关键词在线优化乐天seo培训中心

• 🍨 本文为🔗365天深度学习训练营 中的学习记录博客
• 🍖 原作者：K同学啊 | 接辅导、项目定制

一、我的环境

1.语言环境：Python 3.8

2.编译器：Pycharm

3.深度学习环境：

• torch==1.12.1+cu113
• torchvision==0.13.1+cu113

二、导入数据

import torch
import torch.nn as nn
import torchvision
from torchvision import transforms, datasets
import os,PIL,pathlib,warningswarnings.filterwarnings("ignore")             #忽略警告信息
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")from torchtext.datasets import AG_NEWS
train_iter = AG_NEWS(split='train')      # 加载 AG News 数据集

三、构建词典

from torchtext.data.utils import get_tokenizer
from torchtext.vocab import build_vocab_from_iteratortokenizer  = get_tokenizer('basic_english') # 返回分词器函数def yield_tokens(data_iter):for _, text in data_iter:yield tokenizer(text)vocab = build_vocab_from_iterator(yield_tokens(train_iter), specials=["<unk>"])
vocab.set_default_index(vocab["<unk>"]) # 设置默认索引，如果找不到单词，则会选择默认索引
print(vocab(['here', 'is', 'an', 'example']))

结果： [475, 21, 30, 5297]

text_pipeline  = lambda x: vocab(tokenizer(x))
label_pipeline = lambda x: int(x) - 1
print(text_pipeline('here is the an example'))
结果：[475, 21, 2, 30, 5297]

print(label_pipeline('10'))
结果：10

四、生成数据批次和迭代器

from torch.utils.data import DataLoaderdef collate_batch(batch):label_list, text_list, offsets = [], [], [0]for (_label, _text) in batch:# 标签列表label_list.append(label_pipeline(_label))# 文本列表processed_text = torch.tensor(text_pipeline(_text), dtype=torch.int64)text_list.append(processed_text)# 偏移量，即语句的总词汇量offsets.append(processed_text.size(0))label_list = torch.tensor(label_list, dtype=torch.int64)text_list  = torch.cat(text_list)offsets    = torch.tensor(offsets[:-1]).cumsum(dim=0) #返回维度dim中输入元素的累计和return label_list.to(device), text_list.to(device), offsets.to(device)# 数据加载器
dataloader = DataLoader(train_iter,batch_size=8,shuffle   =False,collate_fn=collate_batch)

五、定义模型

from torch import nnclass TextClassificationModel(nn.Module):def __init__(self, vocab_size, embed_dim, num_class):super(TextClassificationModel, self).__init__()self.embedding = nn.EmbeddingBag(vocab_size,   # 词典大小embed_dim,    # 嵌入的维度sparse=False) # self.fc = nn.Linear(embed_dim, num_class)self.init_weights()def init_weights(self):initrange = 0.5self.embedding.weight.data.uniform_(-initrange, initrange)self.fc.weight.data.uniform_(-initrange, initrange)self.fc.bias.data.zero_()def forward(self, text, offsets):embedded = self.embedding(text, offsets)return self.fc(embedded)

六、定义实例

num_class  = len(set([label for (label, text) in train_iter]))
vocab_size = len(vocab)
em_size     = 64
model      = TextClassificationModel(vocab_size, em_size, num_class).to(device)

七、定义训练函数与评估函数

import timedef train(dataloader):model.train()  # 切换为训练模式total_acc, train_loss, total_count = 0, 0, 0log_interval = 500start_time   = time.time()for idx, (label, text, offsets) in enumerate(dataloader):predicted_label = model(text, offsets)optimizer.zero_grad()                    # grad属性归零loss = criterion(predicted_label, label) # 计算网络输出和真实值之间的差距，label为真实值loss.backward()                          # 反向传播optimizer.step()  # 每一步自动更新# 记录acc与losstotal_acc   += (predicted_label.argmax(1) == label).sum().item()train_loss  += loss.item()total_count += label.size(0)if idx % log_interval == 0 and idx > 0:elapsed = time.time() - start_timeprint('| epoch {:1d} | {:4d}/{:4d} batches ''| train_acc {:4.3f} train_loss {:4.5f}'.format(epoch, idx, len(dataloader),total_acc/total_count, train_loss/total_count))total_acc, train_loss, total_count = 0, 0, 0start_time = time.time()def evaluate(dataloader):model.eval()  # 切换为测试模式total_acc, train_loss, total_count = 0, 0, 0with torch.no_grad():for idx, (label, text, offsets) in enumerate(dataloader):predicted_label = model(text, offsets)loss = criterion(predicted_label, label)  # 计算loss值# 记录测试数据total_acc   += (predicted_label.argmax(1) == label).sum().item()train_loss  += loss.item()total_count += label.size(0)return total_acc/total_count, train_loss/total_count

