title: mpirun actual number of processors used
body: <p>I am starting programming on an OpenMPI managed cluster.
  I use the following command to run my executable:</p>
  
  <pre><code>mpirun -np 32 file
  </code></pre>
  
  <p>Now what I understand is that 32 specifies the number of processes that should be created. They may be created on the same processor. Am I right?</p>
  
  <p>I am noticing increasing time for execution with increase in the number of processes. Could the above be a reason for this?</p>
  
  <p>How do I find out the execution and scheduling policy of the cluster?</p>
  
  <p>Is it correct to assume that typically the cluster I am working on will have many processes running on each node just as they run on my PC. </p>