Sequence Model-week1编程题2-Character level language model【RNN生成恐龙名 LSTM生成莎士比亚风格文字】

Character level language model - Dinosaurus land

为了构建字符级语言模型来生成新的名称，你的模型将学习不同的名字，并随机生成新的名字。

任务清单：

• 如何存储文本数据，以便使用RNN进行处理。

• 如何合成数据，通过采样在每个time step预测，并通过下一个RNN-cell unit。

• 如何构建字符级文本，生成循环神经网络(RNN)。

• 为什么梯度修剪(clipping the gradients)很重要?

import numpy as np
import random
import time
import cllm_utils

1. 问题描述(Problem Statement)

1.1 数据集与预处理(Dataset and Preprocessing)

data = open('datasets/dinos.txt', 'r').read()
# 单词全转换为小写
data= data.lower()
# 转化为无序且不重复的元素列表
chars = list(set(data))
print(chars)
data_size, vocab_size = len(data), len(chars)
print('There are %d total characters and %d unique characters in your data.' % (data_size, vocab_size))

['i', '\n', 'd', 'e', 'v', 'f', 'l', 'g', 'u', 'm', 'y', 'q', 'w', 's', 'k', 't', 'a', 'h', 'o', 'n', 'r', 'x', 'j', 'z', 'c', 'b', 'p']

There are 19909 total characters and 27 unique characters in your data.

这些字符是a-z（26个英文字符）加上“\n”（换行字符），在这里换行字符起到了在视频中类似的EOS（句子结尾）的作用， 这里表示了名字的结束而不是句子的结尾。下面我们将创建一个字典，每个字符映射到0-26的索引，然后再创建一个字典，该字典每个索引映射相应的字符，它会帮助我们找出softmax层的概率分布输出中的字符。下面创建 char_to_ix 和 ix_to_char 字典。

char_to_ix = { ch:i for i,ch in enumerate(sorted(chars)) }
ix_to_char = { i:ch for i,ch in enumerate(sorted(chars)) }
print(ix_to_char)

{0: '\n', 1: 'a', 2: 'b', 3: 'c', 4: 'd', 5: 'e', 6: 'f', 7: 'g', 8: 'h', 9: 'i', 10: 'j', 11: 'k', 12: 'l', 13: 'm', 14: 'n', 15: 'o', 16: 'p', 17: 'q', 18: 'r', 19: 's', 20: 't', 21: 'u', 22: 'v', 23: 'w', 24: 'x', 25: 'y', 26: 'z'}

1.2 模型概述(Overview of the model)

模型结构如下：

• 初始化参数

• 运行optimization循环：

  • 前向传播 计算 loss function

  • 反向传播 计算关于 loss function 的梯度

  • 修建梯度(Clip the gradients) 避免梯度爆炸

  • 用梯度下降更新规则 更新参数

• 返回学习好的参数

Figure 1: Recurrent Neural Network.

在每个时间步, RNN 会预测给定字符的下一个字符是什么。数据集 \(X = (x^{\langle 1 \rangle}, x^{\langle 2 \rangle}, ..., x^{\langle T_x \rangle})\) 在训练集是字符的列表, 同时 \(Y = (y^{\langle 1 \rangle}, y^{\langle 2 \rangle}, ..., y^{\langle T_x \rangle})\) 在每个time-step \(t\) 也是如此。 我们有：\(x^{\langle t+1 \rangle} = y^{\langle t \rangle}\).

2. 构建模型中的模块(Building blocks of the model)

构建模型两个重要的模块：

• 梯度修建(Gradient clipping)：避免梯度爆炸(exploding gradients)

• 取样(Sampling)：一种用来生成字符的技术

2.1 梯度修剪(Clipping the gradients in the optimization loop)

在这里，我们将实现将调用的clip函数在优化循环中。整个循环结构包含：前向传播，计算cost，反向传播和参数更新。在更新参数之前，我们需要在需要时执行梯度修剪，以确保不会梯度爆炸。

接下来我们将实现一个修剪函数，该函数：输入一个梯度字典，输出一个已经修剪过了的梯度。有许多不同的方法进行梯度修剪。我们将使用 element-wise clipping procedure，梯度向量的每一个元素都被限制在[-N, N]的范围。例，有一个maxValue（比如10），如果梯度的任何值大于10，那么它将被设置为10，那么梯度的任何值小于-10，如果它在-10-10之间，则不变。

