ffn_layer.py

# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Implementation of fully connected network."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow as tf


class FeedForwardNetwork(tf.keras.layers.Layer):
  """Fully connected feedforward network."""

  def __init__(self, hidden_size, filter_size, relu_dropout):
    """Initialize FeedForwardNetwork.

    Args:
      hidden_size: int, output dim of hidden layer.
      filter_size: int, filter size for the inner (first) dense layer.
      relu_dropout: float, dropout rate for training.
    """
    super(FeedForwardNetwork, self).__init__()
    self.hidden_size = hidden_size
    self.filter_size = filter_size
    self.relu_dropout = relu_dropout

  def build(self, input_shape):
    self.filter_dense_layer = tf.keras.layers.Dense(
        self.filter_size,
        use_bias=True,
        activation=tf.nn.relu,
        name="filter_layer")
    self.output_dense_layer = tf.keras.layers.Dense(
        self.hidden_size, use_bias=True, name="output_layer")
    super(FeedForwardNetwork, self).build(input_shape)

  def get_config(self):
    return {
        "hidden_size": self.hidden_size,
        "filter_size": self.filter_size,
        "relu_dropout": self.relu_dropout,
    }

  def call(self, x, training):
    """Return outputs of the feedforward network.

    Args:
      x: tensor with shape [batch_size, length, hidden_size]
      training: boolean, whether in training mode or not.

    Returns:
      Output of the feedforward network.
      tensor with shape [batch_size, length, hidden_size]
    """
    # Retrieve dynamically known shapes
    batch_size = tf.shape(x)[0]
    length = tf.shape(x)[1]

    output = self.filter_dense_layer(x)
    if training:
      output = tf.nn.dropout(output, rate=self.relu_dropout)
    output = self.output_dense_layer(output)

    return output