Stack is not a generalized ufunc. It may behave similar to one in many ways, but implementation wise has nothing to do with ufuncs. Also ufuncs do not support an arbitrary number of operands.
`vectorize` can indeed mimic generalized ufuncs, but (unfortunately) doesn't create them as such currently. - Sebastian On Tue, 2024-12-31 at 10:20 -0600, Jim Pivarski via NumPy-Discussion wrote: > I think you're right: the function `stack`, as you've defined it, is > a > gufunc. > > Here's an implementation using np.vectorize > < > https://numpy.org/doc/stable/reference/generated/numpy.vectorize.html> > (rather than nb.vectorize > <https://numba.readthedocs.io/en/stable/user/vectorize.html>). Since > the > signature is not "()->()" or "(),()->()" (or similar with a different > number of scalar inputs and scalar outputs), it's a generalized > ufunc. > > > > > def stack(a, b): > > ... broadcasts = np.broadcast_arrays(a, b) > > ... return np.stack(broadcasts, axis=-1) > > ... > > > > > stacky = np.vectorize(stack, signature="(),()->(2)") > > > > > stacky(np.arange(5), np.arange(5)) > > array([[0, 0], > > [1, 1], > > [2, 2], > > [3, 3], > > [4, 4]]) > > > > > stacky(np.arange(5), np.array([[1], [2], [3], [4], [5]])) > > array([[[0, 1], > > [1, 1], > > [2, 1], > > [3, 1], > > [4, 1]], > > > [[0, 2], > > [1, 2], > > [2, 2], > > [3, 2], > > [4, 2]], > > > [[0, 3], > > [1, 3], > > [2, 3], > > [3, 3], > > [4, 3]], > > > [[0, 4], > > [1, 4], > > [2, 4], > > [3, 4], > > [4, 4]], > > > [[0, 5], > > [1, 5], > > [2, 5], > > [3, 5], > > [4, 5]]]) > > > > On Tue, Dec 31, 2024 at 2:44 AM john.a.dawson--- via NumPy-Discussion > < > numpy-discussion@python.org> wrote: > > > Is the function `stack` above a gufunc? > > _______________________________________________ > > NumPy-Discussion mailing list -- numpy-discussion@python.org > > To unsubscribe send an email to numpy-discussion-le...@python.org > > https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ > > Member address: jpivar...@gmail.com > > > _______________________________________________ > NumPy-Discussion mailing list -- numpy-discussion@python.org > To unsubscribe send an email to numpy-discussion-le...@python.org > https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ > Member address: sebast...@sipsolutions.net _______________________________________________ NumPy-Discussion mailing list -- numpy-discussion@python.org To unsubscribe send an email to numpy-discussion-le...@python.org https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ Member address: arch...@mail-archive.com
