在使用BertForSequenceClassification类进行分类任务时,可能会遇到度量不匹配的问题。这通常是因为自定义的Bert分类器使用了不同的度量方法或评估指标。下面是一种解决方法的示例代码:
from transformers import BertTokenizer, BertForSequenceClassification
from sklearn.metrics import accuracy_score
# 加载Bert模型和tokenizer
model = BertForSequenceClassification.from_pretrained('bert-base-uncased')
tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
# 自定义Bert分类器
class MyBertClassifier:
def __init__(self, model, tokenizer):
self.model = model
self.tokenizer = tokenizer
def predict(self, text):
# 对文本进行tokenize和编码
input_ids = self.tokenizer.encode(text, add_special_tokens=True)
input_ids = torch.tensor([input_ids])
# 使用Bert模型进行预测
outputs = self.model(input_ids)
logits = outputs.logits
predicted_labels = torch.argmax(logits, dim=1)
return predicted_labels.tolist()[0]
def evaluate(self, texts, labels):
predicted_labels = [self.predict(text) for text in texts]
accuracy = accuracy_score(labels, predicted_labels)
return accuracy
# 样本数据
texts = ['This is a positive example.', 'This is a negative example.']
labels = [1, 0]
# 使用BertForSequenceClassification类进行评估
model = BertForSequenceClassification.from_pretrained('bert-base-uncased')
tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
encoded_inputs = tokenizer(texts, padding=True, truncation=True, return_tensors='pt')
labels = torch.tensor(labels)
outputs = model(**encoded_inputs, labels=labels)
loss = outputs.loss
predicted_labels = torch.argmax(outputs.logits, dim=1)
accuracy = accuracy_score(labels.tolist(), predicted_labels.tolist())
print("BertForSequenceClassification accuracy:", accuracy)
# 使用自定义的Bert分类器进行评估
my_classifier = MyBertClassifier(model, tokenizer)
my_accuracy = my_classifier.evaluate(texts, labels)
print("MyBertClassifier accuracy:", my_accuracy)
在上述示例代码中,我们定义了一个名为MyBertClassifier
的自定义Bert分类器。它接受一个Bert模型和一个tokenizer作为参数,并在predict
方法中使用Bert模型进行预测。在evaluate
方法中,我们计算预测标签与真实标签之间的准确性。
通过与BertForSequenceClassification
类进行比较,我们可以看到两种方法的度量结果是否匹配。在这个例子中,我们使用了准确性作为度量指标。