基于BiLSTM-CRF对清华语料文本进行分类

 安装TorchCRF

!pip install TorchCRF==1.0.6

构建BiLSTM-CRF

# encoding:utf-8

import torch
import torch.nn as nn
from TorchCRF import CRF

from torch.utils.data import Dataset
from sklearn.model_selection import train_test_split
import numpy as np

import torch
import torch.nn as nn
import torch.optim as op
from torch.utils.data import DataLoader

import torch
from sklearn.metrics import precision_score
from sklearn.metrics import recall_score
from sklearn.metrics import f1_score
from sklearn.metrics import classification_report

# 命名体识别数据


class NERDataset(Dataset):
    def __init__(self, X, Y, *args, **kwargs):
        self.data = [{'x': X[i], 'y': Y[i]} for i in range(X.shape[0])]

    def __getitem__(self, index):
        return self.data[index]

    def __len__(self):
        return len(self.data)

# LSTM_CRF模型
class NERLSTM_CRF(nn.Module):
    def __init__(self, config):
        super(NERLSTM_CRF, self).__init__()

        self.embedding_dim = config.embedding_dim
        self.hidden_dim = config.hidden_dim
        self.vocab_size = config.vocab_size
        self.num_tags = config.num_tags

        self.embeds = nn.Embedding(self.vocab_size, self.embedding_dim)
        self.dropout = nn.Dropout(config.dropout)

        self.lstm = nn.LSTM(
            self.embedding_dim,
            self.hidden_dim // 2,
            num_layers=1,
            bidirectional=True,
            batch_first=True,  # 该属性设置后，需要特别注意数据的形状
        )

        self.linear = nn.Linear(self.hidden_dim, self.num_tags)

        # CRF 层
        self.crf = CRF(self.num_tags)

    def forward(self, x, mask):
        embeddings = self.embeds(x)
        feats, hidden = self.lstm(embeddings)
        emissions = self.linear(self.dropout(feats))
        outputs = self.crf.viterbi_decode(emissions, mask)
        return outputs

    def log_likelihood(self, x, labels, mask):
        embeddings = self.embeds(x)
        feats, hidden = self.lstm(embeddings)
        emissions = self.linear(self.dropout(feats))
        loss = -self.crf.forward(emissions, labels, mask)
        return torch.sum(loss)

# ner chinese

加载数据

tag2id = {"PAD":0, "B-LOC":1,"I-LOC":2, "B-PER":3, "I-PER":4, "B-ORG":5, "I-ORG":6, "O":7}
id2tag = {v:k for k, v in tag2id.items()}
tlp ="/kaggle/input/ner-bilstm-crf/data_txt/{}"


def load_text(name, word2id=None):
    lines = []
    if not word2id:
        word2id, flag = {"pad":0, "unk":1}, True
    else:
        flag = False

    with open(tlp.format(name), encoding="utf-8") as fp:
        buff = []
        for line in fp:
            if not line.strip():
                lines.append(buff)
                buff = []
            else:
                buff.append(line.strip())
    x_train, y_train, maxlen= [],[], 60
    for line in lines:
        x, y = [], []
        for v in line:
            w,t = v.split("\t")
            if w not in word2id and flag:
                word2id[w]=len(word2id)
            x.append(word2id.get(w, 1))
            y.append(tag2id[t])
        if len(x)

实体类型解码

#from read_file_pkl import load_data

word2id, tag2id, x_train, x_test, x_valid, y_train, y_test, y_valid, id2tag = load_data()


