.. _method-soga-replacement_type-unique_roulette_wheel:

"""""""""""""""""""""
unique_roulette_wheel
"""""""""""""""""""""


Replace population


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**Specification**

- *Alias:* None

- *Arguments:* None


**Description**


Replace the population with members selected to continue in the next
generation.  The pool of potential members is the current population
and the current set of offspring.  The ``replacement_type`` of
``roulette_wheel`` or ``unique_roulette_wheel`` may be used either with
MOGA or SOGA problems however they are not recommended for use with
MOGA.  Given that the only two fitness assessors for MOGA are the
``layer_rank`` and ``domination_count``, the recommended selector is the
``below_limit`` selector.  The ``below_limit`` replacement will only keep
designs that are dominated by fewer than a limiting number of other
designs.  The ``replacement_type`` of ``favor_feasible`` is specific to
a SOGA.  This replacement operator will always prefer a more feasible
design to a less feasible one.  Beyond that, it favors solutions based
on an assigned fitness value which must have been installed by the
weighted sum only fitness assessor (see the discussion below).


