Hello,
As a part of a computation, I need to access a member of an output variable after I do a backward pass on it. The weird thing is, if I do this in GPU, this access takes a lot of time compared to doing this in CPU. In the code snippet below, I is an image with size 3x224x224 and network is resnet50 from the models:
x = Variable(I.unsqueeze_(0).cuda(),requires_grad=True)  
net.cuda()
output = net(x)
ff = output.data.squeeze()

output[:,10].backward()

alp = ff[100]

Now, normally I expect the last line to take less than a milisecond and this is the case if I do not use the GPU (if I remove the .cuda()s). However, in this case, it takes around 100 ms. Is there a problem? Is the computer alp from the GPU memory and that is causing the issue? Or am I doing something wrong?