readme.parallel

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Parallel version of XOOPIC


XOOPIC uses the MPI libraries to implement parallel computation.

You must compile and install the MPI libraries before you can 
compile and install a parallel version of XOOPIC.

1)  To compile XOOPIC with MPI:

    Read the file README.INSTALL.  You will need to run
    configure with special options indicating that you are
    using MPI:  in addition to all the other options, you
    will have give options like:
    ./configure --enable-MPI 

    If the configure script cannot find mpiCC, then you must specify
    the location of your MPI compiler, for example if mpiCC is in
    /usr/local/mympi-location/bin/ then use:
    ./configure --enable-MPI --with-MPICXX=/usr/local/mympi-location/bin/mpiCC

    This will tell XOOPIC that it is to compile with parallel
    computation support, and where to find the mpi compiler.

2)  After you've successfully run configure, compile xoopic.

3)  Run xoopic using mpirun: (for example:)
    mpirun -np 2 xoopic -i input/default.inp



Notes and gotcha's of parallel XOOPIC.

1)  Use only uniform meshes.  
2)  It's safer to define boundaries in terms of physical coordinates
    (A1,A2,B1,B2) rather than grid coordinates.  
3)  Electrostatic will NOT work!  No parallel poisson solve has been done.
4)  Particles will see a discontinuity in B3 (3rd component of magnetic field)
    when they cross from one spatial region into another.
5)  Divergence cleaning and Marder correction will NOT work. 
6)  Boltzmann electrons will NOT work.
7)  There's no dynamic load balancing.  Scalability is therefore limited,
    except on problems which naturally parallelize well.
8)  Performance will also suffer if each partition is too small--if 
    computation inside a partition takes less time than communication 
    between partitions, your performance will go down instead of up with
    number of CPU's.
9)  Periodic boundaries will NOT work.