Selector Base Class

Base class representing selection operations, inheriting from MiesOperator.

A Selector gets a table of individuals as input, along with information on the individuals' performance values and the number of individuals to select, and returns a vector of integers indicating which individuals were selected.

Selection operations are performed in ES algorithms to facilitate concentration towards individuals that perform well with regard to the fitness measure.

Fitness values are always maximized, both in single- and multi-criterion optimization.

Unlike most other operator types inheriting from MiesOperator, the $operate() function has three arguments, which are passed on to $.select()

• values :: data.frame
  Individuals to operate on. Must pass the check of the Param given in the last $prime() call and may not have any missing components.

• fitnesses :: numeric | matrix
  Fitnesses for each individual given in values. If this is a numeric, then its length must be equal to the number of rows in values. If this is a matrix, if number of rows must be equal to the number of rows in values, and it must have one column when doing single-crit optimization and one column each for each "criterion" when doing multi-crit optimization.
  The fitnesses-value passed on to $.select() is always a matrix.

• n_select :: integer(1)
  Number of individuals to select. Some Selectors select individuals with replacement, for which this value may be greater than the number of rows in values.

• group_size :: integer
  Sampling group size hint, indicating that the caller would prefer there to not be any duplicates within this group size, e.g. because the Selector is called to select individuals to be given to a Recombinator with a certain n_indivs_in, or because it is called as a survival_selector in mies_survival_comma() or mies_survival_plus(). The Selector may or may not ignore this value, however. This may possibly happen because of certain configuration parameters, or because the input size is too small.
  Must either be a scalar value or sum up to n_select. Must be non-negative. A scalar value of 0 is interpreted the same as 1.
  If not given, this value defaults to 1.

The return value for an operation will be a numeric vector of integer values of length n_select indexing the individuals that were selected. Some Selectors select individuals with replacement, for which the return value may contain indices more than once.

Inheriting

Selector is an abstract base class and should be inherited from. Inheriting classes should implement the private $.select() function. The user of the object calls $operate(), and the arguments are passed on to private $.select() after checking that the operator is primed, that the values argument conforms to the primed domain and that other values match. Typically, the $initialize() function should also be overloaded, and optionally the $prime() function; they should call their super equivalents.

See also

Other base classes: Filtor, FiltorSurrogate, MiesOperator, Mutator, MutatorDiscrete, MutatorNumeric, OperatorCombination, Recombinator, RecombinatorPair, Scalor, SelectorScalar

Other selectors: SelectorScalar, dict_selectors_best, dict_selectors_maybe, dict_selectors_null, dict_selectors_proxy, dict_selectors_random, dict_selectors_sequential, dict_selectors_tournament

Super class

miesmuschel::MiesOperator -> Selector

Active bindings

supported

(character)
Optimization supported by this Selector, can be "single-crit", "multi-crit", or both.

Methods

Public methods

• Selector$new()

• Selector$clone()

Inherited methods

• miesmuschel::MiesOperator$help()
• miesmuschel::MiesOperator$operate()
• miesmuschel::MiesOperator$prime()
• miesmuschel::MiesOperator$print()
• miesmuschel::MiesOperator$repr()

---

Method new()

Initialize base class components of the Selector.

Usage

Selector$new(
  is_deterministic = FALSE,
  param_classes = c("ParamLgl", "ParamInt", "ParamDbl", "ParamFct"),
  param_set = ps(),
  supported = c("single-crit", "multi-crit"),
  packages = character(0),
  dict_entry = NULL,
  own_param_set = quote(self$param_set)
)

Arguments

is_deterministic

(logical(1))
Whether the Selector is deterministic. Setting this to TRUE adds a configuration parameter shuffle_selection (initialized to TRUE) that causes the selection to be shuffled.

param_classes

(character)
Classes of parameters that the operator can handle. May contain any of "ParamLgl", "ParamInt", "ParamDbl", "ParamFct". Default is all of them.
The $param_classes field will reflect this value.

param_set

(ParamSet | list of expression)
Strategy parameters of the operator. This should be created by the subclass and given to super$initialize(). If this is a ParamSet, it is used as the MiesOperator's ParamSet directly. Otherwise it must be a list of expressions e.g. created by alist() that evaluate to ParamSets, possibly referencing self and private. These ParamSet are then combined using a ParamSetCollection. Default is the empty ParamSet.
The $param_set field will reflect this value.

supported

(character)
Subset of "single-crit" and "multi-crit", indicating wether single and / or multi-criterion optimization is supported. Default both of them.
The $supported field will reflect this value.

packages

(character) Packages that need to be loaded for the operator to function. This should be declared so these packages can be loaded when operators run on parallel instances. Default is character(0).
The $packages field will reflect this values.

dict_entry

(character(1) | NULL)
Key of the class inside the Dictionary (usually one of dict_mutators, dict_recombinators, dict_selectors), where it can be retrieved using a short access function. May be NULL if the operator is not entered in a dictionary.
The $dict_entry field will reflect this value.

own_param_set

(language)
An expression that evaluates to a ParamSet indicating the configuration parameters that are entirely owned by this operator class (and not proxied from a construction argument object). This should be quote(self$param_set) (the default) when the param_set argument is not a list of expressions.

---

Method clone()

The objects of this class are cloneable with this method.

Usage

Selector$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.