Figure 2: 在网络进入轻微的 "exploding gradient"问题，使用无梯度修剪 和 梯度修剪的可视化图。

Exercise: 实现下面的函数，返回一个修剪过后的梯度字典 gradients；函数接受 maximum threshold，并返回修剪后的梯度。

### GRADED FUNCTION: clip
def clip(gradients, maxValue):
    '''
    Clips the gradients' values between minimum and maximum.
    Arguments:
    gradients -- a dictionary containing the gradients "dWaa", "dWax", "dWya", "db", "dby"
    maxValue -- everything above this number is set to this number, and everything less than -maxValue is set to -maxValue
    Returns:
    gradients -- a dictionary with the clipped gradients.
    '''
    dWaa, dWax, dWya, db, dby = gradients['dWaa'], gradients['dWax'], gradients['dWya'], gradients['db'], gradients['dby']
    ### START CODE HERE ###
    # clip to mitigate exploding gradients, loop over [dWax, dWaa, dWya, db, dby]. (≈2 lines)
    for gradient in [dWax, dWaa, dWya, db, dby]:
        gradient.clip(-maxValue, maxValue, out=gradient)
    ### END CODE HERE ###
    gradients = {"dWaa": dWaa, "dWax": dWax, "dWya": dWya, "db": db, "dby": dby}
    return gradients

测试：

np.random.seed(3)
dWax = np.random.randn(5,3)*10
dWaa = np.random.randn(5,5)*10
dWya = np.random.randn(2,5)*10
db = np.random.randn(5,1)*10
dby = np.random.randn(2,1)*10
gradients = {"dWax": dWax, "dWaa": dWaa, "dWya": dWya, "db": db, "dby": dby}
gradients = clip(gradients, 10)
print("gradients[\"dWaa\"][1][2] =", gradients["dWaa"][1][2])
print("gradients[\"dWax\"][3][1] =", gradients["dWax"][3][1])
print("gradients[\"dWya\"][1][2] =", gradients["dWya"][1][2])
print("gradients[\"db\"][4] =", gradients["db"][4])
print("gradients[\"dby\"][1] =", gradients["dby"][1])

测试：

np.random.seed(3)
dWax = np.random.randn(5,3)*10
dWaa = np.random.randn(5,5)*10
dWya = np.random.randn(2,5)*10
db = np.random.randn(5,1)*10
dby = np.random.randn(2,1)*10
gradients = {"dWax": dWax, "dWaa": dWaa, "dWya": dWya, "db": db, "dby": dby}
gradients = clip(gradients, 10)
print("gradients[\"dWaa\"][1][2] =", gradients["dWaa"][1][2])
print("gradients[\"dWax\"][3][1] =", gradients["dWax"][3][1])
print("gradients[\"dWya\"][1][2] =", gradients["dWya"][1][2])
print("gradients[\"db\"][4] =", gradients["db"][4])
print("gradients[\"dby\"][1] =", gradients["dby"][1])

gradients["dWaa"][1][2] = 10.0

gradients["dWax"][3][1] = -10.0

gradients["dWya"][1][2] = 0.2971381536101662

gradients["db"][4] = [10.]

gradients["dby"][1] = [8.45833407]

2.2 采样(Sampling)

假设你的模型已经训练好，你将生成新的文本（字符），生成的过程如下图：

Figure 3: 我们假设模型已经训练过了。我们在第一步传入 \(x^{\langle 1\rangle} = \vec{0}\)，然后让网络一次对一个字符进行采样。

Exercise: 实现 sample 函数. 有4个步骤：

• Step 1： 网络的第一个输入是 "dummy" input \(x^{\langle 1 \rangle} = \vec{0}\) (零向量)。 这是在生成字符之前的默认输入。 同时设置 \(a^{\langle 0 \rangle} = \vec{0}\)

