1 NLP分类之：FastText

0 数据

https://download.csdn.net/download/qq_28611929/88580520?spm=1001.2014.3001.5503

数据集合：0 NLP: 数据获取与EDA-CSDN博客

词嵌入向量文件： embedding_SougouNews.npz

词典文件：vocab.pkl

1 模型

基于fastText做词向量嵌入然后引入2-gram, 3-gram扩充，最后接入一个MLP即可；

fastText 是一个由 Facebook AI Research 实现的开源库，用于进行文本分类和词向量学习。它结合了传统的词袋模型和神经网络的优点，能够快速训练大规模的文本数据。

fastText 的主要特点包括：

1. 快速训练：fastText 使用了层次化 Softmax 和负采样等技术，大大加快了训练速度。

2. 子词嵌入：fastText 将单词表示为字符级别的 n-gram，并将其视为单词的子词。这样可以更好地处理未登录词和稀有词。

3. 文本分类：fastText 提供了一个简单而高效的文本分类接口，可以用于训练和预测多类别文本分类任务。

4. 多语言支持：fastText 支持多种语言，并且可以通过学习共享词向量来提高跨语言任务的性能。

需要注意的是，fastText 主要适用于文本分类任务，对于其他类型的自然语言处理任务（如命名实体识别、机器翻译等），可能需要使用其他模型或方法。

 2 代码

nn.Embedding.from_pretrained(config.embedding_pretrained, freeze=False)
 

`nn.Embedding.from_pretrained` 是 PyTorch 中的一个函数，用于从预训练的词向量加载 Embedding 层的权重。

在使用 `nn.Embedding.from_pretrained` 时，你需要提供一个预训练的词向量矩阵作为参数，

freeze 参数： 指定是否冻结该层的权重。预训练的词向量可以是从其他模型（如 Word2Vec 或 GloVe）中得到的。

y = nn.Embedding.from_pretrained （x）

x输入：词的索引

y返回： 词向量

import pandas as pd
import torch
import torch.nn as nn
import torch.nn.functional as F
import numpy as np
import pickle as pkl
from tqdm import tqdm
import time
from torch.utils.data import Dataset

from datetime import timedelta
from sklearn.model_selection import train_test_split
from torch.utils.data import Dataset, DataLoader
from collections import defaultdict
from torch.optim import AdamW

UNK, PAD = '<UNK>', '<PAD>'  # 未知字，padding符号
RANDOM_SEED = 2023


file_path = "./data/online_shopping_10_cats.csv"
vocab_file = "./data/vocab.pkl"
emdedding_file = "./data/embedding_SougouNews.npz"
vocab = pkl.load(open(vocab_file, 'rb'))

class MyDataSet(Dataset):
    def __init__(self, df, vocab,pad_size=None):
        self.data_info = df
        self.data_info['review'] = self.data_info['review'].apply(lambda x:str(x).strip())
        self.data_info = self.data_info[['review','label']].values
        self.vocab = vocab 
        self.pad_size = pad_size
        self.buckets = 250499  
        
    def biGramHash(self,sequence, t):
        t1 = sequence[t - 1] if t - 1 >= 0 else 0
        return (t1 * 14918087) % self.buckets
        
    def triGramHash(self,sequence, t):
        t1 = sequence[t - 1] if t - 1 >= 0 else 0
        t2 = sequence[t - 2] if t - 2 >= 0 else 0
        return (t2 * 14918087 * 18408749 + t1 * 14918087) % self.buckets
        
    def __getitem__(self, item):
        result = {}
        view, label = self.data_info[item]
        result['view'] = view.strip()
        result['label'] = torch.tensor(label,dtype=torch.long)
        
        token = [i for i in view.strip()]
        seq_len = len(token)
        # 填充
        if self.pad_size:
            if len(token) < self.pad_size:
                token.extend([PAD] * (self.pad_size - len(token)))
            else:
                token = token[:self.pad_size]
                seq_len = self.pad_size
        result['seq_len'] = seq_len
        
