英文文本关系抽取（fine-tune Huggingface XLNet）

迷南。 2022-12-11 03:28 144阅读 0赞

本文主要是基于[英文文本关系抽取][Link 1]比赛，讲解如何fine-tune Huggingface的预训练模型，同时可以看作是关系抽取的一个简单案例

### 数据预览 ###

训练数据包含两列。第一列是文本，其中`<e1></e1>`包起来的是第一个实体，`<e2></e2>`包起来的是第二个实体。第二列是关系，除了"Other"这个关系以外，其它关系都有先后顺序，比方说第一个样本：“伤害是由邀请制度造成的”，其中"harm"是因果关系中的果，而"system"是因，所以最终label是"Cause-Effect(e2,e1)"

![723b3fc33a121c973fe7222dd0a7bca2.png_shadow][]

### 思路 ###

总体来说都是用Huggingface的预训练模型做fine-tune，但是具体怎么做有很多种方法

#### 第一种方法 ####

由于label非常特殊，不光要预测实体之间的关系，还要预测其顺序，因此可以考虑预测三个值，具体如下图所示（以第一个句子为例）

![44a1ff173a6998a8816c9925225565a8.png_shadow][]

`[CLS]`位置的输出会做一个10分类，而两个实体对应的输出分别做一个3分类。这个3分类是有讲究的，分类为0只有一种情况，就是当`[CLS]`的输出预测为"Other"的时候，因为"Other"是不需要考虑两个实体的顺序的；另外，假如"harm"预测为1，"system"预测为2，表示在当前这个关系中"harm"的顺序在"system"的前面，反之一样的道理。通过预测三个值，就可以唯一确定一个关系了

#### 第二种方法 ####

先看下图，具体来说就是将两个实体的输出拼接在一起，然后做一个18分类

![cfd3d9faf4646329142e74dd04835728.png_shadow][]

#### 第三种方法 ####

这是最简单的一种方法，本文使用的也是这种方法。直接将`[CLS]`的输出进行一个18分类

![f79840cfb8bcbf63b2c083d24e63db29.png_shadow][]

其实还有其他更多方法，大家自己下去尝试即可

### Data Preprocessing ###

def process_data(filename):
        with open(filename) as f:
            rows = [row for row in csv.reader(f)]
            rows = np.array(rows[1:]) # all data, 2D
            label_list = [label for _, label in rows] # label list
            global classes_list
            classes_list = list(set(label_list)) # non-repeated label list
            num_classes = len(classes_list) # num of classes
            for i in range(len(label_list)):
                label_list[i] = classes_list.index(label_list[i]) # index of label
    
            name_list, sentence_list = [], []
            for sentence, _ in rows:
                begin = sentence.find('<e1>')
                end = sentence.find('</e1>')
                e1 = sentence[begin:end + 5]
    
                begin = sentence.find('<e2>')
                end = sentence.find('</e2>')
                e2 = sentence[begin:end + 5]
                
                name_list.append(e1 + " " + e2)
                sentence_list.append(sentence)
        print(num_classes)
        return name_list, sentence_list, label_list, classes_list, num_classes

`name_list`是个一维的list，里面存了每一行文本中两个实体的名称，两个实体之间用空格隔开。`sentence_list`是个一维的list，里面存了每一行文本。`label_list`是个一维的list，里面的值是int类型的，就是将原本str类型的label标签转为对应的index。`classes_list`就是去重后的label。`num_classes`就是`len(classes_list)`

这里我用的是第三种思路做的，因此后面是用不到`name_list`的，但我还是将其提取出来，方便后面读者调用

### XLNetTokenizer ###

接下来要做的是将提取出来的`sentence_list`经过`XLNetTokenizer`，以每句话为单位，获取一句话中所有词的索引，attention mask等相关内容

tokenizer = XLNetTokenizer.from_pretrained('xlnet-base-cased')
    
    def convert(names, sentences, target): # name_list, sentence_list, label_list
        input_ids, token_type_ids, attention_mask = [], [], []
        for i in range(len(sentences)):
            encoded_dict = tokenizer.encode_plus(
                sentences[i],        # 输入文本
                add_special_tokens = True,      # 添加 '[CLS]' 和 '[SEP]'
                max_length = 96,           # 填充 & 截断长度
                pad_to_max_length = True,
                return_tensors = 'pt',         # 返回 pytorch tensors 格式的数据
            )
            input_ids.append(encoded_dict['input_ids'])
            token_type_ids.append(encoded_dict['token_type_ids'])
            attention_mask.append(encoded_dict['attention_mask'])
    
        input_ids = torch.cat(input_ids, dim=0)
        token_type_ids = torch.cat(token_type_ids, dim=0)
        attention_mask = torch.cat(attention_mask, dim=0)
    
