Documentation of migrate
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Function Synopsis
[Chrom, ObjV] = migrate(Chrom, SUBPOP, MigOpt, ObjV, Rank);
Help text
MIGRATion of individuals between subpopulations
This function performs migration of individuals.
The structure of the subpopulations can be chosen between:
- complete net structure (unrestricted migration)
- neighbourhood structure
- ring structure
The selection of the individuals for migration can be chosen between:
- uniform at random selection
- fitness-based selection
The insertion of migrants is done uniform at random.
For fitness-based migration (best individuals migrate) the fitness
values/ranking of the population (Rank) is needed. If omitted or
empty single objective scaling using the first column of the objective
values (ObjV) is assumed.
If the objective values of the population (ObjV) are input parameter
and ObjV is output parameter the objective values are copied,
according to the migration of individuals, saving the recomputation
of the objective values for the whole population.
The function can handle multiple objective values per individual.
Different size of every subpopulation is supported.
Syntax: [Chrom, ObjV] = migrate(Chrom, SUBPOP, MigOpt, ObjV, Rank)
Input parameters:
Chrom - Matrix containing the individuals of the current
population. Each row corresponds to one individual.
SUBPOP - (optional) Vector/scalar containing number of individuals
per subpopulation/number of subpopulations
if omitted or NaN, 1 subpopulation is assumed
MigOpt - (optional) Vector containing migration paremeters
MigOpt(1): MIGR - Rate of individuals to be migrated per
subpopulation (% of subpopulation)
if omitted or NaN, 0.2 (20%) is assumed
MigOpt(2): Select - number indicating the selection method
of replacing individuals
0 - uniform selection
1 - fitness-based selection (best individuals migrate)
if omitted or NaN, 0 is assumed
MigOpt(3): Structure - number indicating the structure
of the subpopulations for migration
0 - net structure (unconstrained migration)
1 - neighbourhood structure
2 - ring structure
if omitted or NaN, 0 is assumed
ObjV - (optional) Column vector or matrix containing the objective values
of the individuals in the current population,
if Rank is omitted, first column is used for fitness-based migration,
saves recalculation of objective values for population
Rank - (optional) Column vector containing the fitness values (obtained
by ranking) of the individuals in the current population,
best individual has highest value,
if omitted or empty, single objective scaling using first column
of ObjV is assumed
Output parameters:
Chrom - Matrix containing the individuals of the current
population after migration.
ObjV - if ObjV is input parameter, than column vector containing
the objective values of the individuals of the current
generation after migration.
See also: geamain, mutate, recombin, selection
Cross-Reference Information
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This document is part of
version 3.8 of the
GEATbx: Genetic and Evolutionary Algorithm Toolbox for use with Matlab -
www.geatbx.com.
The Genetic and Evolutionary Algorithm Toolbox is
not public domain.
© 1994-2006 Hartmut Pohlheim, All Rights Reserved,
(support@geatbx.com).