title: Using MPI with two RaspberryPi
body: <p>I am trying to make a 'dual core' RaspberryPi for a project I am working on. I had followed this tutorial <a href="http://www.southampton.ac.uk/~sjc/raspberrypi/pi_supercomputer_southampton_web.pdf" rel="nofollow">by Simon Cox</a>. Unfortunately I could not get the two RasPi to talk to each other. (This was using Hydra as the process manager)</p>
  
  <p>After looking more carefully at the MPICH installers guide, <a href="http://www.mpich.org/documentation/guides/" rel="nofollow">which can be found here</a>, I tried to use the -phrase  to pass the passphrase I had created. However I could not find it as part of the hydra commands. So I re-installed with smpd and after many compiling attempts. I configured with:</p>
  
  <p><code>/configure -prefix=/home/pi/mpich-install --with-pm=smpd --with-pmi=smpd</code></p>
  
  <p>I also had to install libbsl-dev to get the MD5 that smpd requires. I also exported the path that the commands mpiexec and mpicc are in. After setting the passphrase I copied the image to a second SD card and put it in a second RasPi. I then set up the passphrase using ssh-keygen.</p>
  
  <p>I was able to run the cpi program on the master Pi and the slave Pi individually but when I tried to run multiple processes on both at the same time I got the error</p>
  
  <p><code>Fatal error in MPI_Init: Other MPI error, error stack:</code>
  <code>MPIR_Init``_thread(392).................:</code>
  <code>MPID_Init(139)........................: channel initialization failed</code>
  <code>MPIDI_CH3_Init(38)....................:</code>
  <code>MPID_nem_init(196)....................:</code>
  <code>MPIDI_CH3I_Seg_commit(366)............:</code>
  <code>MPIU_SHMW_Hnd_deserialize(324)........:</code>
  <code>MPIU_SHMW_Seg_open(863)...............:</code>
  <code>MPIU_SHMW_Seg_create_attach_templ(637): open failed - No such file or directory</code></p>
  
  <p>Can someone please suggest how I can either fix this problem or get the RaspberryPis to communicate using MPICH?</p>
  
  <p>Thanks
  E.Lee</p>