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# Distribution of tasks across multiple CPUs using `mpi`

Warning

This example requires execution on 2 CPUs. It can be run using: `$ mpirun -n 2 python path/to/parallel_tasks.rst`

All I’m doing here is illustrating the use of `parallel.map` with the simplest example I could come up with. I create a list which will have an integer appended to it – hardly useful, but hopefully demonstrates how a series of data can be mapped onto a function in parallel. In this case, the data is just a list of numbers.

    >>> from cogent.util import parallel
    >>> passed_indices = []
    >>> series = range(20)
    >>> result = parallel.map(passed_indices.append, series)
    >>> assert passed_indices == range(0,20,2) or passed_indices == range(1,20,2)

The result is either the list of even numbers up to (but not including) 20 or the list of odd numbers.