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)'.
I would like extending ufunc signature handling to implement both these
ideas, in a way that would be backwardly-compatible with the publicly
exposed PyUFuncObject. PyUFunc_FromFuncAndDataAndSignature is used to
allocate and initialize a PyUFuncObject, are there downstream projects
that allocate their own PyUFuncObject not via
PyUFunc_FromFuncAndDataAndSignature? If so, we could use one of the
"reserved" fields, or extend the meaning of the "identity" field to
allow version detection. Any thoughts?
Any other thoughts about extending the signature syntax?
Thanks,
Matti
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