import tensorflow as tf

    # tile x from shape (b_s * i_s) to (p_s * b_s * i_s)
    post_size = tf.shape(dropout_mask_phs[0])[0]
    x = tf.tile(tf.reshape(x, [1, tf.shape(x)[0], tf.shape(x)[1]]), [post_size, 1, 1])
    # TODO: no dropout on input
