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引言

随着全球化的深入，翻译需求日益增长。传统的人工翻译方式虽然质量高，但效率低，成本高。机器翻译的出现，为解决这一问题提供了可能。英译中机器翻译任务是机器翻译领域的一个重要分支，旨在将英文文本自动翻译成中文。本博客以《PyTorch自然语言处理入门与实战》第九章的Seq2seq模型处理英译中翻译任务作为基础，附上模型预测模块。

模型的训练及验证模块的详细解析见PyTorch实战：基于Seq2seq模型处理机器翻译任务(模型训练及验证)

数据预处理

加载字典对象en2id和zh2id

在预测阶段中，需要加载模型训练及验证阶段保存的字典对象en2id和zh2id。

代码如下：

import picklewith open("en2id.pkl", 'rb') as f:en2id = pickle.load(f)
with open("zh2id.pkl", 'rb') as f:zh2id = pickle.load(f)

文本分词

在对输入文本进行预测时，需要先将文本进行分词操作。参考代码如下：

def extract_words(sentence):  """  从给定的英文句子中提取单词，并去除单词后的标点符号。  Args:  sentence (str): 要提取单词的英文句子。  Returns:  List[str]: 提取并处理后的单词列表。  """  en_words = []  for w in sentence.split(' '):  # 将英文句子按空格分词  w = w.replace('.', '').replace(',', '')  # 去除跟单词连着的标点符号  w = w.lower()  # 统一单词大小写  if w:  en_words.append(w)  return en_words  # 测试函数  
sentence = 'I am Dave Gallo.'  
print(extract_words(sentence))

运行结果：

加载训练好的Seq2Seq模型

代码如下：

import torch
import torch.nn as nnclass Encoder(nn.Module):def __init__(self, input_dim, emb_dim, hid_dim, n_layers, dropout):super().__init__()self.hid_dim = hid_dimself.n_layers = n_layersself.embedding = nn.Embedding(input_dim, emb_dim)  # 词嵌入self.rnn = nn.LSTM(emb_dim, hid_dim, n_layers, dropout=dropout)self.dropout = nn.Dropout(dropout)def forward(self, src):# src = (src len, batch size)embedded = self.dropout(self.embedding(src))# embedded = (src len, batch size, emb dim)outputs, (hidden, cell) = self.rnn(embedded)# outputs = (src len, batch size, hid dim * n directions)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# rnn的输出总是来自顶部的隐藏层return hidden, cellclass Decoder(nn.Module):def __init__(self, output_dim, emb_dim, hid_dim, n_layers, dropout):super().__init__()self.output_dim = output_dimself.hid_dim = hid_dimself.n_layers = n_layersself.embedding = nn.Embedding(output_dim, emb_dim)self.rnn = nn.LSTM(emb_dim, hid_dim, n_layers, dropout=dropout)self.fc_out = nn.Linear(hid_dim, output_dim)self.dropout = nn.Dropout(dropout)def forward(self, input, hidden, cell):# 各输入的形状# input = (batch size)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# LSTM是单向的  ==> n directions == 1# hidden = (n layers, batch size, hid dim)# cell = (n layers, batch size, hid dim)input = input.unsqueeze(0)  # (batch size)  --> [1, batch size)embedded = self.dropout(self.embedding(input))  # (1, batch size, emb