怎么在mobilenetV2中加入动态调整学习率代码
时间: 2024-02-13 10:02:38 浏览: 142
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在MobileNetV2中加入动态调整学习率的代码可以通过PyTorch的学习率调度器(lr_scheduler)来实现。下面是一个简单的例子:
```python
import torch.optim as optim
from torch.optim.lr_scheduler import ReduceLROnPlateau
# 定义优化器和损失函数
optimizer = optim.SGD(model.parameters(), lr=0.1, momentum=0.9, weight_decay=1e-4)
criterion = nn.CrossEntropyLoss()
# 定义学习率调度器
scheduler = ReduceLROnPlateau(optimizer, mode='max', factor=0.1, patience=5, verbose=True)
# 训练过程中在每个epoch结束时调用scheduler.step(val_acc)
for epoch in range(num_epochs):
train_loss = 0
train_acc = 0
val_loss = 0
val_acc = 0
# 训练
model.train()
for batch_idx, (data, target) in enumerate(train_loader):
optimizer.zero_grad()
output = model(data)
loss = criterion(output, target)
loss.backward()
optimizer.step()
train_loss += loss.item()
pred = output.argmax(dim=1, keepdim=True)
train_acc += pred.eq(target.view_as(pred)).sum().item()
# 验证
model.eval()
with torch.no_grad():
for batch_idx, (data, target) in enumerate(val_loader):
output = model(data)
loss = criterion(output, target)
val_loss += loss.item()
pred = output.argmax(dim=1, keepdim=True)
val_acc += pred.eq(target.view_as(pred)).sum().item()
# 计算准确率和损失值
train_loss /= len(train_loader.dataset)
train_acc /= len(train_loader.dataset)
val_loss /= len(val_loader.dataset)
val_acc /= len(val_loader.dataset)
# 动态调整学习率
scheduler.step(val_acc)
# 打印日志
print('Epoch: {}, Train Loss: {:.6f}, Train Acc: {:.6f}, Val Loss: {:.6f}, Val Acc: {:.6f}'.format(
epoch + 1, train_loss, train_acc, val_loss, val_acc))
```
在上面的代码中,使用了ReduceLROnPlateau调度器,它会监测验证集上的准确率,如果准确率在patience个epoch内不再提高,则降低学习率。具体地,调度器会在每个epoch结束时调用scheduler.step(val_acc),其中val_acc是验证集上的准确率。当准确率不再提高时,调度器会将学习率乘以factor(默认为0.1),以便模型收敛到最优解。在这个例子中,调度器会在patience=5个epoch内监测验证集上的准确率,如果准确率不再提高,则降低学习率。
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