title: mpiexec was unable to launch the specified application (Raspberry pi)
body: <p>I get the same error for each of the 3 following commands.   is my ip address from ifconfig.  Any ideas on what is going wrong?  It worked fine last night.</p>
  
  <pre><code>mpiexec -f machinefile -n &lt;number&gt; hostname
  mpiexec -f machinefile –n 1 hostname
  mpiexec -f machinefile -n 2 ~/mpich_build/examples/cpi
  --------------------------------------------------------------------------
  mpiexec was unable to launch the specified application as it could not find an executable:
  
  Executable: -f
  Node: raspberrypi
  
  while attempting to start process rank 0.
  --------------------------------------------------------------------------
  </code></pre>
  
  <p>I'm following the tutorial from <a href="http://www.southampton.ac.uk/~sjc/raspberrypi/pi_supercomputer_southampton.htm" rel="nofollow">http://www.southampton.ac.uk/~sjc/raspberrypi/pi_supercomputer_southampton.htm</a></p>