• Step 2： 运行一次 forward propagation，然后得到 \(a^{\langle 1 \rangle}\) and \(\hat{y}^{\langle 1 \rangle}\)。公式如下:

\[a^{\langle t+1 \rangle} = \tanh(W_{ax} x^{\langle t \rangle } + W_{aa} a^{\langle t \rangle } + b)\tag{1}
\]

\[z^{\langle t + 1 \rangle } = W_{ya} a^{\langle t + 1 \rangle } + b_y \tag{2}
\]

\[\hat{y}^{\langle t+1 \rangle } = softmax(z^{\langle t + 1 \rangle })\tag{3}
\]

注意 \(\hat{y}^{\langle t+1 \rangle }\) 是一个 (softmax) 概率向量(probability vector) (its entries are between 0 and 1 and sum to 1)；\(\hat{y}^{\langle t+1 \rangle}_i\) 表示索引“i”的字符是下一个字符的概率。

• Step 3： 采样(sampling)： 根据\(\hat{y}^{\langle t+1 \rangle }\) 指定的概率分布选择下一个字符的索引，假如 \(\hat{y}^{\langle t+1 \rangle }_i = 0.16\), 那么选择索引 "i" 的概率是 16%，为了实现它，你可以使用 np.random.choice.

Here is an example of how to use np.random.choice()：

np.random.seed(0)
p = np.array([0.1, 0.0, 0.7, 0.2])
index = np.random.choice([0, 1, 2, 3], p = p.ravel())

这意味着你将根据分布选择索引：

\(P(index = 0) = 0.1, P(index = 1) = 0.0, P(index = 2) = 0.7, P(index = 3) = 0.2\).

• Step 4： 在 sample() 中实现的最后一步是用 \(x^{\langle t + 1 \rangle }\) 的值覆盖变量 x(当前存储\(x^{\langle t \rangle }\))。

  • 我们将创建一个与我们 所选择的字符(对应索引idx=1)相对应的one-hot向量([0,1,0,...]) 来表示 \(x^{\langle t + 1 \rangle }\) 作为预测。

  • 然后在步骤1中前向传播 \(x^{\langle t + 1 \rangle }\) ，并不断重复这个过程 直到得到一个 "\n" 字符， 表明已经到达恐龙名称的末尾。

# GRADED FUNCTION: sample
def sample(parameters, char_to_ix, seed):
    """
    Sample a sequence of characters according to a sequence of probability distributions output of the RNN
    Arguments:
    parameters -- python dictionary containing the parameters Waa, Wax, Wya, by, and b.
    char_to_ix -- python dictionary mapping each character to an index.
    seed -- used for grading purposes. Do not worry about it.
    Returns:
    indices -- a list of length n containing the indices of the sampled characters.
    """
    # Retrieve parameters and relevant shapes from "parameters" dictionary
    Waa, Wax, Wya, by, b = parameters['Waa'], parameters['Wax'], parameters['Wya'], parameters['by'], parameters['b']
#     print(Wya.shape, by.shape)
    vocab_size = by.shape[0]
    n_a = Waa.shape[1]
    ### START CODE HERE ###
    # Step 1: Create the one-hot vector x for the first character (initializing the sequence generation). (≈1 line)
    x = np.zeros((vocab_size, 1))
    # Step 1': Initialize a_prev as zeros (≈1 line)
    a_prev = np.zeros((n_a, 1))
    # 创建索引的空列表，这是包含要生成的字符的索引的列表。
    indices = []
    # idx是检测换行符的标志，将其初始化为-1。
    idx = -1 
    # Loop over time-steps t. At each time-step, sample(抽取) a character from a probability distribution(概率分布)
    # append its index to "indices"(将其索引附加到“indices”上). We'll stop if we reach 50 characters
    #  (which should be very unlikely with a well trained model),
    # which helps debugging and prevents entering an infinite loop.(这有助于调试,并防止进入无限循环)
    counter = 0
    newline_character = char_to_ix['\n']
    while (idx != newline_character and counter != 50):
        # Step 2: Forward propagate x using the equations (1), (2) and (3)
        a = np.tanh(np.dot(Wax, x) + np.dot(Waa, a_prev) + b)
        z = np.dot(Wya, a) + by
        y = softmax(z)   
        # for grading purposes
        np.random.seed(counter+seed)
        # Step 3: Sample the index of a character within the vocabulary from the probability distribution y
        idx = np.random.choice(list(range(vocab_size)), p = y.ravel())   # y是概率, idx是概率最大的元素
        # Append the index to "indices"
        indices.append(idx)
        # Step 4: Overwrite the input character as the one corresponding to the sampled index.
        x = np.zeros((vocab_size, 1))
        x[idx] = 1
        # Update "a_prev" to be "a"
        a_prev = a
        # for grading purposes
        seed += 1
        counter +=1
    ### END CODE HERE ###
    if (counter == 50):
        indices.append(char_to_ix['\n'])
    return indices

