>> I also note that for complex numbers, `vecmat` is defined as `x†A`, >> i.e., the complex conjugate of the vector is taken. This seems to be the >> standard and is what we used for `vecdot` too (`x†x`). However, it is >> *not* what `matmul` does for vector-matrix or indeed vector-vector >> products (remember that those are possible only if the vector is >> one-dimensional, i.e., not with a stack of vectors). I think this is a >> bug in matmul, which I'm happy to fix. But I'm posting here in part to >> get feedback on that. > > Does matmul not mean "matrix multiplication"? > > There is no conjugation in matrix multiplication. > > Have I misunderstood what matmul is supposed to be? (If it does mean > anything other than matrix multiplication then it is an extremely poor > choice of name.)
Right now, there is this weird special-casing of one-1 arguments which are treated as vectors that are promoted to matrices [1]. I agree that it is illogical to have, which is why I had the postscript about removing it from np.matmul, and instead letting `@` call vecdot, vecmat, matvec, or matmul as appropriate. -- Marten [1] From the docstring of np.matmul """ ... The behavior depends on the arguments in the following way. - If both arguments are 2-D they are multiplied like conventional matrices. - If either argument is N-D, N > 2, it is treated as a stack of matrices residing in the last two indexes and broadcast accordingly. - If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed. - If the second argument is 1-D, it is promoted to a matrix by appending a 1 to its dimensions. After matrix multiplication the appended 1 is removed. """ Note that the description is consistent with the current behaviour, but I don't think it is correct (certainly for two 1-d arguments) and my suggestion corresponds to changing the third item to, - If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions and taking the conjugate if complex. After matrix multiplication the prepended 1 is removed. _______________________________________________ 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
