title: Timeout in multi-machine training of pytorch?
body: <p>Error occurs in multi-machine training of pytorch:</p>
  <pre><code>RuntimeError: [/pytorch/third_party/gloo/gloo/transport/tcp/unbound_buffer.cc:136] Timed out waiting 1800000ms for send operation to complete
  </code></pre>
  <p>I expand timeout limit to 3 days, same error occurs still.</p>
  <p>How to deal with that? Thanks~</p>
  <pre><code>dist.init_process_group(
      backend=args.dist_backend, 
      init_method=args.dist_url,
      world_size=args.world_size, rank=args.rank,
      timeout=datetime.timedelta(days=3)
  )
  </code></pre>