def __init__(self):

pass

def random_mutation(self, offspring):

"""

# If the mutation values are selected from the mutation space, the attribute 'gene_space' is not None. Otherwise, it is None.

# When the 'mutation_probability' parameter exists (i.e. not None), then it is used in the mutation. Otherwise, the 'mutation_num_genes' parameter is used.

if self.mutation_probability is None:

# When the 'mutation_probability' parameter does not exist (i.e. None), then the parameter 'mutation_num_genes' is used in the mutation.

if not (self.gene_space is None):

# When the attribute 'gene_space' exists (i.e. not None), the mutation values are selected randomly from the space of values of each gene.

offspring = self.mutation_by_space(offspring)

else:

offspring = self.mutation_randomly(offspring)

else:

# When the 'mutation_probability' parameter exists (i.e. not None), then it is used in the mutation.

if not (self.gene_space is None):

# When the attribute 'gene_space' exists (i.e. not None), the mutation values are selected from the space of values of each gene.

offspring = self.mutation_probs_by_space(offspring)

else:

offspring = self.mutation_probs_randomly(offspring)

return offspring

def mutation_by_space(self, offspring):

"""

# For each offspring, a value from the gene space is selected randomly and assigned to the selected mutated gene.

for offspring_idx in range(offspring.shape[0]):

mutation_indices = numpy.array(self.python_random_generator.sample(range(0, self.num_genes), self.mutation_num_genes))

swapped_genes = set()

for gene_idx in mutation_indices:

if gene_idx in swapped_genes:

continue

value_from_space = self.mutation_process_gene_value(solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

if self.allow_duplicate_genes == False and value_from_space == offspring[offspring_idx, gene_idx]:

# No value of the gene space is free (e.g. a permutation): swap the gene with another one instead.

offspring[offspring_idx] = self.swap_gene_by_space(solution=offspring[offspring_idx],

gene_idx=gene_idx,

swapped_genes=swapped_genes)

continue

offspring[offspring_idx, gene_idx] = value_from_space

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def mutation_probs_by_space(self, offspring):

"""

# For each offspring, a value from the gene space is selected randomly and assigned to the selected mutated gene.

for offspring_idx in range(offspring.shape[0]):

probs = self.numpy_random_generator.random(size=offspring.shape[1])

swapped_genes = set()

for gene_idx in range(offspring.shape[1]):

if gene_idx in swapped_genes:

continue

if probs[gene_idx] < self.mutation_probability:

value_from_space = self.mutation_process_gene_value(solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

if self.allow_duplicate_genes == False and value_from_space == offspring[offspring_idx, gene_idx]:

# No value of the gene space is free (e.g. a permutation): swap the gene with another one instead.

offspring[offspring_idx] = self.swap_gene_by_space(solution=offspring[offspring_idx],

gene_idx=gene_idx,

swapped_genes=swapped_genes)

continue

# Assigning the selected value from the space to the gene.

offspring[offspring_idx, gene_idx] = value_from_space

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def mutation_process_gene_value(self,

solution,

gene_idx,

range_min=None,

range_max=None,

sample_size=100):

"""

# Check if the gene has a constraint.

if self.gene_constraint and self.gene_constraint[gene_idx] is not None:

# Generate values that meet the gene constraint. Select more than 1 value.

# This method: 1) generates or selects the values 2) filters the values according to the constraint.

values = self.get_valid_gene_constraint_values(range_min=range_min,

range_max=range_max,

gene_value=solution[gene_idx],

gene_idx=gene_idx,

mutation_by_replacement=self.mutation_by_replacement,

solution=solution,

sample_size=sample_size)

if values is None:

# No value found that satisfy the constraint.

# Keep the old value.

value_selected = solution[gene_idx]

else:

# Select a value randomly from the list of values satisfying the constraint.

# If size is used with self.numpy_random_generator.choice(), it returns an array even if it has a single value. To return a numeric value, not an array, then return index 0.

value_selected = self.numpy_random_generator.choice(values, size=1)[0]

else:

