Hi,
I cannot reproduce this with latest pytorch:
In [1]: import torch

In [2]: from torch import nn

In [3]: net = nn.Linear(2, 1).cuda()
data
In [4]: data = torch.randn(16, 2).cuda()

In [5]: ou1 = net(data)

In [6]: ou2 = net(data)

In [7]: ou1 - ou2
Out[7]: 
tensor([[0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.],
        [0.]], device='cuda:0', grad_fn=<SubBackward0>)

This can either be a bug that has been fixed or a install/hardware issue.
Do you see the same thing when running on a different machine?