测试：

np.random.seed(2)
_, n_a = 20, 100
Wax, Waa, Wya = np.random.randn(n_a, vocab_size), np.random.randn(n_a, n_a), np.random.randn(vocab_size, n_a)
b, by = np.random.randn(n_a, 1), np.random.randn(vocab_size, 1)
parameters = {"Wax": Wax, "Waa": Waa, "Wya": Wya, "b": b, "by": by}
indices = sample(parameters, char_to_ix, 0)
print("Sampling:")
print("list of sampled indices:", indices)
print("list of sampled characters:", [ix_to_char[i] for i in indices])

Sampling:

list of sampled indices: [12, 17, 24, 14, 13, 9, 10, 22, 24, 6, 13, 11, 12, 6, 21, 15, 21, 14, 3, 2, 1, 21, 18, 24, 7, 25, 6, 25, 18, 10, 16, 2, 3, 8, 15, 12, 11, 7, 1, 12, 10, 2, 7, 7, 11, 17, 24, 12, 3, 1, 0]

list of sampled characters: ['l', 'q', 'x', 'n', 'm', 'i', 'j', 'v', 'x', 'f', 'm', 'k', 'l', 'f', 'u', 'o', 'u', 'n', 'c', 'b', 'a', 'u', 'r', 'x', 'g', 'y', 'f', 'y', 'r', 'j', 'p', 'b', 'c', 'h', 'o', 'l', 'k', 'g', 'a', 'l', 'j', 'b', 'g', 'g', 'k', 'q', 'x', 'l', 'c', 'a', '\n']

3. 构建语言模型(Building the language model)

3.1 Gradient descent

在这里，我们将实现一个执行 随机梯度下降 的一个步骤的函数（带有梯度修剪）。我们将一次训练一个样本，所以优化算法将是随机梯度下降，这里是RNN的一个通用的优化循环的步骤：

• 通过RNN前向传播计算cost.
• 通过时间，反向传播计算关于参数的梯度损失.
• 梯度修剪.
• 使用梯度下降更新参数.

Exercise: Implement this optimization process (one step of stochastic gradient descent)，下为已知函数.

def rnn_forward(X, Y, a_prev, parameters):
    """ Performs the forward propagation through the RNN and computes the cross-entropy loss.
    It returns the loss' value as well as a "cache" storing values to be used in the backpropagation."""
    ....
    return loss, cache
def rnn_backward(X, Y, parameters, cache):
    """ Performs the backward propagation through time to compute the gradients of the loss with respect
    to the parameters. It returns also all the hidden states."""
    ...
    return gradients, a
def update_parameters(parameters, gradients, learning_rate):
    """ Updates parameters using the Gradient Descent Update Rule."""
    ...
    return parameters

