title: Figuring out the number of processors for using openmpi
body: <p>I have compiled a weather forecasting software with openmpi in double precision on Ubuntu 14.04  and Intel ifort compiler. However I am not able to figure out few issues. I need to figure out the number of processors I need to send to mpirun. This is the output of lscpu            </p>
  
  <pre><code>x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Byte Order:            Little Endian
  CPU(s):                4
  On-line CPU(s) list:   0-3
  Thread(s) per core:    2
  Core(s) per socket:    2
  Socket(s):             1
  NUMA node(s):          1
  Vendor ID:             GenuineIntel
  CPU family:            6
  Model:                 60
  Stepping:              3
  CPU MHz:               800.000
  BogoMIPS:              6784.93
  Virtualization:        VT-x
  L1d cache:             32K
  L1i cache:             32K
  L2 cache:              256K
  L3 cache:              3072K
  NUMA node0 CPU(s):     0-3output of lscpu
  </code></pre>
  
  <p>This is the command that I am using to run my software
  mpirun -np 4 aaa. But When I do this I get these errors - </p>
  
  <pre><code>MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD 
  with errorcode 1001.
  
  NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
  You may or may not see output from other processes, depending on
  exactly when Open MPI kills them.
  </code></pre>
  
  <p>When I set np to 1 it runs successfully but does not use the CPU completely. CPU usage varies from 3% to 35% but the memory usage is almost 100% and the system freezes for about ten minutes and exits with the error message</p>
  
  <p>forrtl severe(41) insufficient virtual memory. </p>
  
  <p>I have run WRF (the software associated with this question is not WRF) with multiple semaphores and I have not experienced any speed or memory issues. 
  I could recompile to single precision but before I do that I want to be able to figure out the number of cores(processors) to be sent to mpirun. </p>