# The gene does not have a constraint. Just select a single value.

value_selected = self.generate_gene_value(range_min=range_min,

range_max=range_max,

gene_value=solution[gene_idx],

gene_idx=gene_idx,

solution=solution,

mutation_by_replacement=self.mutation_by_replacement,

sample_size=1)

# Candidate arrays use NumPy scalar types. Match the declared

# Python or NumPy scalar type before storing the selected value.

dtype = self.get_gene_dtype(gene_idx)[0]

return value_selected if dtype is object else dtype(value_selected)

def swap_gene_by_space(self,

solution,

gene_idx,

swapped_genes=None):

"""

def has_constraint(idx):

return bool(self.gene_constraint and self.gene_constraint[idx] is not None)

if swapped_genes is None:

swapped_genes = set()

if gene_idx in swapped_genes or has_constraint(gene_idx):

return solution

gene_value = solution[gene_idx]

candidates = []

for other_idx, other_value in enumerate(solution):

if (other_idx in swapped_genes or other_value == gene_value

or has_constraint(other_idx)):

continue

try:

new_gene_value = self.change_gene_dtype_and_round(gene_idx, other_value)

new_other_value = self.change_gene_dtype_and_round(other_idx, gene_value)

except (OverflowError, ValueError, TypeError):

# A value that cannot be represented by the destination

# dtype cannot be part of a permutation-preserving swap.

continue

# Preserve the original set of numeric values. In particular,

# casting or rounding must not turn a value into a duplicate.

if (self._gene_value_key(new_gene_value) != self._gene_value_key(other_value)

or self._gene_value_key(new_other_value) != self._gene_value_key(gene_value)):

continue

if (not self.is_gene_value_in_space(gene_idx, new_gene_value, gene_value)

or not self.is_gene_value_in_space(other_idx, new_other_value, other_value)):

continue

# A constraint on a different gene may depend on either

# swapped position. Validate the complete candidate solution.

if self.gene_constraint:

candidate_solution = solution.copy()

candidate_solution[gene_idx] = new_gene_value

candidate_solution[other_idx] = new_other_value

if not self.solution_satisfies_gene_constraints(candidate_solution):

continue

candidates.append((other_idx, new_gene_value, new_other_value))

if len(candidates) > 0:

other_idx, new_gene_value, new_other_value = self.python_random_generator.choice(candidates)

solution[gene_idx] = new_gene_value

solution[other_idx] = new_other_value

swapped_genes.update((gene_idx, other_idx))

return solution

def mutation_randomly(self, offspring):

"""

# Random mutation changes one or more genes in each offspring randomly.

for offspring_idx in range(offspring.shape[0]):

# Return the indices of the genes to mutate.

mutation_indices = numpy.array(self.python_random_generator.sample(range(0, self.num_genes),

self.mutation_num_genes))

for gene_idx in mutation_indices:

range_min, range_max = self.get_random_mutation_range(gene_idx)

# Generate a random value for mutation that meets the gene constraint, if one exists.

random_value = self.mutation_process_gene_value(range_min=range_min,

range_max=range_max,

solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

offspring[offspring_idx, gene_idx] = random_value

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def mutation_probs_randomly(self, offspring):

"""

# Random mutation changes one or more genes in each offspring randomly.

for offspring_idx in range(offspring.shape[0]):

# The mutation probabilities for the current offspring.

probs = self.numpy_random_generator.random(size=offspring.shape[1])

for gene_idx in range(offspring.shape[1]):

range_min, range_max = self.get_random_mutation_range(gene_idx)

# A gene is mutated only if its mutation probability is less than the threshold.

if probs[gene_idx] < self.mutation_probability:

# Generate a random value for mutation that meets the gene constraint, if one exists.

random_value = self.mutation_process_gene_value(range_min=range_min,

range_max=range_max,

solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

offspring[offspring_idx, gene_idx] = random_value

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def polynomial_mutation(self, offspring):