        input_ids = torch.LongTensor(input_ids)
        token_type_ids = torch.LongTensor(token_type_ids)
        attention_mask = torch.LongTensor(attention_mask)
        target = torch.LongTensor(target)
    
        return input_ids, token_type_ids, attention_mask, target

### Train Test Split ###

为了验证模型效果，所以我们将从训练数据中划分一部分作为验证集，只需调用sklearn中的`train_test_split`方法即可

train_inputs, val_inputs, train_labels, val_labels = train_test_split(input_ids, labels, random_state=1, test_size=0.1)
    train_token, val_token, _, _ = train_test_split(token_type_ids, labels, random_state=1, test_size=0.1)
    train_mask, val_mask, _, _ = train_test_split(attention_mask, labels, random_state=1, test_size=0.1)
    
    train_data = Data.TensorDataset(train_inputs, train_token, train_mask, train_labels)
    train_dataloader = Data.DataLoader(train_data, batch_size=batch_size, shuffle=True)
    
    validation_data = Data.TensorDataset(val_inputs, val_token, val_mask, val_labels)
    validation_dataloader = Data.DataLoader(validation_data, batch_size=batch_size, shuffle=True)

这里需要注意的是，由于每个样本的ids，token，mask是一一对应的，所以我们必须设置三个`train_test_split`方法中的`random_state`值相等，否则他们拆分得到的数据就乱了

### XLNetForSequenceClassification ###

由于这里我是用的是简单的句子分类思路，直接调用Huggingface中有现成的API即可（注意设定分类个数）。下面的代码参考自Huggingface Docs中的[Training and fine-tuning][]

model = XLNetForSequenceClassification.from_pretrained('xlnet-base-cased', num_labels=num_classes).to(device)
    
    param_optimizer = list(model.named_parameters())
    no_decay = ['bias', 'gamma', 'beta']
    optimizer_grouped_parameters = [
        {
        'params': [p for n, p in param_optimizer if not any(nd in n for nd in no_decay)],
        'weight_decay_rate': 0.01},
        {
        'params': [p for n, p in param_optimizer if any(nd in n for nd in no_decay)],
        'weight_decay_rate': 0.0}]
    
    optimizer = AdamW(optimizer_grouped_parameters, lr=1e-5)

### Train & Val ###

训练的时候，直接传给model指定的参数即可

for _ in range(2):
        for i, batch in enumerate(train_dataloader):
            batch = tuple(t.to(device) for t in batch)
            loss = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2], labels=batch[3])[0]
            print(loss.item())
    
            optimizer.zero_grad()
            loss.backward()
            optimizer.step()
    
            if i % 10 == 0:
              eval(model, validation_dataloader)

这个model的返回值可以查看XLNetForSequenceClassificatiton的[API][]文档。如果需要loss进行反向传播，取出第一个值即可；如果需要预测值，则取出第二个值；如果需要每层、每个词的隐藏状态，则取出第四个值

![084c4cd22a091ac64c861fca38e4408c.png_shadow][]

在训练的过程中，每经过10个epoch，就在验证集上测试一次。**在validation以及test时我们是不会传给模型真实标签的，因此模型也不会返回loss，所以此时模型返回的第一个值不再是loss，而是logits**

def flat_accuracy(preds, labels):
        pred_flat = np.argmax(preds, axis=1).flatten() # [3, 5, 8, 1, 2, ....]
        labels_flat = labels.flatten()
        return np.sum(pred_flat == labels_flat) / len(labels_flat)
    
    def eval(model, validation_dataloader):
        model.eval()
        eval_loss, eval_accuracy, nb_eval_steps = 0, 0, 0
        for batch in validation_dataloader:
            batch = tuple(t.to(device) for t in batch)
            with torch.no_grad():
                logits = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2])[0]
                logits = logits.detach().cpu().numpy()
                label_ids = batch[3].cpu().numpy()
                tmp_eval_accuracy = flat_accuracy(logits, label_ids)
                eval_accuracy += tmp_eval_accuracy
                nb_eval_steps += 1
        print("Validation Accuracy: {}".format(eval_accuracy / nb_eval_steps))
        global best_score
        if best_score < eval_accuracy / nb_eval_steps:
            best_score = eval_accuracy / nb_eval_steps
            save(model)

在验证集上计算准确率的同时，保存到目前为止在验证集上准确率最高的模型参数，后面真正做测试的时候就用这个参数。下面的代码涉及到保存模型的操作

output_dir = './models/'
    output_model_file = os.path.join(output_dir, WEIGHTS_NAME)
    output_config_file = os.path.join(output_dir, CONFIG_NAME)
    
    def save(model):
        # save
        torch.save(model.state_dict(), output_model_file)
        model.config.to_json_file(output_config_file)

