stk.Tournament

class stk.Tournament(num_batches=None, batch_size=1, duplicate_molecules=True, duplicate_batches=True, key_maker=Inchi(), fitness_modifier=<function Tournament.<lambda>>, random_seed=None)[source]

Bases: Selector[T]

Yields batches of molecules through tournament selection.

In tournament selection, a random number of batches is chosen from the population to undergo a competition. In each competition, the batch with the highest fitness value is yielded. This is repeated until num_batches are yielded.

Examples

Yielding Single Molecule Batches

Yielding molecules one at a time. For example, if molecules need to be selected for mutation or the next generation.

import stk

# Make the selector.
tournament = stk.Tournament(
    num_batches=5,
    batch_size=1
)

population = {
    stk.MoleculeRecord(
        topology_graph=stk.polymer.Linear(
            building_blocks=[
                stk.BuildingBlock('BrCCBr', stk.BromoFactory()),
            ],
            repeating_unit='A',
            num_repeating_units=2,
        ),
    ): i
    for i in range(100)
}

# Select the molecules.
for selected, in tournament.select(population):
    # Do stuff with each selected molecule.
    pass

Parameters:

num_batches (int | None) – The number of batches to yield. If None then yielding will continue forever or until the generator is exhausted, whichever comes first.
batch_size (int) – The number of molecules yielded at once.
duplicate_molecules (bool) – If True the same molecule can be yielded in more than one batch.
duplicate_batches (bool) – If True the same batch can be yielded more than once.
key_maker (MoleculeKeyMaker) – Used to get the keys of molecules. If two molecules have the same key, they are considered duplicates.
fitness_modifier (Callable[[dict[T, float]], dict[T, float]]) – Takes the population on which select() is called and returns a dict, which maps records in the population to the fitness values the Selector should use.
random_seed (int | Generator | None) – The random seed to use.

Methods

select

Yield batches of molecule records from population.

select(population, included_batches=None, excluded_batches=None)

Yield batches of molecule records from population.

Parameters:

population (dict[T, float]) – A collection of molecules from which batches are selected.
included_batches (set[BatchKey] | None) – The identity keys of batches which are allowed to be yielded, if None all batches can be yielded. If not None only batches included_batches will be yielded.
excluded_batches (set[BatchKey] | None) – The identity keys of batches which are not allowed to be yielded. If None, no batch is forbidden from being yielded.

Yields:

A batch of selected molecule records.

Return type:

Iterator[Batch[T]]