title: OpenMPI vs OpenMP execution efficiency
body: <p>I've been studying the efficiency of parallelizing Dijkstra Algorithm using both <code>OpenMPI</code> and <code>OpenMP</code>. In fact, when I use OpenMP, the execution time appears to be <strong>higher</strong> than using OpenMPI which is a bit strange to me since as far as I know threads are supposed to be faster than processes. OpenMPI creates a process for each execution while OpenMP creates threads under each process execution. My question is: Is my finding implementation dependent? In other word, can we always say parallelizing with OpenMP cannot be always faster than OpenMPI since it is an implementation dependent?</p>
  
  <p>Thank you.</p>