# 用于将实体类别解码，单字组合成单词
def parse_tags(text, path):
    tags = [id2tag[idx] for idx in path]

    begin = 0
    end = 0

    res = []
    for idx, tag in enumerate(tags):
        # 将连续的 同类型 的字连接起来
        if tag.startswith("B"):
            begin = idx
        elif tag.startswith("E"):
            end = idx
            word = text[begin:end + 1]
            label = tag[2:]
            res.append((word, label))
        elif tag=='O':
            res.append((text[idx], tag))
    return res


class Config:
    embedding_dim = 100
    hidden_dim = 200
    vocab_size = len(word2id)
    num_tags = len(tag2id)

    dropout = 0.2
    lr = 0.001
    weight_decay = 1e-5


def utils_to_train():
    device = torch.device('cpu')
    max_epoch = 1
    batch_size = 32
    num_workers = 4

    train_dataset = NERDataset(x_train, y_train)
    valid_dataset = NERDataset(x_valid, y_valid)
    test_dataset = NERDataset(x_test, y_test)

    train_data_loader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True, num_workers=num_workers)
    valid_data_loader = DataLoader(valid_dataset, batch_size=batch_size, shuffle=True, num_workers=num_workers)
    test_data_loader = DataLoader(test_dataset, batch_size=batch_size, shuffle=True, num_workers=num_workers)

    config = Config()
    model = NERLSTM_CRF(config).to(device)
    criterion = nn.CrossEntropyLoss(ignore_index=0)
    optimizer = op.Adam(model.parameters(), lr=config.lr, weight_decay=config.weight_decay)

    return max_epoch, device, train_data_loader, valid_data_loader, test_data_loader, optimizer, model

BiSTM-CRF训练

word2id = load_data()[0]
max_epoch, device, train_data_loader, valid_data_loader, test_data_loader, optimizer, model = utils_to_train()

# 中文命名体识别
class ChineseNER(object):
    def train(self):
        for epoch in range(max_epoch):

            # 训练模式
            model.train()

            for index, batch in enumerate(train_data_loader):
                # 梯度归零
                optimizer.zero_grad()

                # 训练数据-->gpu
                x = batch['x'].to(device)
                mask = (x > 0).to(device)
                y = batch['y'].to(device)

                # 前向计算计算损失
                loss = model.log_likelihood(x, y, mask)

                # 反向传播
                loss.backward()

                # 梯度裁剪
                torch.nn.utils.clip_grad_norm_(parameters=model.parameters(),
                                               max_norm=10)

                # 更新参数
                optimizer.step()
                if index % 200 == 0:
                    print('epoch:%5d,------------loss:%f' %
                          (epoch, loss.item()))

            # 验证损失和精度
            aver_loss = 0
            preds, labels = [], []
            for index, batch in enumerate(valid_data_loader):

                # 验证模式
                model.eval()

                # 验证数据-->gpu
                val_x, val_y = batch['x'].to(device), batch['y'].to(device)
                val_mask = (val_x > 0).to(device)
                predict = model(val_x, val_mask)

                # 前向计算损失
                loss = model.log_likelihood(val_x, val_y, val_mask)
                aver_loss += loss.item()

                # 统计非0的，也就是真实标签的长度
                leng = []
                res = val_y.cpu()
                for i in val_y.cpu():
                    tmp = []
                    for j in i:
                        if j.item() > 0:
                            tmp.append(j.item())
                    leng.append(tmp)

                for index, i in enumerate(predict):
                    preds += i[:len(leng[index])]

                for index, i in enumerate(val_y.tolist()):
                    labels += i[:len(leng[index])]

            # 损失值与评测指标
            aver_loss /= (len(valid_data_loader) * 64)
            precision = precision_score(labels, preds, average='macro')
            recall = recall_score(labels, preds, average='macro')
            f1 = f1_score(labels, preds, average='macro')
            report = classification_report(labels, preds)
            print(report)
            torch.save(model.state_dict(), 'params1.data_target_pkl')

    # 预测，输入为单句，输出为对应的单词和标签
    def predict(self, input_str=""):
        model.load_state_dict(torch.load("../models/ner/params1.data_target_pkl"))
        model.eval()
        if not input_str:
            input_str = input("请输入文本: ")

        input_vec = []
        for char in input_str:
            if char not in word2id:
                input_vec.append(word2id['[unknown]'])
            else:
                input_vec.append(word2id[char])