        # 词表的转换
        words_line = []
        for word in token:
            words_line.append(self.vocab.get(word, self.vocab.get(UNK)))
        result['input_ids'] = torch.tensor(words_line, dtype=torch.long) 
        
        # 
        bigram = []
        trigram = []
        for i in range(self.pad_size):
            bigram.append(self.biGramHash(words_line, i))
            trigram.append(self.triGramHash(words_line, i))
            
        result['bigram'] = torch.tensor(bigram, dtype=torch.long)
        result['trigram'] = torch.tensor(trigram, dtype=torch.long)
        return result

    def __len__(self):
        return len(self.data_info)
df = pd.read_csv("./data/online_shopping_10_cats.csv")

#myDataset[0]
df_train, df_test = train_test_split(df, test_size=0.1, random_state=RANDOM_SEED)
df_val, df_test = train_test_split(df_test, test_size=0.5, random_state=RANDOM_SEED)
df_train.shape, df_val.shape, df_test.shape

def create_data_loader(df,vocab,pad_size,batch_size=4):
    ds = MyDataSet(df,
                   vocab,
                   pad_size=pad_size
                  )
    return DataLoader(ds,batch_size=batch_size)

MAX_LEN = 256
BATCH_SIZE = 4
train_data_loader = create_data_loader(df_train,vocab,pad_size=MAX_LEN, batch_size=BATCH_SIZE)
val_data_loader = create_data_loader(df_val,vocab,pad_size=MAX_LEN, batch_size=BATCH_SIZE)
test_data_loader = create_data_loader(df_test,vocab,pad_size=MAX_LEN, batch_size=BATCH_SIZE)

class Config(object):

    """配置参数"""
    def __init__(self):
        self.model_name = 'FastText'
        self.embedding_pretrained = torch.tensor(
            np.load("./data/embedding_SougouNews.npz")["embeddings"].astype('float32'))  # 预训练词向量
            
        self.device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')   # 设备

        self.dropout = 0.5                                              # 随机失活
        self.require_improvement = 1000                                 # 若超过1000batch效果还没提升，则提前结束训练
        self.num_classes = 2                                            # 类别数
        self.n_vocab = 0                                                # 词表大小，在运行时赋值
        self.num_epochs = 20                                            # epoch数
        self.batch_size = 128                                           # mini-batch大小
        self.learning_rate = 1e-4                                       # 学习率
        self.embed = self.embedding_pretrained.size(1)\
            if self.embedding_pretrained is not None else 300           # 字向量维度
        self.hidden_size = 256                                          # 隐藏层大小
        self.n_gram_vocab = 250499                                      # ngram 词表大小

class Model(nn.Module):
    def __init__(self, config):
        super(Model, self).__init__()
        if config.embedding_pretrained is not None:
            self.embedding = nn.Embedding.from_pretrained(config.embedding_pretrained, freeze=False)
        else:
            self.embedding = nn.Embedding(config.n_vocab, config.embed, padding_idx=config.n_vocab - 1)
        self.embedding_ngram2 = nn.Embedding(config.n_gram_vocab, config.embed)
        self.embedding_ngram3 = nn.Embedding(config.n_gram_vocab, config.embed)
        self.dropout = nn.Dropout(config.dropout)
        self.fc1 = nn.Linear(config.embed * 3, config.hidden_size)
        # self.dropout2 = nn.Dropout(config.dropout)
        self.fc2 = nn.Linear(config.hidden_size, config.num_classes)

    def forward(self, x):
        
        out_word = self.embedding(x['input_ids'])
        out_bigram = self.embedding_ngram2(x['bigram'])
        out_trigram = self.embedding_ngram3(x['trigram'])
        out = torch.cat((out_word, out_bigram, out_trigram), -1)

        out = out.mean(dim=1)
        out = self.dropout(out)
        out = self.fc1(out)
        out = F.relu(out)
        out = self.fc2(out)
        return out

config = Config()
model = Model(config)

device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
model = model.to(device)
 
