/em>.  For active variables declared a single matrix or
            array of matrices, the value written is the difference, in basic machine
            units, between the offsets of consecutive columns or rows in each matrix.
            For active variables not declared as a matrix or array of matrices, zero
            is written to <em class="parameter"><code>params</code></em>.  For active variables not backed by a buffer
            object, -1 is written to <em class="parameter"><code>params</code></e