),(k,m)->(m)
Currently there is no way to express that in the ufunc signature. The
proposed solution to issue #9029 is to extend the meaning of a signature
so "syntax like (n?,k),(k,m?)->(n?,m?) could mean that n and m are
optional dimensions; if missing in the input, they're treated as 1, and
then dropped from the output" Additionally, there is an open pull
request #5015 "Add frozen dimensions to gufunc signatures" to allow
signatures like '(3),(3)->(3)'.
How much harder would it be to implement multiple-dispatch for gufunc
signatures, instead of modifying the signature to include `?` ?
There was some discussion of this last year:
http://numpy-discussion.10968.n7.nabble.com/Changes-to-generalized-ufunc-core-dimension-checking-tp42618p42638.html
That sounded like a clean solution to me, although I'm a bit ignorant of
the gufunc internals and the compatibility constraints.
I assume gufuncs already have code to match the signature to the array
dims, so it sounds fairly straightforward (I say without looking at any
code) to do this in a loop over alternate signatures until one works.
Allan
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I will take a look at multiple-dispatch for gufuncs.
The discussion also suggests using an axis kwarg when calling a gufunc
for which there is PR #1108 (https://github.com/numpy/numpy/pull/11018)
discussion).
Matti
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