"""

eta = float(self.polynomial_mutation_eta)

eta_plus_one = eta + 1.0

for solution_index, solution in enumerate(offspring):

original = solution.copy()

if self.mutation_probability is not None or not self.mutation_control_explicitly_set:

probability = self.mutation_probability if self.mutation_probability is not None else 1.0 / self.num_genes

gene_indices = (index for index in range(self.num_genes) if self.numpy_random_generator.random() < probability)

else:

gene_indices = self.select_mutation_gene_indices()

selected_any_gene = False

for gene_index in gene_indices:

selected_any_gene = True

if self.is_categorical_gene(gene_index):

# A categorical value has no neighbors on a number line,

# so pick one of the other allowed values at random.

solution[gene_index] = self.pick_other_categorical_value(gene_index, solution[gene_index])

continue

lower, upper = map(float, self.get_bounded_operator_gene_range(gene_index))

if upper - lower < 1e-14:

solution[gene_index] = self.convert_bounded_operator_gene_value(gene_index, lower)

continue

value = float(numpy.clip(solution[gene_index], lower, upper))

delta_lower = (value - lower) / (upper - lower)

delta_upper = (upper - value) / (upper - lower)

quantile = self.numpy_random_generator.random()

if quantile <= 0.5:

distance = 1.0 - delta_lower

spread = 2.0 * quantile + (1.0 - 2.0 * quantile) * pow(distance, eta_plus_one)

change = pow(spread, 1.0 / eta_plus_one) - 1.0

else:

distance = 1.0 - delta_upper

spread = 2.0 * (1.0 - quantile) + 2.0 * (quantile - 0.5) * pow(distance, eta_plus_one)

change = 1.0 - pow(spread, 1.0 / eta_plus_one)

new_value = numpy.clip(value + change * (upper - lower), lower, upper)

solution[gene_index] = self.convert_bounded_operator_gene_value(gene_index, new_value)

if selected_any_gene:

offspring[solution_index] = self.prepare_bounded_operator_solution(original, solution)

return offspring

def select_mutation_gene_indices(self):

"""Select eligible genes using the active probability or gene count."""

if self.mutation_probability is not None:

return numpy.where(self.numpy_random_generator.random(self.num_genes) < self.mutation_probability)[0]

return numpy.asarray(self.python_random_generator.sample(range(self.num_genes), self.mutation_num_genes), dtype=int)

def swap_mutation(self, offspring):

"""Swap a compatible pair of eligible genes in each offspring.

return self._apply_permutation_mutation(offspring, 'swap')

def inversion_mutation(self, offspring):

"""Reverse eligible genes, keeping changes that satisfy destination rules."""

return self._apply_permutation_mutation(offspring, 'inversion')

def scramble_mutation(self, offspring):

"""Shuffle eligible genes, keeping changes that satisfy destination rules."""

return self._apply_permutation_mutation(offspring, 'scramble')

def _apply_permutation_mutation(self, offspring, mutation_type):

"""Share gene selection and complete-solution validation for permutations.

if self.num_genes < 2:

return offspring

for solution_index, solution in enumerate(offspring):

if self.mutation_control_explicitly_set:

eligible = numpy.sort(self.select_mutation_gene_indices())

elif mutation_type == 'swap':

eligible = numpy.arange(self.num_genes)

else:

start = self.numpy_random_generator.randint(low=0, high=int(numpy.ceil(self.num_genes / 2 + 1)), size=1)[0]

eligible = numpy.arange(start, start + self.num_genes // 2)

if len(eligible) < 2:

continue

original = solution.copy()

grouped_swap = mutation_type == 'swap' and self.mutation_control_explicitly_set and len(eligible) > 2

if mutation_type == 'swap' and not grouped_swap:

first, second = self.numpy_random_generator.choice(eligible, size=2, replace=False)

candidate_pairs = [(first, second)]

