On Sat, Apr 20, 2019 at 12:24 AM C W <tmrs...@gmail.com> wrote: > > Am I miss reading something? Thank you in advance!
Hey, You are missing that the broadcasting rules typically apply to arithmetic operations and methods that are specified explicitly to broadcast. There is no mention of broadcasting in the docs of np.dot [1], and its behaviour is a bit more complicated. Specifically for multidimensional arrays (which you have), the doc says If a is an N-D array and b is an M-D array (where M>=2), it is a sum product over the last axis of a and the second-to-last axis of b: dot(a, b)[i,j,k,m] = sum(a[i,j,:] * b[k,:,m]) So your (3,4,5) @ (3,5) would want to collapse the 4-length axis of `a` with the 3-length axis of `b`; this won't work. If you want elementwise multiplication according to the broadcasting rules, just use `a * b`: >>> a = np.arange(3*4*5).reshape(3,4,5) ... b = np.arange(4*5).reshape(4,5) ... (a * b).shape (3, 4, 5) [1]: https://docs.scipy.org/doc/numpy/reference/generated/numpy.dot.html _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
