勾八头歌之RNN

一、RNN快速入门

1.学习单步的RNN：RNNCell

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# -*- coding: utf-8 -*-
import tensorflow as tf

# 参数 a 是 BasicRNNCell所含的神经元数, 参数 b 是 batch_size, 参数 c 是单个 input 的维数，shape = [ b , c ]
def creatRNNCell(a,b,c):
    # 请在此添加代码 完成本关任务
    # ********** Begin *********#
    x1=tf.placeholder(tf.float32,[b,c])

    cell=tf.nn.rnn_cell.BasicRNNCell(num_units=a)
    h0=cell.zero_state(batch_size=b,dtype=tf.float32)

    output,h1=cell.__call__(x1,h0)

    print(cell.state_size)
    print(h1)
    # ********** End **********#

2.探幽入微LSTM

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# -*- coding: utf-8 -*-
import tensorflow as tf

# 参数 a 是 BasicLSTMCell所含的神经元数, 参数 b 是 batch_size, 参数 c 是单个 input 的维数，shape = [ b , c ]
def creatLSTMCell(a,b,c):
    # 请在此添加代码 完成本关任务
    # ********** Begin *********#

    x1=tf.placeholder(tf.float32,[b,c])

    cell=tf.nn.rnn_cell.BasicLSTMCell(num_units=a)
    h0=cell.zero_state(batch_size=b,dtype=tf.float32)

    output,h1=cell.__call__(x1,h0)
    
    print(h1.h)
    print(h1.c)
    # ********** End **********#

3.进阶RNN：学习一次执行多步以及堆叠RNN

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# -*- coding: utf-8 -*-
import tensorflow as tf
import numpy as np

# 参数 a 是RNN的层数, 参数 b 是每个BasicRNNCell包含的神经元数即state_size
# 参数 c 是输入序列的批量大小即batch_size，参数 d 是时间序列的步长即time_steps，参数 e 是单个输入input的维数即input_size
def MultiRNNCell_dynamic_call(a,b,c,d,e):
    # 用tf.nn.rnn_cell MultiRNNCell创建a层RNN,并调用tf.nn.dynamic_rnn
    # 请在此添加代码 完成本关任务
    # ********** Begin *********#
    cell = tf.nn.rnn_cell.MultiRNNCell([tf.nn.rnn_cell.BasicRNNCell(num_units=b) for _ in range(a)]) # a层RNN
    inputs = tf.placeholder(np.float32, shape=(c, d, e)) # a 是 batch_size，d 是time_steps, e 是input_size
    h0=cell.zero_state(batch_size=c,dtype=tf.float32)
    output, h1 = tf.nn.dynamic_rnn(cell, inputs, initial_state=h0)
    print(output)
    # ********** End **********#

二、RNN循环神经网络

1.Attention注意力机制（A ABC B C A）

2.Seq2Seq

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import numpy as np
import torch
import torch.nn as nn
import torch.optim as optim
from torch.autograd import Variable

dtype = torch.FloatTensor
char_list = [c for c in 'SEPabcdefghijklmnopqrstuvwxyz']
char_dic = {n: i for i, n in enumerate(char_list)}
seq_data = [['man', 'women'], ['black', 'white'], ['king', 'queen'], ['girl', 'boy'], ['up', 'down'], ['high', 'low']]
seq_len = 8
n_hidden = 128
n_class = len(char_list)
batch_size = len(seq_data)

##########Begin##########
#对数据进行编码部分
##########End##########
def make_batch(seq_data):
    batch_size = len(seq_data)
    input_batch, output_batch, target_batch = [], [], []
    for seq in seq_data:
        for i in range(2):
            seq[i] += 'P' * (seq_len - len(seq[i]))
        input = [char_dic[n] for n in seq[0]]
        output = [char_dic[n] for n in ('S' + seq[1])]
        target = [char_dic[n] for n in (seq[1] + 'E')]
        input_batch.append(np.eye(n_class)[input])
        output_batch.append(np.eye(n_class)[output])
        target_batch.append(target)
    return Variable(torch.Tensor(input_batch)), Variable(torch.Tensor(output_batch)), Variable(torch.LongTensor(target_batch))