# Iterate remaining pairs lazily only if the initial swap

# fails, rather than allocating a quadratic pair array.

candidates = chain(candidate_pairs, combinations(eligible.tolist(), 2))

elif mutation_type == 'inversion':

candidates = chain([(0, len(eligible) - 1)], combinations(range(len(eligible)), 2))

else:

candidates = range(self.sample_size)

for candidate in candidates:

proposed = original.copy()

if grouped_swap:

positions = eligible.copy()

self.numpy_random_generator.shuffle(positions)

for first, second in zip(positions[::2], positions[1::2]):

proposed[first], proposed[second] = original[second], original[first]

elif mutation_type == 'swap':

first, second = candidate

proposed[first], proposed[second] = original[second], original[first]

elif mutation_type == 'inversion':

first, last = candidate

selected = eligible[first:last + 1]

proposed[selected] = original[selected][::-1]

else:

values = original[eligible].copy()

self.numpy_random_generator.shuffle(values)

proposed[eligible] = values

prepared = self.prepare_changed_operator_solution(original, proposed)

if prepared is not None:

offspring[solution_index] = prepared

break

return offspring

def adaptive_mutation_population_fitness(self, offspring):

"""Evaluate the kept solutions and actual offspring before mutation."""

if self.keep_elitism > 0:

parents_to_keep, kept_indices = self.steady_state_selection(

self.last_generation_fitness, num_parents=self.keep_elitism)

elif self.keep_parents == -1:

parents_to_keep = self.last_generation_parents.copy()

kept_indices = self.last_generation_parents_indices

elif self.keep_parents > 0:

parents_to_keep, kept_indices = self.steady_state_selection(

self.last_generation_fitness, num_parents=self.keep_parents)

else:

parents_to_keep = []

kept_indices = []

num_kept = len(parents_to_keep)

temp_population = numpy.empty_like(self.population)

if num_kept:

temp_population[:num_kept] = parents_to_keep

temp_population[num_kept:] = offspring

offspring_indices = list(range(num_kept, len(temp_population)))

offspring_fitness = self._evaluate_fitness(

temp_population, offspring_indices, adaptive=True)

# Offspring can have fractional fitness even when the previous

# population's values were integers. Let NumPy infer the new dtype.

fitness = numpy.array(list(self.last_generation_fitness[kept_indices])

+ offspring_fitness)

return numpy.mean(fitness, axis=0), fitness[num_kept:]

def adaptive_mutation(self, offspring):

"""

if self.mutation_probability is not None and not any(self.mutation_probability):

return offspring

# If the attribute 'gene_space' exists (i.e. not None), then the mutation values are selected from the 'gene_space' parameter according to the space of values of each gene. Otherwise, it is selected randomly based on the 2 parameters 'random_mutation_min_val' and 'random_mutation_max_val'.

# When the 'mutation_probability' parameter exists (i.e. not None), then it is used in the mutation. Otherwise, the 'mutation_num_genes' parameter is used.

if self.mutation_probability is None:

# When the 'mutation_probability' parameter does not exist (i.e. None), then the parameter 'mutation_num_genes' is used in the mutation.

if not (self.gene_space is None):

# When the attribute 'gene_space' exists (i.e. not None), the mutation values are selected randomly from the space of values of each gene.

offspring = self.adaptive_mutation_by_space(offspring)

else:

# When the attribute 'gene_space' does not exist (i.e. None), the mutation values are selected randomly based on the continuous range specified by the 2 attributes 'random_mutation_min_val' and 'random_mutation_max_val'.

offspring = self.adaptive_mutation_randomly(offspring)

else:

# When the 'mutation_probability' parameter exists (i.e. not None), then it is used in the mutation.

if not (self.gene_space is None):

# When the attribute 'gene_space' exists (i.e. not None), the mutation values are selected randomly from the space of values of each gene.

offspring = self.adaptive_mutation_probs_by_space(offspring)

else:

# When the attribute 'gene_space' does not exist (i.e. None), the mutation values are selected randomly based on the continuous range specified by the 2 attributes 'random_mutation_min_val' and 'random_mutation_max_val'.

offspring = self.adaptive_mutation_probs_randomly(offspring)

return offspring

def adaptive_mutation_by_space(self, offspring):

"""

# For each offspring, a value from the gene space is selected randomly and assigned to the selected gene for mutation.

average_fitness, offspring_fitness = self.adaptive_mutation_population_fitness(offspring)

# Adaptive mutation changes one or more genes in each offspring randomly.

# The number of genes to mutate depends on the solution's fitness value.

for offspring_idx in range(offspring.shape[0]):

