53 lines
2.7 KiB
Python
53 lines
2.7 KiB
Python
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from __future__ import division
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def migRing(populations, k, selection, replacement=None, migarray=None):
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"""Perform a ring migration between the *populations*. The migration first
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select *k* emigrants from each population using the specified *selection*
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operator and then replace *k* individuals from the associated population
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in the *migarray* by the emigrants. If no *replacement* operator is
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specified, the immigrants will replace the emigrants of the population,
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otherwise, the immigrants will replace the individuals selected by the
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*replacement* operator. The migration array, if provided, shall contain
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each population's index once and only once. If no migration array is
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provided, it defaults to a serial ring migration (1 -- 2 -- ... -- n --
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1). Selection and replacement function are called using the signature
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``selection(populations[i], k)`` and ``replacement(populations[i], k)``.
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It is important to note that the replacement strategy must select *k*
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**different** individuals. For example, using a traditional tournament for
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replacement strategy will thus give undesirable effects, two individuals
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will most likely try to enter the same slot.
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:param populations: A list of (sub-)populations on which to operate
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migration.
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:param k: The number of individuals to migrate.
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:param selection: The function to use for selection.
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:param replacement: The function to use to select which individuals will
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be replaced. If :obj:`None` (default) the individuals
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that leave the population are directly replaced.
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:param migarray: A list of indices indicating where the individuals from
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a particular position in the list goes. This defaults
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to a ring migration.
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"""
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nbr_demes = len(populations)
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if migarray is None:
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migarray = range(1, nbr_demes) + [0]
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immigrants = [[] for i in xrange(nbr_demes)]
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emigrants = [[] for i in xrange(nbr_demes)]
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for from_deme in xrange(nbr_demes):
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emigrants[from_deme].extend(selection(populations[from_deme], k))
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if replacement is None:
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# If no replacement strategy is selected, replace those who migrate
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immigrants[from_deme] = emigrants[from_deme]
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else:
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# Else select those who will be replaced
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immigrants[from_deme].extend(replacement(populations[from_deme], k))
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for from_deme, to_deme in enumerate(migarray):
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for i, immigrant in enumerate(immigrants[to_deme]):
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indx = populations[to_deme].index(immigrant)
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populations[to_deme][indx] = emigrants[from_deme][i]
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__all__ = ['migRing']
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