custom_recurrents.py 文件源码

def step(self, x, states):

        ytm, stm = states

        # repeat the hidden state to the length of the sequence
        _stm = K.repeat(stm, self.timesteps)

        # now multiplty the weight matrix with the repeated hidden state
        _Wxstm = K.dot(_stm, self.W_a)

        # calculate the attention probabilities
        # this relates how much other timesteps contributed to this one.
        et = K.dot(activations.tanh(_Wxstm + self._uxpb),
                   K.expand_dims(self.V_a))
        at = K.exp(et)
        at_sum = K.sum(at, axis=1)
        at_sum_repeated = K.repeat(at_sum, self.timesteps)
        at /= at_sum_repeated  # vector of size (batchsize, timesteps, 1)

        # calculate the context vector
        context = K.squeeze(K.batch_dot(at, self.x_seq, axes=1), axis=1)
        # ~~~> calculate new hidden state
        # first calculate the "r" gate:

        rt = activations.sigmoid(
            K.dot(ytm, self.W_r)
            + K.dot(stm, self.U_r)
            + K.dot(context, self.C_r)
            + self.b_r)

        # now calculate the "z" gate
        zt = activations.sigmoid(
            K.dot(ytm, self.W_z)
            + K.dot(stm, self.U_z)
            + K.dot(context, self.C_z)
            + self.b_z)

        # calculate the proposal hidden state:
        s_tp = activations.tanh(
            K.dot(ytm, self.W_p)
            + K.dot((rt * stm), self.U_p)
            + K.dot(context, self.C_p)
            + self.b_p)

        # new hidden state:
        st = (1-zt)*stm + zt * s_tp

        yt = activations.softmax(
            K.dot(ytm, self.W_o)
            + K.dot(stm, self.U_o)
            + K.dot(context, self.C_o)
            + self.b_o)

        if self.return_probabilities:
            return at, [yt, st]
        else:
            return yt, [yt, st]