#update-gate

Question 1: Single choice

A GRU computes $\tilde{\mathbf{H}}_s = \tanh(\mathbf{X}_s\mathbf{W}_\textrm{xh} + (\mathbf{R}_s \odot \mathbf{H}_{s-1})\mathbf{W}_\textrm{hh} + \mathbf{b}_\textrm{h})$ and $\mathbf{H}_s = \mathbf{Z}_s \odot \mathbf{H}_{s-1} + (1 - \mathbf{Z}_s) \odot \tilde{\mathbf{H}}_s$ . You want its output at step $t$ to depend only on the input $\mathbf{X}_{t'}$ at an earlier step $t' < t$ . Which gate values achieve this?

At $t^\prime$ : $\mathbf{R} = 0$ , $\mathbf{Z} = 0$ ; at every step after $t^\prime$ up to $t$ : $\mathbf{Z} = 1$ 1
At $t^\prime$ : $\mathbf{R} = 1$ , $\mathbf{Z} = 1$ ; at every step after $t^\prime$ up to $t$ : $\mathbf{Z} = 0$ 2
At $t^\prime$ : $\mathbf{R} = 0$ , $\mathbf{Z} = 1$ ; at every step after $t^\prime$ up to $t$ : $\mathbf{R} = 0$ 3
At $t^\prime$ : $\mathbf{R} = 0$ , $\mathbf{Z} = 0$ ; at every step after $t^\prime$ up to $t$ : $\mathbf{R} = 0$ , $\mathbf{Z} = 0$ 4

Timed test