# GRADED FUNCTION: optimize
def optimize(X, Y, a_prev, parameters, learning_rate = 0.01):
    """
    Execute one step of the optimization to train the model.
    Arguments:
    X -- list of integers, where each integer is a number that maps to a character in the vocabulary.
    Y -- 整数列表，与X完全相同，但向左移动了一个索引。
    a_prev -- previous hidden state.
    parameters -- python dictionary containing:
                        Wax -- Weight matrix multiplying the input, numpy array of shape (n_a, n_x)
                        Waa -- Weight matrix multiplying the hidden state, numpy array of shape (n_a, n_a)
                        Wya -- Weight matrix relating the hidden-state to the output, numpy array of shape (n_y, n_a)
                        b --  Bias, numpy array of shape (n_a, 1)
                        by -- Bias relating the hidden-state to the output, numpy array of shape (n_y, 1)
    learning_rate -- learning rate for the model.
    Returns:
    loss -- value of the loss function (cross-entropy)
    gradients -- python dictionary containing:
                        dWax -- Gradients of input-to-hidden weights, of shape (n_a, n_x)
                        dWaa -- Gradients of hidden-to-hidden weights, of shape (n_a, n_a)
                        dWya -- Gradients of hidden-to-output weights, of shape (n_y, n_a)
                        db -- Gradients of bias vector, of shape (n_a, 1)
                        dby -- Gradients of output bias vector, of shape (n_y, 1)
    a[len(X)-1] -- the last hidden state, of shape (n_a, 1)
    """
    ### START CODE HERE ###
    # Forward propagate through time (≈1 line)
    loss, cache = rnn_forward(X, Y, a_prev, parameters)
    # Backpropagate through time (≈1 line)
    gradients, a = rnn_backward(X, Y, parameters, cache)
    # Clip your gradients between -5 (min) and 5 (max) (≈1 line)
    gradients = clip(gradients, 5)
    # Update parameters (≈1 line)
    parameters = update_parameters(parameters, gradients, learning_rate)
    ### END CODE HERE ###
    return loss, gradients, a[len(X)-1]

测试：

np.random.seed(1)
vocab_size, n_a = 27, 100
a_prev = np.random.randn(n_a, 1)
Wax, Waa, Wya = np.random.randn(n_a, vocab_size), np.random.randn(n_a, n_a), np.random.randn(vocab_size, n_a)
b, by = np.random.randn(n_a, 1), np.random.randn(vocab_size, 1)
parameters = {"Wax": Wax, "Waa": Waa, "Wya": Wya, "b": b, "by": by}
X = [12,3,5,11,22,3]
Y = [4,14,11,22,25, 26]
loss, gradients, a_last = optimize(X, Y, a_prev, parameters, learning_rate = 0.01)
print("Loss =", loss)
print("gradients[\"dWaa\"][1][2] =", gradients["dWaa"][1][2])
print("np.argmax(gradients[\"dWax\"]) =", np.argmax(gradients["dWax"]))
print("gradients[\"dWya\"][1][2] =", gradients["dWya"][1][2])
print("gradients[\"db\"][4] =", gradients["db"][4])
print("gradients[\"dby\"][1] =", gradients["dby"][1])
print("a_last[4] =", a_last[4])

Loss = 126.503975722

gradients["dWaa"][1][2] = 0.194709315347

np.argmax(gradients["dWax"]) = 93

gradients["dWya"][1][2] = -0.007773876032

gradients["db"][4] = [-0.06809825]

gradients["dby"][1] = [ 0.01538192]

a_last[4] = [-1.]

3.2 Training the model

给定数据集 dinosaur names，我们使用数据集的每一行（一个名称）作为一个训练样本。每100步随机梯度下降，你将抽样10个随机选择的名字，看看算法是怎么做的。记住要打乱数据集，以便随机梯度下降以随机顺序访问样本。

Exercise: 实现 model().

当 examples[index] 包含一个 dinosaur name (string)，为了创建example (X, Y), 可以使用：

        index = j % len(examples)
        X = [None] + [char_to_ix[ch] for ch in examples[index]]
        Y = X[1:] + [char_to_ix["\n"]]

注意：我们使用 index= j % len(examples), 其中 j = 1....num_iterations, 为了确保 examples[index] 总是有效 (index 小于 len(examples))。

rnn_forward() 会将 X 的第一个值 None 解释为 \(x^{\langle 0 \rangle} = \vec{0}\)。 此外，为了确保 Y 等于 X ，会向左移动一步，并添加一个附加的“\n”以表示恐龙名称的结束。

