Running

• MPI

  The Message Passing Interface (MPI) is a standard interface for parallel programming. MPI is good, because it means you only have to learn one standard for writing parallel programs across many types of machines from many vendors. However, it is not exactly portable, since certain semantics are left undefined in the standard. Furthermore, performance is not portable with MPI -- what works for one cluster with Myrinet may not work well on a shared memory machine. MPI has bindings for C, C++, and Fortran.

  The best way to get started with MPI is by example. There are several tutorials available on line. This site has a listing of several. An excellent tutorial can be found a the NCSA. More general documentation can be found at the main site for MPI. There are also several books written about MPI.

• MPICH

  MPICH is an MPI implementation.

  Here is an example of using mpich to call a program called factor which has a source file mpich.c:

  [bargle@brood01 factor]$ /opt/topspin/mpi/mpich/bin/mpicc -lm -o factor-mpich factor.c
  [bargle@brood01 factor]$ 
  		      

  We submit the following file.

  #!/bin/bash
  # Special PBS control comments
  #PBS -l nodes=4,walltime=60
  
  # Set up the path
  PATH=/opt/topspin/mpi/mpich/bin/mpicc:$PATH
  export PATH
  cd $HOME/.src/factor
  
  # Run the program
  mpirun -np $( wc -l < $PBS_NODEFILE ) -hostfile $PBS_NODEFILE factor-mpich 2305843009213693953
  		      

  The resulting output is:

  Warning: no access to tty (Bad file descriptor).
  Thus no job control in this shell.
  Prime factors of 2305843009213693953:
  3
  768614336404564651