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====== MPI Parallelization ======
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To enable MPI parallelization in //potfit// you have to add the ''--enable-mpi'' switch to the ''./waf configure'' command:

<code>./waf configure -i pair -m apot --enable-mpi</code>

How to run a parallel version of //potfit// is described [[running:main|here]]

===  How does the parallel code work?  ===

The parallelization of //potfit// is a rather simple one. The configurations are distributed evenly among all available processes. This means, that if you have N configurations in your configuration file,
it does not make sense to use more than N processes (also //potfit// will issue a warning if this is the case).

All the work of the optimization algorithms is done by the first process, all other processes will only be doing force calculations. After the initialization is complete and the configurations have been distributed to all
available processes, the main process will determine new parameters, based on the optimization method, and broadcast them to all other processes. Every process will then calculate the potential from these parameters and the forces, energies, stresses, .... for its configurations. After this is finished, the results will be sent to the main process, who determines how to continue the optimization. The other processes wait for the next set of parameters to be transmitted by the main process.

Even though this is a very basic parallelization, it is rather efficient for //potfit//. Profiling runs have shown that //potfit// spends more than 95% of the computational time in the force routine, calculating forces, energies and stresses.