metaheuristic_designer.encodings.sigmoid_encoding module

Encoding that applies a sigmoid function to enable continuous operators on binary problems.

class SigmoidEncoding(as_probability=True, threshold=0.5, **kwargs)

Bases: Encoding

Encoding that maps binary solutions to continuous values via a sigmoid.

The encoding applies \(\sigma(x) = 1 / (1 + e^{-x})\) pointwise. During encoding, the logit function is applied to the probability parameter (producing real numbers). During decoding, the sigmoid is applied again. This allows real-valued operators (e.g., Gaussian mutation) to be used on binary problems.

Parameters:

as_probabilitybool, optional

If True (default), each component is returned as a probability in (0, 1). If False, the probability is thresholded to produce a hard 0/1 value.

thresholdfloat, optional

Threshold used when as_probability=False. Must be in (0, 1). Default is 0.5.

**kwargs

Forwarded to Encoding.

Attributes:

params

Access parameter values by attribute-style lookup.

Parameters:

• as_probability (bool)

• threshold (float)

Methods

decode(population)	Decodes a population matrix into a list/array of solutions.
encode(solutions)	Encodes a list of solutions to our problem to an population matrix.
gather_params()	Overridable thin wrapper around get_params
get_params()	Return a copy of the current parameter dictionary.
store_kwargs([progress])	Store keyword arguments and evaluate them at the given progress.
update(progress)	Re-evaluate all stored parameters at the current progress.
update_kwargs([progress])	Add or replace parameters and immediately evaluate them.

get_state

encode(solutions)

Encodes a list of solutions to our problem to an population matrix.

Return type:

ndarray[tuple[int, int], floating] | ndarray[tuple[int, int], integer] | ndarray[tuple[int, int], uint8 | bool]

Parameters:

solutions: Iterable

Solutions that should be encoded.

Returns:

population: ndarray

Population array.

Parameters:

solutions (Iterable)

decode(population)

Decodes a population matrix into a list/array of solutions.

Return type:

Iterable

Parameters:

population: ndarray

Population that should be decoded.

Returns:

solutions: Iterable

List/array of solutions.

Parameters:

population (ndarray[tuple[int, int], floating] | ndarray[tuple[int, int], integer] | ndarray[tuple[int, int], uint8 | bool])