Observer entities

It is possible to attach any number of observers to any algorithm to get information from each iteration. For example, a basic algorithm observer will print the number of evaluations, the objectives from the best individual in the population and the computing time:

basic = BasicAlgorithmObserver(frequency=1.0)
algorithm.observable.register(observer=basic)

A progress bar observer will print a smart progress meter that increases, on each iteration, a fixed value (step) until the maximum is reached.

max_evaluations = 25000

algorithm = GeneticAlgorithm(
     problem=problem,
     population_size=100,
     offspring_population_size=100,
     mutation=BitFlipMutation(1.0 / problem.number_of_bits),
     crossover=SPXCrossover(0.9),
     selection=BinaryTournamentSelection(),
     termination_criterion=StoppingByEvaluations(max=25000)
 )

progress_bar = ProgressBarObserver(max=max_evaluations)
algorithm.observable.register(progress_bar)

algorithm.run()

$ Progress:  50%|#####     | 12500/25000 [13:59<14:12, 14.66it/s]

A full list of all available observers can be found at the jmetal.util.observer module.