.. _method-moga-fitness_type-domination_count:

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domination_count
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Rank each member by the number of members that dominate it


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**Specification**

- *Alias:* None

- *Arguments:* None


**Description**


The ``fitness_type``: ``domination_count`` has been specifically
designed to avoid problems with aggregating and scaling objective
function values and transforming them into a single objective.

Instead, the ``domination_count`` fitness assessor works by ordering
population members by the negative of the number of designs that
dominate them. The values are negated in keeping with the convention
that higher fitness is better.

The ``layer_rank`` fitness assessor works by assigning all
non-dominated designs a layer of 0, then from what remains, assigning
all the non-dominated a layer of 1, and so on until all designs have
been assigned a layer. Again, the values are negated for the
higher-is-better fitness convention.

Use of the ``below_limit`` selector with the ``domination_count``
fitness assessor has the effect of keeping all designs that are
dominated by fewer then a limiting number of other designs subject to
the shrinkage limit.

Using it with the ``layer_rank`` fitness assessor has the effect of
keeping all those designs whose layer is below a certain threshold
again subject to the shrinkage limit.


