inner product

inner product $\cdot$

Computes

$\begin{displaymath} z_{i_1,\ldots,i_{r_x-1},j_1,\ldots,j_{r_y-1}} = \sum_k x_{... ..._{a-1},k,i_{a+1}\ldots,i_{r_x-1}} y_{j_1,\ldots,j_{r_y-1},k}, \end{displaymath}$

where

is the given axis, and

and

are the ranks of

and

respectively.