## TODO Make edits to work with multi-objective optimization.

# Compare the fitness of each offspring to the average fitness of each objective function.

fitness_comparison = offspring_fitness[offspring_idx] < average_fitness

# Check if the problem is single or multi-objective optimization.

if type(fitness_comparison) in [bool, numpy.bool_]:

# Single-objective optimization problem.

if offspring_fitness[offspring_idx] < average_fitness:

adaptive_mutation_num_genes = self.mutation_num_genes[0]

else:

adaptive_mutation_num_genes = self.mutation_num_genes[1]

else:

# Multi-objective optimization problem.

# Get the sum of the pool array (result of comparison).

# True is considered 1 and False is 0.

fitness_comparison_sum = sum(fitness_comparison)

# Check if more than or equal to 50% of the objectives have fitness greater than the average.

# If True, then use the first percentage.

# If False, use the second percentage.

if fitness_comparison_sum >= len(fitness_comparison)/2:

adaptive_mutation_num_genes = self.mutation_num_genes[0]

else:

adaptive_mutation_num_genes = self.mutation_num_genes[1]

mutation_indices = numpy.array(self.python_random_generator.sample(range(0, self.num_genes), adaptive_mutation_num_genes))

swapped_genes = set()

for gene_idx in mutation_indices:

if gene_idx in swapped_genes:

continue

value_from_space = self.mutation_process_gene_value(solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

if self.allow_duplicate_genes == False and value_from_space == offspring[offspring_idx, gene_idx]:

# No value of the gene space is free (e.g. a permutation): swap the gene with another one instead.

offspring[offspring_idx] = self.swap_gene_by_space(solution=offspring[offspring_idx],

gene_idx=gene_idx,

swapped_genes=swapped_genes)

continue

# Assigning the selected value from the space to the gene.

offspring[offspring_idx, gene_idx] = value_from_space

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def adaptive_mutation_randomly(self, offspring):

"""

average_fitness, offspring_fitness = self.adaptive_mutation_population_fitness(offspring)

# Adaptive random mutation changes one or more genes in each offspring randomly.

# The number of genes to mutate depends on the solution's fitness value.

for offspring_idx in range(offspring.shape[0]):

## TODO Make edits to work with multi-objective optimization.

# Compare the fitness of each offspring to the average fitness of each objective function.

fitness_comparison = offspring_fitness[offspring_idx] < average_fitness

# Check if the problem is single or multi-objective optimization.

if type(fitness_comparison) in [bool, numpy.bool_]:

# Single-objective optimization problem.

if fitness_comparison:

adaptive_mutation_num_genes = self.mutation_num_genes[0]

else:

adaptive_mutation_num_genes = self.mutation_num_genes[1]

else:

# Multi-objective optimization problem.

# Get the sum of the pool array (result of comparison).

# True is considered 1 and False is 0.

fitness_comparison_sum = sum(fitness_comparison)

# Check if more than or equal to 50% of the objectives have fitness greater than the average.

# If True, then use the first percentage.

# If False, use the second percentage.

if fitness_comparison_sum >= len(fitness_comparison)/2:

adaptive_mutation_num_genes = self.mutation_num_genes[0]

else:

adaptive_mutation_num_genes = self.mutation_num_genes[1]

mutation_indices = numpy.array(self.python_random_generator.sample(range(0, self.num_genes), adaptive_mutation_num_genes))

for gene_idx in mutation_indices:

range_min, range_max = self.get_random_mutation_range(gene_idx)

# Generate a random value fpr mutation that meet the gene constraint if exists.

random_value = self.mutation_process_gene_value(range_min=range_min,

range_max=range_max,

solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

offspring[offspring_idx, gene_idx] = random_value

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def adaptive_mutation_probs_by_space(self, offspring):

"""

# For each offspring, a value from the gene space is selected randomly and assigned to the selected gene for mutation.

average_fitness, offspring_fitness = self.adaptive_mutation_population_fitness(offspring)

