cocoex.Problem : API documentation

Problem instances are usually generated using class Suite.

The main feature of a problem instance is that it is callable, returning the objective function value when called with a candidate solution as input.

It provides other useful properties and methods like dimension, number_of_constraints, observe_with, initial_solution_proposal...

Method	__init__	Undocumented
Method	constraint	return constraint values for `x`.
Method	logger_biobj_feed_solution	Feed the given solution to logger_biobj in order to reconstruct its output.
Method	add_observer	`add_observer(self, observer: Observer)`, see `observe_with`.
Method	observe_with	`observe_with(self, observer: Observer)` attaches an `Observer` instance to this problem.
Method	initial_solution_proposal	return feasible initial solution proposals.
Method	initial_solution	return feasible initial solution
Method	observers	list of observers wrapped around this problem
Method	is_observed	problem `p` is observed `p.is_observed` times.
Method	number_of_variables	Number of variables this problem instance expects as input.
Method	dimension	alias for `number_of_variables` of the input space
Method	number_of_objectives	number of objectives, if equal to 1, call returns a scalar
Method	number_of_constraints	number of constraints
Method	lower_bounds	depending on the test bed, these are not necessarily strict bounds
Method	upper_bounds	depending on the test bed, these are not necessarily strict bounds
Method	evaluations	number of times this `Problem` instance was evaluated
Method	final_target_hit	return 1 if the final target is known and has been hit, 0 otherwise
Method	final_target_fvalue1	Undocumented
Method	best_observed_fvalue1	Undocumented
Method	free	Free the given test problem.
Method	id	ID as string without spaces or weird characters
Method	id_function	function number inferred from `id`
Method	id_instance	instance number inferred from `id`
Method	name	human readible short description with spaces
Method	index	problem index in the benchmark `Suite` of origin
Method	suite	benchmark suite this problem is from
Method	info	human readible info, alias for `str(self)`.
Method	_f0	"inofficial" interface to `self` with target f-value of zero.

def __init__(self):

Undocumented

def constraint(self, x):

return constraint values for x.

By convention, constraints with values <= 0 are satisfied.

def logger_biobj_feed_solution(self, evaluation, y):

Feed the given solution to logger_biobj in order to reconstruct its output.

Return 1 if the given solution updated the archive and 0 otherwise.

Used by preprocessing when updating the .info, .dat and .tdat files with new indicator reference values.

def add_observer(self, observer):

add_observer(self, observer: Observer), see observe_with.

def observe_with(self, observer):

observe_with(self, observer: Observer) attaches an Observer instance to this problem.

Attaching an observer can be considered as wrapping the observer around the problem. For the observer to be finalized, the problem must be free'd (implictly or explicitly).

Return the observed problem self.

Details: observer can be None, in which case nothing is done.

See also: class Observer

def _f0(self, x):

"inofficial" interface to self with target f-value of zero.

def initial_solution_proposal(self, restart_number=None):

return feasible initial solution proposals.

For unconstrained problems, the proposal is different for each consecutive call without argument and for each restart_number and may be different under repeated calls with the same restart_number. self.initial_solution_proposal(0) is the same as self.initial_solution.

Conceptual example:

# given: a suite instance, a budget, and fmin
for problem in suite:
    # restart until budget is (over-)exhausted
    while problem.evaluations < budget and not problem.final_target_hit:
        fmin(problem, problem.initial_solution_proposal())

Details: by default, the first proposal is the domain middle or the (only) known feasible solution. Subsequent proposals are coordinate-wise sampled as the sum of two iid random variates uniformly distributed within the domain boundaries. On the 'bbob' suite their density is 0.2 * (x / 5 + 1) for x in [-5, 0] and 0.2 * (1 - x / 5) for x in [0, 5] and zero otherwise.

@property
def initial_solution(self):

return feasible initial solution

@property
def observers(self):

list of observers wrapped around this problem

@property
def is_observed(self):

problem p is observed p.is_observed times.

See also: the list of observers in property observers.

@property
def number_of_variables(self):

Number of variables this problem instance expects as input.

@property
def dimension(self):

alias for number_of_variables of the input space

@property
def number_of_objectives(self):

number of objectives, if equal to 1, call returns a scalar

@property
def number_of_constraints(self):

number of constraints

@property
def lower_bounds(self):

depending on the test bed, these are not necessarily strict bounds

@property
def upper_bounds(self):

depending on the test bed, these are not necessarily strict bounds

@property
def evaluations(self):

number of times this Problem instance was evaluated

@property
def final_target_hit(self):

return 1 if the final target is known and has been hit, 0 otherwise

@property
def final_target_fvalue1(self):

Undocumented

@property
def best_observed_fvalue1(self):

Undocumented

def free(self, force=False):

Free the given test problem.

Not strictly necessary (unless, possibly, for the observer). free ensures that all files associated with the problem are closed as soon as possible and any memory is freed. After free()ing the problem, all other operations are invalid and will raise an exception.

@property
def id(self):

ID as string without spaces or weird characters

@property
def id_function(self):

function number inferred from id

@property
def id_instance(self):

instance number inferred from id

@property
def name(self):

human readible short description with spaces

@property
def index(self):

problem index in the benchmark Suite of origin

@property
def suite(self):

benchmark suite this problem is from

@property
def info(self):

human readible info, alias for str(self).

The format of this info string is not guarantied and may change in future.

cocoex.Problem(_interface.Problem) class documentation

`cocoex.Problem(_interface.Problem)` class documentation