dim)output, (hidden, cell) = self.rnn(embedded, (hidden, cell))# LSTM理论上的输出形状# output = (seq len, batch size, hid dim * n directions)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# 解码器中的序列长度 seq len == 1# 解码器的LSTM是单向的 n directions == 1 则实际上# output = (1, batch size, hid dim)# hidden = (n layers, batch size, hid dim)# cell = (n layers, batch size, hid dim)prediction = self.fc_out(output.squeeze(0))# prediction = (batch size, output dim)return prediction, hidden, cellclass Seq2Seq(nn.Module):def __init__(self, input_word_count, output_word_count, encode_dim, decode_dim, hidden_dim, n_layers,encode_dropout, decode_dropout, device):""":param input_word_count:    英文词表的长度     34737:param output_word_count:   中文词表的长度     4015:param encode_dim:          编码器的词嵌入维度:param decode_dim:          解码器的词嵌入维度:param hidden_dim:          LSTM的隐藏层维度:param n_layers:            采用n层LSTM:param encode_dropout:      编码器的dropout概率:param decode_dropout:      编码器的dropout概率:param device:              cuda / cpu"""super().__init__()self.encoder = Encoder(input_word_count, encode_dim, hidden_dim, n_layers, encode_dropout)self.decoder = Decoder(output_word_count, decode_dim, hidden_dim, n_layers, decode_dropout)self.device = devicedef forward(self, src):# src = (src len, batch size)# 编码器的隐藏层输出将作为解码器的第一个隐藏层输入hidden, cell = self.encoder(src)# 解码器的第一个输入应该是起始标识符<sos>input = src[0, :]  # 取trg的第“0”行所有列  “0”指的是索引pred = [0] # 预测的第一个输出应该是起始标识符top1 = 0while top1 != 1 and len(pred) < 100:# 解码器的输入包括：起始标识符的词嵌入input; 编码器输出的 hidden and cell states# 解码器的输出包括：输出张量(predictions) and new hidden and cell statesoutput, hidden, cell = self.decoder(input, hidden, cell)top1 = output.argmax(dim=1)  # (batch size, )pred.append(top1.item())input = top1return preddevice = torch.device('cuda') if torch.cuda.is_available() else torch.device('cpu')  # GPU可用 用GPU
# Seq2Seq模型实例化
source_word_count = 34737  # 英文词表的长度     34737
target_word_count = 4015  # 中文词表的长度     4015
encode_dim = 256  # 编码器的词嵌入维度
decode_dim = 256  # 解码器的词嵌入维度
hidden_dim = 512  # LSTM的隐藏层维度
n_layers = 2  # 采用n层LSTM
encode_dropout = 0.5  # 编码器的dropout概率
decode_dropout = 0.5  # 编码器的dropout概率
model = Seq2Seq(source_word_count, target_word_count, encode_dim, decode_dim, hidden_dim, n_layers, encode_dropout,decode_dropout, device).to(device)# 加载训练好的模型
model.load_state_dict(torch.load("best_model.pth"))
model.eval()