# Adaptive random mutation changes one or more genes in each offspring randomly.

# The probability of mutating a gene depends on the solution's fitness value.

for offspring_idx in range(offspring.shape[0]):

## TODO Make edits to work with multi-objective optimization.

# Compare the fitness of each offspring to the average fitness of each objective function.

fitness_comparison = offspring_fitness[offspring_idx] < average_fitness

# Check if the problem is single or multi-objective optimization.

if type(fitness_comparison) in [bool, numpy.bool_]:

# Single-objective optimization problem.

if offspring_fitness[offspring_idx] < average_fitness:

adaptive_mutation_probability = self.mutation_probability[0]

else:

adaptive_mutation_probability = self.mutation_probability[1]

else:

# Multi-objective optimization problem.

# Get the sum of the pool array (result of comparison).

# True is considered 1 and False is 0.

fitness_comparison_sum = sum(fitness_comparison)

# Check if more than or equal to 50% of the objectives have fitness greater than the average.

# If True, then use the first percentage.

# If False, use the second percentage.

if fitness_comparison_sum >= len(fitness_comparison)/2:

adaptive_mutation_probability = self.mutation_probability[0]

else:

adaptive_mutation_probability = self.mutation_probability[1]

probs = self.numpy_random_generator.random(size=offspring.shape[1])

swapped_genes = set()

for gene_idx in range(offspring.shape[1]):

if gene_idx in swapped_genes:

continue

if probs[gene_idx] < adaptive_mutation_probability:

value_from_space = self.mutation_process_gene_value(solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

if self.allow_duplicate_genes == False and value_from_space == offspring[offspring_idx, gene_idx]:

# No value of the gene space is free (e.g. a permutation): swap the gene with another one instead.

offspring[offspring_idx] = self.swap_gene_by_space(solution=offspring[offspring_idx],

gene_idx=gene_idx,

swapped_genes=swapped_genes)

continue

# Assigning the selected value from the space to the gene.

offspring[offspring_idx, gene_idx] = value_from_space

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])

return offspring

def adaptive_mutation_probs_randomly(self, offspring):

"""

average_fitness, offspring_fitness = self.adaptive_mutation_population_fitness(offspring)

# Adaptive random mutation changes one or more genes in each offspring randomly.

# The probability of mutating a gene depends on the solution's fitness value.

for offspring_idx in range(offspring.shape[0]):

## TODO Make edits to work with multi-objective optimization.

# Compare the fitness of each offspring to the average fitness of each objective function.

fitness_comparison = offspring_fitness[offspring_idx] < average_fitness

# Check if the problem is single or multi-objective optimization.

if type(fitness_comparison) in [bool, numpy.bool_]:

# Single-objective optimization problem.

if offspring_fitness[offspring_idx] < average_fitness:

adaptive_mutation_probability = self.mutation_probability[0]

else:

adaptive_mutation_probability = self.mutation_probability[1]

else:

# Multi-objective optimization problem.

# Get the sum of the pool array (result of comparison).

# True is considered 1 and False is 0.

fitness_comparison_sum = sum(fitness_comparison)

# Check if more than or equal to 50% of the objectives have fitness greater than the average.

# If True, then use the first percentage.

# If False, use the second percentage.

if fitness_comparison_sum >= len(fitness_comparison)/2:

adaptive_mutation_probability = self.mutation_probability[0]

else:

adaptive_mutation_probability = self.mutation_probability[1]

probs = self.numpy_random_generator.random(size=offspring.shape[1])

for gene_idx in range(offspring.shape[1]):

range_min, range_max = self.get_random_mutation_range(gene_idx)

if probs[gene_idx] < adaptive_mutation_probability:

# Generate a random value for mutation that meets the gene constraint, if one exists.

random_value = self.mutation_process_gene_value(range_min=range_min,

range_max=range_max,

solution=offspring[offspring_idx],

gene_idx=gene_idx,

sample_size=self.sample_size)

offspring[offspring_idx, gene_idx] = random_value

if self.allow_duplicate_genes == False:

offspring[offspring_idx], _, _ = self.solve_duplicate_genes(solution=offspring[offspring_idx])