Now is the time to update the state

Now is the time to update the state of the old cell, Ct-1 is updated to Ct. The previous steps have determined what will be done, and now it is to actually complete it. the old state is multiplied by ft and the information that are certain to be useless need to be discard.Next, the old cell information Ct-1 will be updated to the new cell information Ct. The updated rule is to forget a part of the old cell information by forgetting the door, and adding a part of the candidate cell information ̃ through the input gate to obtain the new cell information Ct. The update process is as follows[5]:Ultimately, it is necessary to decide what value to output. This output will be based on our cell state but is also a filtered version according to the input ht-1 and xt . First, a sigmoid layer is employed to determine which part of the cell state will be output. Next, we process the cell state through tanh (get a value between -1 and 1) and multiply it with the output of the sigmoid gate. In the end, we will only output the part that we determined to output. The step is as follows: