February 6, 2020 11:00 PM, "Henry Rich" <[email protected]> wrote:
> It's not so simple to describe. In fact, you haven't described it. > Your example seems to have a rank-4 array times a rank-5 array producing > a rank-7 array. Is this result the sum of rank-7 arrays created by > multiplying rank-3 times rank-4? I don't know how to make that jibe > with 'the usual multiplication of numbers', which applies to atoms. C_ijlmnop = sum_k A_ijkl * B_mknop means I have C with rank 7, A with rank 4 and B with rank 5. C_ijlmnop is a *number*, the same with A_ijkl and B_mknop (for any given set of allowed indices). The equation above determines all atoms of C (all components of C) as a function of atoms of A and B. The multiplication *is* between numbers (or atoms, if you like). [The prescription can also be understood as, first, making an outer product of A and B leading to rank-9 object, then contracting together 2 indices, leading to a rank-7 object (tensor).] What is not clear with this? > To start with I want to know: Does my example do what you want it to do? I will check if it does what I want. Thanks! Ruda ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