##########Begin##########
#模型类定义
input_batch, output_batch, target_batch = make_batch(seq_data)
class Seq2Seq(nn.Module):
    def __init__(self):
        super(Seq2Seq, self).__init__()
        self.encoder = nn.RNN(input_size=n_class, hidden_size=n_hidden)
        self.decoder = nn.RNN(input_size=n_class, hidden_size=n_hidden)
        self.fc = nn.Linear(n_hidden, n_class)
    def forward(self, enc_input, enc_hidden, dec_input):
        enc_input = enc_input.transpose(0, 1)
        dec_input = dec_input.transpose(0, 1)
        _, h_states = self.encoder(enc_input, enc_hidden)
        outputs, _ = self.decoder(dec_input, h_states)
        outputs = self.fc(outputs)
        return outputs
##########End##########

model = Seq2Seq()
criterion = nn.CrossEntropyLoss()
optimizer = torch.optim.Adam(model.parameters(), lr=0.001)

##########Begin##########
#模型训练过程
for epoch in range(5001):
    hidden = Variable(torch.zeros(1, batch_size, n_hidden))
    optimizer.zero_grad()
    outputs = model(input_batch, hidden, output_batch)
    outputs = outputs.transpose(0, 1)
    loss = 0
    for i in range(batch_size):
        loss += criterion(outputs[i], target_batch[i])
    loss.backward()
    optimizer.step()
##########End##########


##########Begin##########
#模型验证过程函数
def translated(word):
    input_batch, output_batch, _ = make_batch([[word, 'P' * len(word)]])
    hidden = Variable(torch.zeros(1, 1, n_hidden))
    outputs = model(input_batch, hidden, output_batch)
    predict = outputs.data.max(2, keepdim=True)[1]
    decode = [char_list[i] for i in predict]
    end = decode.index('P')
    translated = ''.join(decode[:end])
    print(translated)
##########End##########

translated('highh')
translated('kingh')

三、RNN和LSTM

1.循环神经网络简介

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import torch

def rnn(input,state,params):
    """
    循环神经网络的前向传播
    :param input: 输入，形状为 [ batch_size,num_inputs ]
    :param state: 上一时刻循环神经网络的状态，形状为 [ batch_size,num_hiddens ]
    :param params: 循环神经网络的所使用的权重以及偏置
    :return: 输出结果和此时刻网络的状态
    """
    W_xh,W_hh,b_h,W_hq,b_q = params
    """
    W_xh : 输入层到隐藏层的权重
    W_hh : 上一时刻状态隐藏层到当前时刻的权重
    b_h : 隐藏层偏置
    W_hq : 隐藏层到输出层的权重
    b_q : 输出层偏置
    """
    H = state
    # 输入层到隐藏层
    H = torch.matmul(input, W_xh) + torch.matmul(H, W_hh) + b_h
    H = torch.tanh(H)
    # 隐藏层到输出层
    Y = torch.matmul(H, W_hq) + b_q
    return Y,H

def init_rnn_state(num_inputs,num_hiddens):
    """
    循环神经网络的初始状态的初始化
    :param num_inputs: 输入层中神经元的个数
    :param num_hiddens: 隐藏层中神经元的个数
    :return: 循环神经网络初始状态
    """
    init_state = torch.zeros((num_inputs,num_hiddens),dtype=torch.float32)
    return init_state

2.长短时记忆网络

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import torch

def lstm(X,state,params):
    """
    LSTM
    :param X: 输入
    :param state: 上一时刻的单元状态和输出
    :param params: LSTM 中所有的权值矩阵以及偏置
    :return: 当前时刻的单元状态和输出
    """
    W_xi, W_hi, b_i, W_xf, W_hf, b_f, W_xo, W_ho, b_o, W_xc, W_hc, b_c, W_hq, b_q = params
    """
    W_xi,W_hi,b_i : 输入门中计算i的权值矩阵和偏置
    W_xf,W_hf,b_f : 遗忘门的权值矩阵和偏置
    W_xo,W_ho,b_o : 输出门的权值矩阵和偏置
    W_xc,W_hc,b_c : 输入门中计算c_tilde的权值矩阵和偏置
    W_hq,b_q : 输出层的权值矩阵和偏置
    """
    #上一时刻的输出 H 和 单元状态 C。
    (H,C) = state
    # 遗忘门
    F = torch.matmul(X, W_xf) + torch.matmul(H, W_hf) + b_f
    F = torch.sigmoid(F)
    # 输入门
    I = torch.sigmoid(torch.matmul(X,W_xi)+torch.matmul(H,W_hi) + b_i)
    C_tilde = torch.tanh(torch.matmul(X, W_xc) + torch.matmul(H, W_hc) + b_c)
    C = F * C + I * C_tilde
    # 输出门
    O = torch.sigmoid(torch.matmul(X,W_xo)+torch.matmul(H,W_ho) + b_o)
    H = O * C.tanh()
    # 输出层
    Y = torch.matmul(H,W_hq) + b_q
    return Y,(H,C)