如果要加载模型，只需要一行代码即可

# load model
    model = XLNetForSequenceClassification.from_pretrained(output_dir).to(device)

### Test ###

def pred():
        # load model
        model = XLNetForSequenceClassification.from_pretrained(output_dir).to(device)
    
        sentence_list = []
        with open('test.csv') as f:
            rows = [row for row in csv.reader(f)]
            rows = np.array(rows[1:])
            sentence_list = [text for idx, text in rows]
    
        input_ids, token_type_ids, attention_mask, _ = convert(['test'], sentence_list, [1]) # whatever name_list and label_list
        dataset = Data.TensorDataset(input_ids, token_type_ids, attention_mask)
        loader = Data.DataLoader(dataset, 32, False)
    
        pred_label = []
        model.eval()
        for i, batch in enumerate(loader):
            batch = tuple(t.to(device) for t in batch)
            with torch.no_grad():
                logits = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2])[0]
                logits = logits.detach().cpu().numpy()
                preds = np.argmax(logits, axis=1).flatten()
                pred_label.extend(preds)
        
        for i in range(len(pred_label)):
            pred_label[i] = classes_list[pred_label[i]]
    
        pd.DataFrame(data=pred_label, index=range(len(pred_label))).to_csv('pred.csv')

其实这里没有用到`name_list`和真实的标签，但是为了能复用前面的`convert()`函数，保证函数参数一致，所以我随便传了两个参数`['test']`和`[1]`

### Code ###

import os
    import csv
    import torch
    import logging
    import numpy as np
    import pandas as pd
    from transformers import *
    import torch.utils.data as Data
    from sklearn.model_selection import train_test_split
    
    logging.basicConfig(level=logging.ERROR)
    tokenizer = XLNetTokenizer.from_pretrained('xlnet-base-cased')
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    
    best_score = 0
    batch_size = 32
    classes_list = []
    
    output_dir = './models/'
    output_model_file = os.path.join(output_dir, WEIGHTS_NAME)
    output_config_file = os.path.join(output_dir, CONFIG_NAME)
    
    def process_data(filename):
        with open(filename) as f:
            rows = [row for row in csv.reader(f)]
            rows = np.array(rows[1:]) # all data, 2D
            label_list = [label for _, label in rows] # label list
            global classes_list
            classes_list = list(set(label_list)) # non-repeated label list
            num_classes = len(classes_list) # num of classes
            for i in range(len(label_list)):
                label_list[i] = classes_list.index(label_list[i]) # index of label
    
            name_list, sentence_list = [], []
            for sentence, _ in rows:
                begin = sentence.find('<e1>')
                end = sentence.find('</e1>')
                e1 = sentence[begin:end + 5]
    
                begin = sentence.find('<e2>')
                end = sentence.find('</e2>')
                e2 = sentence[begin:end + 5]
                
                name_list.append(e1 + " " + e2)
                sentence_list.append(sentence)
        print(num_classes)
        return name_list, sentence_list, label_list, classes_list, num_classes
    
    def convert(names, sentences, target): # name_list, sentence_list, label_list
        input_ids, token_type_ids, attention_mask = [], [], []
        for i in range(len(sentences)):
            encoded_dict = tokenizer.encode_plus(
                sentences[i],        # 输入文本
                add_special_tokens = True,      # 添加 '[CLS]' 和 '[SEP]'
                max_length = 96,           # 填充 & 截断长度
                pad_to_max_length = True,
                return_tensors = 'pt',         # 返回 pytorch tensors 格式的数据
            )
            input_ids.append(encoded_dict['input_ids'])
            token_type_ids.append(encoded_dict['token_type_ids'])
            attention_mask.append(encoded_dict['attention_mask'])
    
        input_ids = torch.cat(input_ids, dim=0)
        token_type_ids = torch.cat(token_type_ids, dim=0)
        attention_mask = torch.cat(attention_mask, dim=0)
    
        input_ids = torch.LongTensor(input_ids)
        token_type_ids = torch.LongTensor(token_type_ids)
        attention_mask = torch.LongTensor(attention_mask)
        target = torch.LongTensor(target)
    
        return input_ids, token_type_ids, attention_mask, target
    
    def flat_accuracy(preds, labels):
        pred_flat = np.argmax(preds, axis=1).flatten() # [3, 5, 8, 1, 2, ....]
        labels_flat = labels.flatten()
        return np.sum(pred_flat == labels_flat) / len(labels_flat)
    
    def save(model):
        # save
        torch.save(model.state_dict(), output_model_file)
        model.config.to_json_file(output_config_file)
    
