[KRAKRISMOTT]

Sure it doesn't sum the whole matrix but it does sum row by row. Also how did you type out LaTeX in HN? Or is that a font?

[kragen]

it sums products, but convolution is summing products in a particular way that is not general matrix multipication

i typed special characters with the compose key; cf. https://github.com/kragen/xcompose

not as easy as latex but more compatible