tensorflow(四十)：循环神经网络RNN

一、基础模型

1、这种模型，句子长的话，权值参数多、不能记住上下文信息。

 

 2、参数共享，并增加记忆功能。

 

 3、公式化表示RNN

 二、RNN维度解析

1、如图，假设x的维度[batch, seq_len, embedding_len]是[b, 80, 100]，则在t时刻，Xt的形状是[b, 100], 因此，[b, 100] @[100, 64] + [b, 64]@[64, 64]=[b, 64]

就是有个降维过程，100的嵌入维度，降到了我们预设的64维。X @ Wxh + h @ Whh

 

 2、如图。我们预设的隐层3维，输入形状就是[b, embedding_size]，其中嵌入维度是4.kernel0是Wxh，第二个是Whh，第三个参数是偏执b

 

 3、out维度和h维度一样。xt1就是h1

 

 

 

 

三、多层RNN

 

 

 

 

 

 

 四、实战

import  os
os.environ['TF_CPP_MIN_LOG_LEVEL']='2'

import  tensorflow as tf
import  numpy as np
from    tensorflow import keras
from    tensorflow.keras import layers


tf.random.set_seed(22)
np.random.seed(22) 
assert tf.__version__.startswith('2.')

batchsz = 128

# the most frequest words
total_words = 10000
max_review_len = 80
embedding_len = 100
(x_train, y_train), (x_test, y_test) = keras.datasets.imdb.load_data(num_words=total_words)
# x_train:[b, 80]
# x_test: [b, 80]
x_train = keras.preprocessing.sequence.pad_sequences(x_train, maxlen=max_review_len)
x_test = keras.preprocessing.sequence.pad_sequences(x_test, maxlen=max_review_len)
# 其中，drop_remainder意思是将最后一个不满一个batch的句子组丢弃
db_train = tf.data.Dataset.from_tensor_slices((x_train, y_train))
db_train = db_train.shuffle(1000).batch(batchsz, drop_remainder=True)
db_test = tf.data.Dataset.from_tensor_slices((x_test, y_test))
db_test = db_test.batch(batchsz, drop_remainder=True)
print('x_train shape:', x_train.shape, tf.reduce_max(y_train), tf.reduce_min(y_train))
print('x_test shape:', x_test.shape)



class MyRNN(keras.Model):

    def __init__(self, units):
        super(MyRNN, self).__init__()

        # [b, 64]
        self.state0 = [tf.zeros([batchsz, units])]
        self.state1 = [tf.zeros([batchsz, units])]

        # transform text to embedding representation
        # [b, 80] => [b, 80, 100]
        self.embedding = layers.Embedding(total_words, embedding_len,
                                          input_length=max_review_len)

        # [b, 80, 100] , h_dim: 64
        # RNN: cell1 ,cell2, cell3
        # SimpleRNN
        self.rnn_cell0 = layers.SimpleRNNCell(units, dropout=0.5)
        self.rnn_cell1 = layers.SimpleRNNCell(units, dropout=0.5)


        # fc, [b, 80, 100] => [b, 64] => [b, 1]
        self.outlayer = layers.Dense(1)

    def call(self, inputs, training=None):
        """
        net(x) net(x, training=True) :train mode
        net(x, training=False): test
        :param inputs: [b, 80]
        :param training:
        :return:
        """
        # [b, 80]
        x = inputs
        # embedding: [b, 80] => [b, 80, 100]
        x = self.embedding(x)
        # rnn cell compute
        # [b, 80, 100] => [b, 64]
        state0 = self.state0
        state1 = self.state1
        for word in tf.unstack(x, axis=1): # word: [b, 100]
            # h1 = x*wxh+h0*whh
            # out0: [b, 64]
            out0, state0 = self.rnn_cell0(word, state0, training)
            # out1: [b, 64]
            out1, state1 = self.rnn_cell1(out0, state1, training)

        # out: [b, 64] => [b, 1]
        x = self.outlayer(out1)
        # p(y is pos|x)
        prob = tf.sigmoid(x)

        return prob

def main():
    units = 64
    epochs = 4

    model = MyRNN(units)
    model.compile(optimizer = keras.optimizers.Adam(0.001),
                  loss = tf.losses.BinaryCrossentropy(),
                  metrics=['accuracy'],experimental_run_tf_function=False)
    model.fit(db_train, epochs=epochs, validation_data=db_test)

    model.evaluate(db_test)


if __name__ == '__main__':
    main()

 五、Layer

import  os
os.environ['TF_CPP_MIN_LOG_LEVEL']='2'

import  tensorflow as tf
import  numpy as np
from    tensorflow import keras
from    tensorflow.keras import layers


tf.random.set_seed(22)
np.random.seed(22) 
assert tf.__version__.startswith('2.')

batchsz = 128

# the most frequest words
total_words = 10000
max_review_len = 80
embedding_len = 100
(x_train, y_train), (x_test, y_test) = keras.datasets.imdb.load_data(num_words=total_words)
# x_train:[b, 80]
# x_test: [b, 80]
x_train = keras.preprocessing.sequence.pad_sequences(x_train, maxlen=max_review_len)
x_test = keras.preprocessing.sequence.pad_sequences(x_test, maxlen=max_review_len)

db_train = tf.data.Dataset.from_tensor_slices((x_train, y_train))
db_train = db_train.shuffle(1000).batch(batchsz, drop_remainder=True)
db_test = tf.data.Dataset.from_tensor_slices((x_test, y_test))
db_test = db_test.batch(batchsz, drop_remainder=True)
print('x_train shape:', x_train.shape, tf.reduce_max(y_train), tf.reduce_min(y_train))
print('x_test shape:', x_test.shape)



class MyRNN(keras.Model):

    def __init__(self, units):
        super(MyRNN, self).__init__()


        # transform text to embedding representation
        # [b, 80] => [b, 80, 100]
        self.embedding = layers.Embedding(total_words, embedding_len,
                                          input_length=max_review_len)

        # [b, 80, 100] , h_dim: 64
        self.rnn = keras.Sequential([
            layers.SimpleRNN(units, dropout=0.5, return_sequences=True, unroll=True),
            layers.SimpleRNN(units, dropout=0.5, unroll=True)
        ])


        # fc, [b, 80, 100] => [b, 64] => [b, 1]
        self.outlayer = layers.Dense(1)

    def call(self, inputs, training=None):
        """
        net(x) net(x, training=True) :train mode
        net(x, training=False): test
        :param inputs: [b, 80]
        :param training:
        :return:
        """
        # [b, 80]
        x = inputs
        # embedding: [b, 80] => [b, 80, 100]
        x = self.embedding(x)
        # rnn cell compute
        # x: [b, 80, 100] => [b, 64]
        x = self.rnn(x,training=training)

        # out: [b, 64] => [b, 1]
        x = self.outlayer(x)
        # p(y is pos|x)
        prob = tf.sigmoid(x)

        return prob

def main():
    units = 64
    epochs = 4

    model = MyRNN(units)
    # model.build(input_shape=(4,80))
    # model.summary()
    model.compile(optimizer = keras.optimizers.Adam(0.001),
                  loss = tf.losses.BinaryCrossentropy(),
                  metrics=['accuracy'])
    model.fit(db_train, epochs=epochs, validation_data=db_test)

    model.evaluate(db_test)


if __name__ == '__main__':
    main()