ribs.emitters.rankers.TwoStageImprovementRanker

class ribs.emitters.rankers.TwoStageImprovementRanker(seed: int | integer | None = None)[source]

Ranks solutions based on status and on improvement in the objective.

This ranker originates in Fontaine 2020 in which it was referred to as “Improvement Emitter”. This ranker ranks solutions in two stages. First, solutions are ranked by “status” – those that found a new cell in the archive rank above those that improved an existing cell, which rank above those that were not added to the archive. Second, solutions are ranked by the “value” returned by archive add methods, such as ribs.archives.GridArchive.add().

Methods

rank(emitter, archive, data, add_info)

Generates a list of indices that represents an ordering of solutions.

reset(emitter, archive)

Resets the internal state of the ranker.
rank(emitter: EmitterBase, archive: ArchiveBase, data: dict[str, ndarray], add_info: dict[str, ndarray]) → tuple[ndarray, ndarray][source]

Generates a list of indices that represents an ordering of solutions.

Parameters:
emitter: EmitterBase

Emitter that this ranker object belongs to.

archive: ArchiveBase

Archive used by emitter when creating and inserting solutions.

data: dict[str, ndarray]

Dict mapping from field names like solution and objective to arrays with data for the solutions.

add_info: dict[str, ndarray]

Information returned by an archive’s add() method.

Returns:

The first array (shape (batch_size,)) is an array of indices representing a ranking of the solutions and the second array (shape (batch_size,) or (batch_size, n_values)) is an array of values that this ranker used to rank the solutions. batch_size is the number of solutions and n_values is the number of values that the rank function used.

reset(emitter: EmitterBase, archive: ArchiveBase) → None

Resets the internal state of the ranker.

Parameters:
emitter: EmitterBase

Emitter that this ranker object belongs to.

archive: ArchiveBase

Archive used by emitter when creating and inserting solutions.