# GRADED FUNCTION: model
def model(data, ix_to_char, char_to_ix, num_iterations = 35000, n_a = 50, dino_names = 7, vocab_size = 27):
    """
    Trains the model and generates dinosaur names. 
    Arguments:
    data -- text corpus
    ix_to_char -- dictionary that maps the index to a character
    char_to_ix -- dictionary that maps a character to an index
    num_iterations -- number of iterations to train the model for
    n_a -- number of units of the RNN cell
    dino_names -- number of dinosaur names you want to sample at each iteration.
    vocab_size -- number of unique characters found in the text, size of the vocabulary
    Returns:
    parameters -- learned parameters
    """
    # Retrieve n_x and n_y from vocab_size
    n_x, n_y = vocab_size, vocab_size
    # Initialize parameters
    parameters = initialize_parameters(n_a, n_x, n_y)
    # Initialize loss (this is required because we want to smooth our loss, don't worry about it)
    loss = get_initial_loss(vocab_size, dino_names)
    # Build list of all dinosaur names (training examples).
    with open("./datasets/dinos.txt") as f:
        examples = f.readlines()
    examples = [x.lower().strip() for x in examples]     # 名字列表
    # Shuffle list of all dinosaur names
    np.random.seed(0)
    np.random.shuffle(examples)
    # Initialize the hidden state of your LSTM
    a_prev = np.zeros((n_a, 1))
    # Optimization loop
    for j in range(num_iterations):
        ### START CODE HERE ###
        # Use the hint above to define one training example (X,Y) (≈ 2 lines)
        index = j % len(examples)
        X = [None] + [char_to_ix[ch] for ch in examples[index]]
        Y = X[1:] + [char_to_ix['\n']]
        # Perform one optimization step: Forward-prop -> Backward-prop -> Clip -> Update parameters
        # Choose a learning rate of 0.01
        curr_loss, gradients, a_prev = optimize(X, Y, a_prev, parameters, learning_rate = 0.01)
        ### END CODE HERE ###
        # Use a latency trick to keep the loss smooth. It happens here to accelerate the training.
        loss = smooth(loss, curr_loss)
        # Every 2000 Iteration, generate "n" characters thanks to sample() to check if the model is learning properly
        if j % 2000 == 0:
            print('Iteration: %d, Loss: %f' % (j, loss) + '\n')
            # The number of dinosaur names to print
            seed = 0
            for name in range(dino_names):
                # Sample indices and print them
                sampled_indices = sample(parameters, char_to_ix, seed)
                print_sample(sampled_indices, ix_to_char)
                seed += 1  # To get the same result for grading purposed, increment the seed by one. 
            print('\n')
    return parameters

运行全部

parameters = model(data, ix_to_char, char_to_ix)

输出：

Iteration: 0, Loss: 23.087336
Nkzxwtdmfqoeyhsqwasjkjvu
Kneb
Kzxwtdmfqoeyhsqwasjkjvu
Neb
Zxwtdmfqoeyhsqwasjkjvu
Eb
Xwtdmfqoeyhsqwasjkjvu
Iteration: 2000, Loss: 27.884160
Liusskeomnolxeros
Hmdaairus
Hytroligoraurus
Lecalosapaus
Xusicikoraurus
Abalpsamantisaurus
Tpraneronxeros
Iteration: 4000, Loss: 25.901815
Mivrosaurus
Inee
Ivtroplisaurus
Mbaaisaurus
Wusichisaurus
Cabaselachus
Toraperlethosdarenitochusthiamamumamaon
Iteration: 6000, Loss: 24.608779
Onwusceomosaurus
Lieeaerosaurus
Lxussaurus
Oma
Xusteonosaurus
Eeahosaurus
Toreonosaurus
Iteration: 8000, Loss: 24.070350
Onxusichepriuon
Kilabersaurus
Lutrodon
Omaaerosaurus
Xutrcheps
Edaksoje
Trodiktonus
Iteration: 10000, Loss: 23.844446
Onyusaurus
Klecalosaurus
Lustodon
Ola
Xusodonia
Eeaeosaurus
Troceosaurus
Iteration: 12000, Loss: 23.291971
Onyxosaurus
Kica
Lustrepiosaurus
Olaagrraiansaurus
Yuspangosaurus
Eealosaurus
Trognesaurus
Iteration: 14000, Loss: 23.382338
Meutromodromurus
Inda
Iutroinatorsaurus
Maca
Yusteratoptititan
Ca
Troclosaurus
Iteration: 16000, Loss: 23.268257
Mbutosaurus
Indaa
Iustolophulurus
Macagosaurus
Yusoclichaurus
Caahosaurus
Trodon
Iteration: 18000, Loss: 22.928870
Phytrogiaps
Mela
Mustrha
Pegamosaurus
Ytromacisaurus
Efanshie
Troma
Iteration: 20000, Loss: 23.008798
Onyusperchohychus
Lola
Lytrranfosaurus
Olaa
Ytrrcharomulus
Ehagosaurus
Trrcharonyhus
Iteration: 22000, Loss: 22.794515
Onyvus
Llecakosaurus
Mustodonosaurus
Ola
Yusodon
Eiadosaurus
Trodontorus
Iteration: 24000, Loss: 22.648635
Meutosaurus
Incaachudachus
Itntodon
Mecaessan
Yurong
Daadropachusaurus
Troenatheusaurosaurus
Iteration: 26000, Loss: 22.599152
Nixusehoenomulushapnelspanthuonathitalia
Jigaadroncansaurus
Kustodonis
Nedantrocantiteniupegyankuaeusalomarotimenmpangvin
Ytrodongoluctos
Eebdssaegoterichus
Trodolopiunsitarbilus
Iteration: 28000, Loss: 22.628455
Pnywrodilosaurus
Loca
Mustodonanethosaurus
Phabesceeatopsaurus
Ytrodonnoludosaurus
Elaishacaosaurus
Trrdilosaurus
Iteration: 30000, Loss: 22.587893
Piusosaurus
Locaadrus
Lutosaurus
Pacalosaurus
Yusochesaurus
Eg
Trraodon
Iteration: 32000, Loss: 22.314649
Nivosaurus
Jiacamisaurus
Kusplasaurus
Ncaadosaurus
Yusiandon
Eeaisilaanus
Trokalenator
Iteration: 34000, Loss: 22.445100
Mewsroengosaurus
Ilabafosaurus
Justoeomimavesaurus
Macaeosaurus
Yrosaurus
Eiaeosaurus
Trodondolus

