Source code for scm.glompo.stoppers.bestfunctionvalueunmoving

from .basestopper import BaseStopper
from ..core.optimizerlogger import BaseLogger
from ...plams.core.settings import Settings

__all__ = ("BestFunctionValueUnmoving",)


[docs]class BestFunctionValueUnmoving(BaseStopper):
    """Considers the lowest function value seen by the optimizer thus far.
    Returns ``True`` if the tested optimizer's best value has not changed significantly in a given amount of time.

    :Parameters:

    calls
        Number of function evaluations between comparison points.
    tol
        Tolerance fraction between 0 and 1.

    :Returns:

    bool
        ``True`` if::

           abs(latest_f_value - f_value_calls_ago) <= abs(f_value_calls_ago * self.tol)
    """

    def __init__(self, calls: int, tol: float = 0):
        super().__init__()
        self.calls = calls
        self.tol = tol

    def __call__(self, log: BaseLogger, best_opt_id: int, tested_opt_id: int) -> bool:
        vals = log.get_history(tested_opt_id, "fx")
        fcalls = log.len(tested_opt_id)

        if fcalls <= self.calls:
            # If there are insufficient iterations the stopper will return False
            self.last_result = False
            return self.last_result

        best_at_calls = min(vals[: -self.calls])
        best_at_end = min(vals)
        self.last_result = abs(best_at_end - best_at_calls) <= abs(best_at_calls * self.tol)
        return self.last_result

    def __amssettings__(self, s: Settings) -> Settings:
        s.input.ams.Stopper.Type = "BestFunctionValueUnmoving"
        s.input.ams.Stopper.BestFunctionValueUnmoving.NumberOfFunctionCalls = self.calls
        s.input.ams.Stopper.BestFunctionValueUnmoving.Tolerance = self.tol
        return s