title: PyTorch's DataParallel is only using one GPU
body: <p>I'm trying to use two GPU's for training a model in PyTorch. I'm using <code>torch.nn.DataParallel</code> but for some reason <code>nvidia-smi</code> is saying that I'm only using one GPU.</p>
  <p>The code is something along the lines of:</p>
  <pre><code>&gt;&gt;&gt; import torch.nn as nn 
  &gt;&gt;&gt; model = SomeModel()
  &gt;&gt;&gt; model = nn.DataParallel(model)
  &gt;&gt;&gt; model.to('cuda')
  </code></pre>
  <p>When I run the program and observe the output of <code>nvidia-smi</code>, I only see GPU 0 running. Would anybody know what the problem is?</p>