brkga_mp_ipr.enums module

class brkga_mp_ipr.enums.BiasFunctionType[source]

Bases: brkga_mp_ipr.enums.ParsingEnum

Specifies a bias function when choosing parents to mating. This function substitutes the \(\rho\) (rho) parameter from the original BRKGA. For a given rank \(r\), we have the following functions:

  • CONSTANT: 1 / number of parents for mating (all individuals have the same probability)

  • CUBIC: \(r^{-3}\)

  • EXPONENTIAL: \(\epsilon^{-r}\)

  • LINEAR: \(1 / r\)

  • LOGINVERSE: \(1 / \log(r + 1)\)

  • QUADRATIC: \(r^{-2}\)

CONSTANT = 0
CUBIC = 1
CUSTOM = 6
EXPONENTIAL = 2
LINEAR = 3
LOGINVERSE = 4
QUADRATIC = 5
class brkga_mp_ipr.enums.ParsingEnum[source]

Bases: enum.Enum

Implements a base Enum class that returns an Enum object from a string (case insensitive).

class brkga_mp_ipr.enums.PathRelinkingResult[source]

Bases: enum.Flag

Specifies the result type/status of path relink procedure:

  • TOO_HOMOGENEOUS: the chromosomes among the populations are too homogeneous and the path relink will not generate improveded solutions.

  • NO_IMPROVEMENT: path relink was done but no improveded solution was found.

  • ELITE_IMPROVEMENT: an improved solution among the elite set was found, but the best solution was not improved.

  • BEST_IMPROVEMENT: the best solution was improved.

BEST_IMPROVEMENT = 7
ELITE_IMPROVEMENT = 3
NO_IMPROVEMENT = 1
TOO_HOMOGENEOUS = 0
class brkga_mp_ipr.enums.PathRelinkingSelection[source]

Bases: brkga_mp_ipr.enums.ParsingEnum

Specifies which individuals used to build the path:

  • BESTSOLUTION: selects, in the order, the best solution of each population.

  • RANDOMELITE: chooses uniformly random solutions from the elite sets.

BESTSOLUTION = 0
RANDOMELITE = 1
class brkga_mp_ipr.enums.PathRelinkingType[source]

Bases: brkga_mp_ipr.enums.ParsingEnum

Specifies type of path relinking:

  • DIRECT: changes each key for the correspondent in the other chromosome.

  • PERMUTATION: switches the order of a key for that in the other chromosome.

DIRECT = 0
PERMUTATION = 1
class brkga_mp_ipr.enums.Sense[source]

Bases: brkga_mp_ipr.enums.ParsingEnum

Tells the algorithm either to MINIMIZE or MAXIMIZE the objective function.

MAXIMIZE = 1
MINIMIZE = 0
class brkga_mp_ipr.enums.ShakingType[source]

Bases: brkga_mp_ipr.enums.ParsingEnum

Specifies the type of shaking to be performed.

  • CHANGE: applies the following perturbations:

    1. Inverts the value of a random chosen, i.e., from \(value\) to \(1 - value\);

    2. Assigns a random value to a random key.

  • SWAP: applies two swap perturbations:

    1. Swaps the values of a randomly chosen key \(i\) and its neighbor \(i + 1\);

    2. Swaps values of two randomly chosen keys.

CHANGE = 0
SWAP = 1