模型预测完整代码

提示：预测代码是我们基于训练及验证代码进行改造的，不一定完全正确，可以参考后自行修改~

import torch
import torch.nn as nn
import pickleclass Encoder(nn.Module):def __init__(self, input_dim, emb_dim, hid_dim, n_layers, dropout):super().__init__()self.hid_dim = hid_dimself.n_layers = n_layersself.embedding = nn.Embedding(input_dim, emb_dim)  # 词嵌入self.rnn = nn.LSTM(emb_dim, hid_dim, n_layers, dropout=dropout)self.dropout = nn.Dropout(dropout)def forward(self, src):# src = (src len, batch size)embedded = self.dropout(self.embedding(src))# embedded = (src len, batch size, emb dim)outputs, (hidden, cell) = self.rnn(embedded)# outputs = (src len, batch size, hid dim * n directions)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# rnn的输出总是来自顶部的隐藏层return hidden, cellclass Decoder(nn.Module):def __init__(self, output_dim, emb_dim, hid_dim, n_layers, dropout):super().__init__()self.output_dim = output_dimself.hid_dim = hid_dimself.n_layers = n_layersself.embedding = nn.Embedding(output_dim, emb_dim)self.rnn = nn.LSTM(emb_dim, hid_dim, n_layers, dropout=dropout)self.fc_out = nn.Linear(hid_dim, output_dim)self.dropout = nn.Dropout(dropout)def forward(self, input, hidden, cell):# 各输入的形状# input = (batch size)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# LSTM是单向的  ==> n directions == 1# hidden = (n layers, batch size, hid dim)# cell = (n layers, batch size, hid dim)input = input.unsqueeze(0)  # (batch size)  --> [1, batch size)embedded = self.dropout(self.embedding(input))  # (1, batch size, emb dim)output, (hidden, cell) = self.rnn(embedded, (hidden, cell))# LSTM理论上的输出形状# output = (seq len, batch size, hid dim * n directions)# hidden = (n layers * n directions, batch size, hid dim)# cell = (n layers * n directions, batch size, hid dim)# 解码器中的序列长度 seq len == 1# 解码器的LSTM是单向的 n directions == 1 则实际上# output = (1, batch size, hid dim)# hidden = (n layers, batch size, hid dim)# cell = (n layers, batch size, hid dim)prediction = self.fc_out(output.squeeze(0))# prediction = (batch size, output dim)return prediction, hidden, cellclass Seq2Seq(nn.Module):def __init__(self, input_word_count, output_word_count, encode_dim, decode_dim, hidden_dim, n_layers,encode_dropout, decode_dropout, device):""":param input_word_count:    英文词表的长度     34737:param output_word_count:   中文词表的长度     4015:param encode_dim:          编码器的词嵌入维度:param decode_dim:          解码器的词嵌入维度:param hidden_dim:          LSTM的隐藏层维度:param n_layers:            采用n层LSTM:param encode_dropout:      编码器的dropout概率:param decode_dropout:      编码器的dropout概率:param device:              cuda / cpu"""super().__init__()self.encoder = Encoder(input_word_count, encode_dim, hidden_dim, n_layers, encode_dropout)self.decoder = Decoder(output_word_count, decode_dim, hidden_dim, n_layers, decode_dropout)self.device = devicedef forward(self, src):# src = (src len, batch size)# 编码器的隐藏层输出将作为解码器的第一个隐藏层输入hidden, cell = self.encoder(src)# 解码器的第一个输入应该是起始标识符<sos>input = src[0, :]  # 取trg的第“0”行所有列  “0”指的是索引pred = [0] # 预测的第一个输出应该是起始标识符top1 = 0while top1 != 1 and len(pred) < 100:# 解码器的输入包括：起始标识符的词嵌入input; 编码器输出的 hidden and cell states# 解码器的输出包括：输出张量(predictions) and new hidden and cell statesoutput, hidden, cell = self.decoder(input, hidden, cell)top1 = output.argmax(dim=1)  # (batch size, )pred.append(top1.item())input = top1return predif __name__ == '__main__':sentence = 'I am Dave Gallo.'en_words = []for w in sentence.split(' '):  # 英文内容按照空格字符进行分词# 按照空格进行分词后，某些单词后面会跟着标点符号 "." 和 “,”w = w.replace('.', '').replace(',', '')  # 去掉跟单词连着的标点符号w = w.lower()  # 统一单词大小写if w:en_words.append(w)print(en_words)with open("en2id.pkl", 'rb') as f:en2id = pickle.load(f)with open("zh2id.pkl", 'rb') as f:zh2id = pickle.load(f)device = torch.device('cuda') if torch.cuda.is_available() else torch.device('cpu')  # GPU可用 用GPU# Seq2Seq模型实例化source_word_count = 34737  # 英文词表的长度     34737target_word_count = 4015  # 中文词表的长度     4015encode_dim = 256  # 编码器的词嵌入维度decode_dim = 256  # 解码器的词嵌入维度hidden_dim = 512  # LSTM的隐藏层维度n_layers = 2  # 采用n层LSTMencode_dropout = 0.5  # 编码器的dropout概率decode_dropout = 0.5  # 编码器的dropout概率model = Seq2Seq(source_word_count, target_word_count, encode_dim, decode_dim, hidden_dim, n_layers, encode_dropout,decode_dropout, device).to(device)model.load_state_dict(torch.load("best_model.pth"))model.eval()src = [0] # 0 --> 起始标识符的编码for i in range(len(en_words)):src.append(en2id[en_words[i]])src = src + [1] # 1 --> 终止标识符的编码text_input = torch.LongTensor(src)text_input = text_input.unsqueeze(-1).to(device)text_output = model(text_input)print(text_output)id2zh = dict()for k, v in zh2id.items():id2zh[v] = ktext_output = [id2zh[index] for index in text_output]text_output = " ".join(text_output)print(text_output)

结束语

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