 结果：

| epoch 1 | 500/1782 batches| train_acc 0.901 train_loss 0.00458
| epoch 1 | 1000/1782 batches| train_acc 0.905 train_loss 0.00438
| epoch 1 | 1500/1782 batches| train_acc 0.908 train_loss 0.00437
---------------------------------------------------------------------
| epoch 1 | time:6.30s |valid_acc 0.907 | valid_loss 0.004
---------------------------------------------------------------------
| epoch 2 | 500/1782 batches| train_acc 0.917 train_loss 0.00381
| epoch 2 | 1000/1782 batches| train_acc 0.917 train_loss 0.00383
| epoch 2 | 1500/1782 batches| train_acc 0.917 train_loss 0.00386
---------------------------------------------------------------------
| epoch 2 | time:6.26s |valid_acc 0.911 | valid_loss 0.004
---------------------------------------------------------------------
| epoch 3 | 500/1782 batches| train_acc 0.929 train_loss 0.00330
| epoch 3 | 1000/1782 batches| train_acc 0.927 train_loss 0.00340
| epoch 3 | 1500/1782 batches| train_acc 0.923 train_loss 0.00354
---------------------------------------------------------------------
| epoch 3 | time:6.21s |valid_acc 0.935 | valid_loss 0.003
---------------------------------------------------------------------
| epoch 4 | 500/1782 batches| train_acc 0.933 train_loss 0.00306
| epoch 4 | 1000/1782 batches| train_acc 0.932 train_loss 0.00311
| epoch 4 | 1500/1782 batches| train_acc 0.929 train_loss 0.00318
---------------------------------------------------------------------
| epoch 4 | time:6.22s |valid_acc 0.916 | valid_loss 0.003
---------------------------------------------------------------------
| epoch 5 | 500/1782 batches| train_acc 0.948 train_loss 0.00253
| epoch 5 | 1000/1782 batches| train_acc 0.949 train_loss 0.00242
| epoch 5 | 1500/1782 batches| train_acc 0.951 train_loss 0.00238
---------------------------------------------------------------------
| epoch 5 | time:6.23s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------
| epoch 6 | 500/1782 batches| train_acc 0.951 train_loss 0.00241
| epoch 6 | 1000/1782 batches| train_acc 0.952 train_loss 0.00236
| epoch 6 | 1500/1782 batches| train_acc 0.952 train_loss 0.00235
---------------------------------------------------------------------
| epoch 6 | time:6.26s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------
| epoch 7 | 500/1782 batches| train_acc 0.954 train_loss 0.00228
| epoch 7 | 1000/1782 batches| train_acc 0.951 train_loss 0.00238
| epoch 7 | 1500/1782 batches| train_acc 0.954 train_loss 0.00228
---------------------------------------------------------------------
| epoch 7 | time:6.26s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------
| epoch 8 | 500/1782 batches| train_acc 0.953 train_loss 0.00227
| epoch 8 | 1000/1782 batches| train_acc 0.955 train_loss 0.00224
| epoch 8 | 1500/1782 batches| train_acc 0.954 train_loss 0.00224
---------------------------------------------------------------------
| epoch 8 | time:6.32s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------
| epoch 9 | 500/1782 batches| train_acc 0.955 train_loss 0.00218
| epoch 9 | 1000/1782 batches| train_acc 0.953 train_loss 0.00227
| epoch 9 | 1500/1782 batches| train_acc 0.955 train_loss 0.00227
---------------------------------------------------------------------
| epoch 9 | time:6.24s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------
| epoch 10 | 500/1782 batches| train_acc 0.952 train_loss 0.00229
| epoch 10 | 1000/1782 batches| train_acc 0.955 train_loss 0.00220
| epoch 10 | 1500/1782 batches| train_acc 0.956 train_loss 0.00220
---------------------------------------------------------------------
| epoch 10 | time:6.29s |valid_acc 0.954 | valid_loss 0.002
---------------------------------------------------------------------

八、定义训练函数与评估函数

print('Checking the results of test dataset.')
test_acc, test_loss = evaluate(test_dataloader)
print('test accuracy {:8.3f}'.format(test_acc))

Checking the results of test dataset.
test accuracy    0.905

总结： 

1. 预训练词向量：使用GloVe、FastText等预训练词向量能显著提升性能

2. 正则化：合理使用dropout、权重衰减等技术防止过拟合

3. 超参数调优：学习率、批大小、隐藏层维度等对模型性能影响很大

4. 迁移学习：对于小数据集，考虑使用BERT等预训练模型进行微调