Dot

score(s, h) = sᵀh
Efficient directly identifies alignment.

General

score(s, h) = sᵀWₐh
Learns a mapping between spaces.

Concat

vₐᵀ tanh(Wₐ[s;h])
Multilayer Perceptron alignment.
Window (D): 2
Global attention: all source rows in H receive non-zero weight.
Local mode restricts support to a window around predicted position p_t (radius D).