        # convert to tensor
        sentences = torch.tensor(input_vec).view(1, -1).to(device)
        mask = sentences > 0
        paths = model(sentences, mask)

        res = parse_tags(input_str, paths[0])
        return res

    # 在测试集上评判性能
    def test(self, test_dataloader):
        model.load_state_dict(torch.load("../models/ner/params1.data_target_pkl"))

        aver_loss = 0
        preds, labels = [], []
        for index, batch in enumerate(test_dataloader):

            # 验证模式
            model.eval()

            # 验证数据-->gpu
            val_x, val_y = batch['x'].to(device), batch['y'].to(device)
            val_mask = (val_x > 0).to(device)
            predict = model(val_x, val_mask)

            # 前向计算损失
            loss = model.log_likelihood(val_x, val_y, val_mask)
            aver_loss += loss.item()

            # 统计非0的，也就是真实标签的长度
            leng = []
            for i in val_y.cpu():
                tmp = []
                for j in i:
                    if j.item() > 0:
                        tmp.append(j.item())
                leng.append(tmp)

            for index, i in enumerate(predict):
                preds += i[:len(leng[index])]

            for index, i in enumerate(val_y.tolist()):
                labels += i[:len(leng[index])]

        # 损失值与评测指标
        aver_loss /= len(test_dataloader)
        precision = precision_score(labels, preds, average='macro')
        recall = recall_score(labels, preds, average='macro')
        f1 = f1_score(labels, preds, average='macro')
        report = classification_report(labels, preds)
        print(report)


if __name__ == '__main__':
    cn = ChineseNER()
    cn.train()

环境		TPU VM v3-8
	Precision	recall	F1-score	support
1	0.86	0.77	0.82	3209
2	0.82	0.76	0.79	4417
3	0.90	0.77	0.83	1591
4	0.90	0.80	0.85	3052
5	0.83	0.68	0.75	1896
6	0.84	0.79	0.82	7566
7	0.98	0.99	0.99	167824
Accuracy			0.97	189555
Macro avg	0.88	0.80	0.83	189555
Weighted avg	0.97	0.97	0.97	189555

表1 BiLSTM-CRF训练效果 

总体上，模型的Accuracy（整体正确率）为0.97，说明模型的预测效果较好。Macro avg和Weighted avg是分别对各个类别进行平均后的指标，Macro avg对每个类别的指标进行平均，Weighted avg对每个类别的指标进行加权平均。考虑了样本数的影响，类别7的Precision、recall和F1-score都较高，说明该类别的样本预测效果最好；而类别5的指标相对较低，说明该类别的样本预测效果最差。

操作异常问题与解决方案

1、ModuleNotFoundError: No module named “TorchCRF”

解决办法：pip install TorchCRF

2、 IndexError: tensors used as indices must be long, byte or bool tensors

解决办法：先卸载TorchCRF然后安装适配版本的TorchCRF

pip uninstall TorchCRF

pip install TorchCRF==1.0.6

3、IndexError:CUDA kernel errors might be asynchronously reported at some other API call,so the stacktrace below m

解决办法：添加以下代码，指定GPU运行

import os

os.environ['CUDA_LAUNCH_BLOCKING'] = '1'

6、BrokenPipeError: [Errno 32] Broken pipe

解决办法显存爆满，应该换用更大显存的GPU，因此选择使用kaggle运行

7、RuntimeError: Expected all tensors to be on the same device, but found at least two devices, cpu

解决办法：换用TPU进行运行

总结

本实验使用BiLSTM-CRF对文本进行分类，最终分类结果达到97%，分类效果较好。LSTM是一种能够对序列数据进行建模的循环神经网络，能够捕捉输入文本的上下文信息。而双向LSTM则是同时考虑正向和反向的上下文信息，进一步提高了模型的上下文信息捕捉能力。RF（Conditional Random Field）是一种无向图模型，能够对序列标注结果进行后验推断，从而更好地处理序列标注问题。

在文本分类中，可以将每个单词的特征作为节点，利用CRF进行动态规划解码，找出最优的分类结果。