When I run this code, something is wrong…

vgg = VGGNet()
if use_cuda:
# vgg.cuda()
vgg = torch.nn.DataParallel(vgg, [0, 1, 2])
for step in range(config.total_step):
# Extract multiple(5) conv feature vectors
target_features = vgg(target)   # error


target is in GPU_0
How to solve this? Thanks~