單GPU：

import os
os.environ["CUDA_VISIBLE_DEVICES"] = "0"

多GPU：

device_ids = [0,1,2,3]

model = model.cuda(device_ids[0])
model = nn.DataParallel(model, device_ids=device_ids)

optimizer = optim.SGD(model.parameters(), lr=learning_rate, momentum=0.9, weight_decay=0.001)
optimizer = nn.DataParallel
 
(optimizer, device_ids=device_ids)

optimizer.module.step()

for param_lr in optimizer.module.param_groups:  # 同樣是要加module
        #     param_lr['lr'] = param_lr['lr'] * 0.999

載入多GPU預訓練模型

model = ft_net()
pretained_model = torch.load('./model/all/8_model.pkl')
pretained_dict = pretained_model.module
 
.state_dict()
model = ft_net()
model.load_state_dict(pretained_dict)