Gated Recurrent Update Cell

The gated recurrent update Closed GRU in the following cell is an attempt at simplifying the Long Short-Term Memory Cell. It is visualized schematically in Fig. 23.

Like the basic RNN cell, the GRU cell uses only one state h instead of the two states c and h used by an LSTM cell. Furthermore, instead of using separate input and forget gates, the GRU cell combines them in an update gate u. It also uses clever ways to combine the layer results to use fewer element-wise operations.

Fig. 23: Schematic layout of one GRU cell. Other than the basic or LSTM cells, the GRU cell makes use of additional operations to combine results of its inner layers. simply combines its inputs by taking their element-wise sum, forwards the element-wise operation 1 − x for input x.