4. 写出莎士比亚风格的文字(Writing like Shakespeare)

任务是产生莎士比亚诗歌，使用莎士比亚诗集。使用LSTM单元，我们可以学习跨越文本中许多字符的较长时间的依赖关系，例如，出现在某个序列的某个字符，会影响在该序列后面的不同字符。由于恐龙名字很短，这些长期的依赖性与恐龙名字并不那么重要。我们用Keras实现了莎士比亚诗歌生成器，我们先来加载所需的包和模型，这可能需要几分钟。

from __future__ import print_function
from keras.callbacks import LambdaCallback
from keras.models import Model, load_model, Sequential
from keras.layers import Dense, Activation, Dropout, Input, Masking
from keras.layers import LSTM
from keras.utils.data_utils import get_file
from keras.preprocessing.sequence import pad_sequences
from shakespeare_utils import *
import sys
import io

Loading text data...

Creating training set...

number of training examples: 31412

Vectorizing training set...

Loading model...

为了节省时间，我们已经为莎士比亚诗集《十四行诗》模型训练了1000代（让我们再训练一下这个模型。当它完成了一代的训练——这也需要几分钟）——你可以运行generate_output，这首诗将从你的句子开始，我们的RNN-Shakespeare将为你完成这首诗的其余部分

迭代一次：

print_callback = LambdaCallback(on_epoch_end=on_epoch_end)
model.fit(x, y, batch_size=128, epochs=1, callbacks=[print_callback])

Epoch 1/1

31412/31412 [==============================] - 27s 846us/step - loss: 2.7274

# Run this cell to try with different inputs without having to re-train the model
generate_output()

rite the beginning of your poem, the Shakespeare machine will complete it. Your input is: Forsooth this maketh no sense

Here is your poem:

Forsooth this maketh no sense.

to that i his bongy of sacu, or when thee grace.

to peirout i have sweet from thee, ald the will,

in this, as thy dealt besich whereor me hall thy dould,

and thee and creasts of the cantensed site,

my heart which that a form and ridcus forsed:

for thy coneloting thy where hors of sich,

that prow'st and thincior with with now,

as makted for thou best, and parking frank,

it place corsack thas

查看模型细节：

#------------用于绘制模型细节，可选--------------#
from IPython.display import SVG
from keras.utils.vis_utils import model_to_dot
from keras.utils import plot_model
%matplotlib inline
plot_model(model, to_file='shakespeare.png')
SVG(model_to_dot(model).create(prog='dot', format='svg'))
#------------------------------------------------#