EPOCHS = 5 # 训练轮数
optimizer = AdamW(model.parameters(),lr=2e-4)
total_steps = len(train_data_loader) * EPOCHS
# schedule = get_linear_schedule_with_warmup(optimizer,num_warmup_steps=0,
#                                num_training_steps=total_steps)
loss_fn = nn.CrossEntropyLoss().to(device)

def train_epoch(model,data_loader,loss_fn,device,n_exmaples,schedule=None):
    model = model.train()
    losses = []
    correct_predictions = 0
    for d in tqdm(data_loader):
        # input_ids = d['input_ids'].to(device)
        # attention_mask = d['attention_mask'].to(device)
        targets = d['label']#.to(device)
        outputs = model(d)
        
        _,preds = torch.max(outputs, dim=1)
        loss = loss_fn(outputs,targets)
        losses.append(loss.item())
        
        correct_predictions += torch.sum(preds==targets)
        loss.backward()
        nn.utils.clip_grad_norm_(model.parameters(), max_norm=1.0)
        optimizer.step()
        #scheduler.step()
        optimizer.zero_grad()
    return correct_predictions.double() / n_examples, np.mean(losses)
 
def eval_model(model, data_loader, loss_fn, device, n_examples):
    model = model.eval() # 验证预测模式
 
    losses = []
    correct_predictions = 0
 
    with torch.no_grad():
        for d in data_loader:
            targets = d['label']#.to(device)
            outputs = model(d)
            _, preds = torch.max(outputs, dim=1)
 
            loss = loss_fn(outputs, targets)
 
            correct_predictions += torch.sum(preds == targets)
            losses.append(loss.item())
 
    return correct_predictions.double() / n_examples, np.mean(losses)

# train model
EPOCHS = 5
history = defaultdict(list) # 记录10轮loss和acc
best_accuracy = 0
 
for epoch in range(EPOCHS):
 
    print(f'Epoch {epoch + 1}/{EPOCHS}')
    print('-' * 10)
 
    train_acc, train_loss = train_epoch(
        model,
        train_data_loader,
        loss_fn,
        optimizer,
        device,
        len(df_train)
    )
 
    print(f'Train loss {train_loss} accuracy {train_acc}')
 
    val_acc, val_loss = eval_model(
        model,
        val_data_loader,
        loss_fn,
        device,
        len(df_val)
    )
 
    print(f'Val   loss {val_loss} accuracy {val_acc}')
    print()
 
    history['train_acc'].append(train_acc)
    history['train_loss'].append(train_loss)
    history['val_acc'].append(val_acc)
    history['val_loss'].append(val_loss)
 
    if val_acc > best_accuracy:
        torch.save(model.state_dict(), 'best_model_state.bin')
        best_accuracy = val_acc

备注： CPU训练模型很慢啊！！！有GPU的用GPU吧。大家有想了解的可以私聊。

平均 1epoch / h;

Epoch 1/10
----------

100%|██████████████████████████████████| 14124/14124 [10:25:00<00:00,  2.66s/it]

Train loss 0.30206009501767567 accuracy 0.9164365618804872
Val   loss 0.335533762476819 accuracy 0.9111181905065308

Epoch 2/10
----------

100%|███████████████████████████████████| 14124/14124 [1:40:00<00:00,  2.35it/s]

Train loss 0.2812397742334814 accuracy 0.924667233078448
Val   loss 0.33604823821747 accuracy 0.9114367633004141

Epoch 3/10
----------

100%|███████████████████████████████████| 14124/14124 [1:26:10<00:00,  2.73it/s]

Train loss 0.26351333512826924 accuracy 0.9319420843953554
Val   loss 0.3722937448388443 accuracy 0.9082510353615801