title: Open MPI stuck on an older version
body: <p>I'm building a Raspberry Pi cluster and am using Open MPI to do some parallel processing... I was able to get it up and running with my Raspberry Pi 3 and a few Pi 1s, but when I tried to add another Pi 3 I started getting some errors (Error: unknown option "--hnp-topo-sig")</p>
  
  <p>It's possible that the problem is because the versions of mpi between both my pis are different - my first pi 3 has version 2.0.2 while the other has 1.6.5, which is odd considering I only installed it on that pi today and on the first pi about a week ago. </p>
  
  <p>I've tried sudo apt-get update and upgrade, but my pi keeps telling me that everything is up to date, even though it doesn't seem like it is. So my question is this - how can I update my open mpi to a newer version so I can run my files? Thanks in advance!</p>