Class ProgramDatabase

openevolve/database.py:113–2563

Database for storing and sampling programs during evolution The database implements a combination of MAP-Elites algorithm and island-based population model to maintain diversity during evolution. It also tracks the absolute best program separately to ensure it's never lost.

class ProgramDatabase:
    """
    Database for storing and sampling programs during evolution

    The database implements a combination of MAP-Elites algorithm and
    island-based population model to maintain diversity during evolution.
    It also tracks the absolute best program separately to ensure it's never lost.
    """

    def __init__(self, config: DatabaseConfig):
        self.config = config

        # In-memory program storage
        self.programs: Dict[str, Program] = {}

        # Per-island feature grids for MAP-Elites
        self.island_feature_maps: List[Dict[str, str]] = [{} for _ in range(config.num_islands)]

        # Handle both int and dict types for feature_bins
        if isinstance(config.feature_bins, int):
            self.feature_bins = max(
                config.feature_bins,
                int(pow(config.archive_size, 1 / len(config.feature_dimensions)) + 0.99),
            )
        else:
            # If dict, keep as is (we'll use feature_bins_per_dim instead)
            self.feature_bins = 10  # Default fallback for backward compatibility

        # Island populations
        self.islands: List[Set[str]] = [set() for _ in range(config.num_islands)]

        # Island management attributes
        self.current_island: int = 0
        self.island_generations: List[int] = [0] * config.num_islands
        self.last_migration_generation: int = 0
        self.migration_interval: int = getattr(config, "migration_interval", 10)  # Default to 10
        self.migration_rate: float = getattr(config, "migration_rate", 0.1)  # Default to 0.1

        # Archive of elite programs
        self.archive: Set[str] = set()

        # Track the absolute best program separately
        self.best_program_id: Optional[str] = None

        # Track best program per island for proper island-based evolution
        self.island_best_programs: List[Optional[str]] = [None] * config.num_islands

        # Track the last iteration number (for resuming)
        self.last_iteration: int = 0

        # Load database from disk if path is provided
        if config.db_path and os.path.exists(config.db_path):
            self.load(config.db_path)

        # Prompt log
        self.prompts_by_program: Dict[str, Dict[str, Dict[str, str]]] = None

        # Set random seed for reproducible sampling if specified