    
    def eval(model, validation_dataloader):
        model.eval()
        eval_loss, eval_accuracy, nb_eval_steps = 0, 0, 0
        for batch in validation_dataloader:
            batch = tuple(t.to(device) for t in batch)
            with torch.no_grad():
                logits = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2])[0]
                logits = logits.detach().cpu().numpy()
                label_ids = batch[3].cpu().numpy()
                tmp_eval_accuracy = flat_accuracy(logits, label_ids)
                eval_accuracy += tmp_eval_accuracy
                nb_eval_steps += 1
        print("Validation Accuracy: {}".format(eval_accuracy / nb_eval_steps))
        global best_score
        if best_score < eval_accuracy / nb_eval_steps:
            best_score = eval_accuracy / nb_eval_steps
            save(model)
    
    def train_val():
        name_list, sentence_list, label_list, _, num_classes = process_data('train.csv')
        input_ids, token_type_ids, attention_mask, labels = convert(name_list, sentence_list, label_list)
    
        train_inputs, val_inputs, train_labels, val_labels = train_test_split(input_ids, labels, random_state=1, test_size=0.1)
        train_token, val_token, _, _ = train_test_split(token_type_ids, labels, random_state=1, test_size=0.1)
        train_mask, val_mask, _, _ = train_test_split(attention_mask, labels, random_state=1, test_size=0.1)
        
        train_data = Data.TensorDataset(train_inputs, train_token, train_mask, train_labels)
        train_dataloader = Data.DataLoader(train_data, batch_size=batch_size, shuffle=True)
    
        validation_data = Data.TensorDataset(val_inputs, val_token, val_mask, val_labels)
        validation_dataloader = Data.DataLoader(validation_data, batch_size=batch_size, shuffle=True)
    
        model = XLNetForSequenceClassification.from_pretrained('xlnet-base-cased', num_labels=num_classes).to(device)
    
        param_optimizer = list(model.named_parameters())
        no_decay = ['bias', 'gamma', 'beta']
        optimizer_grouped_parameters = [
            {
        'params': [p for n, p in param_optimizer if not any(nd in n for nd in no_decay)],
            'weight_decay_rate': 0.01},
            {
        'params': [p for n, p in param_optimizer if any(nd in n for nd in no_decay)],
            'weight_decay_rate': 0.0}]
    
        optimizer = AdamW(optimizer_grouped_parameters, lr=1e-5)
    
        for _ in range(2):
            for i, batch in enumerate(train_dataloader):
                batch = tuple(t.to(device) for t in batch)
                loss = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2], labels=batch[3])[0]
                print(loss.item())
    
                optimizer.zero_grad()
                loss.backward()
                optimizer.step()
                
                if i % 10 == 0:
                  eval(model, validation_dataloader)
    
    def pred():
        # load model
        model = XLNetForSequenceClassification.from_pretrained(output_dir).to(device)
    
        sentence_list = []
        with open('test.csv') as f:
            rows = [row for row in csv.reader(f)]
            rows = np.array(rows[1:])
            sentence_list = [text for idx, text in rows]
    
        input_ids, token_type_ids, attention_mask, _ = convert(['test'], sentence_list, [1]) # whatever name_list and label_list
        dataset = Data.TensorDataset(input_ids, token_type_ids, attention_mask)
        loader = Data.DataLoader(dataset, 32, False)
    
        pred_label = []
        model.eval()
        for i, batch in enumerate(loader):
            batch = tuple(t.to(device) for t in batch)
            with torch.no_grad():
                logits = model(batch[0], token_type_ids=batch[1], attention_mask=batch[2])[0]
                logits = logits.detach().cpu().numpy()
                preds = np.argmax(logits, axis=1).flatten()
                pred_label.extend(preds)
        
        for i in range(len(pred_label)):
            pred_label[i] = classes_list[pred_label[i]]
    
        pd.DataFrame(data=pred_label, index=range(len(pred_label))).to_csv('pred.csv')
    
    if __name__ == '__main__':
        train_val()
        pred()

[Link 1]: https://god.yanxishe.com/82
[723b3fc33a121c973fe7222dd0a7bca2.png_shadow]: /images/20221123/2365b361a5eb47b1aa3800b85fba2f4e.png
[44a1ff173a6998a8816c9925225565a8.png_shadow]: /images/20221123/7fbef03dcee547f6876f17d8f39eed73.png
[cfd3d9faf4646329142e74dd04835728.png_shadow]: /images/20221123/38034981daad4654beb223ce207fde09.png
[f79840cfb8bcbf63b2c083d24e63db29.png_shadow]: /images/20221123/aa9acbd2f354445194dcdc9feea0ec16.png
[Training and fine-tuning]: https://huggingface.co/transformers/training.html
[API]: https://huggingface.co/transformers/model_doc/xlnet.html#xlnetforsequenceclassification
[084c4cd22a091ac64c861fca38e4408c.png_shadow]: /images/20221123/5188f6029a8443a6b9180f0eb2cc3ceb.png