import logging
from ignite.engine import Engine
class EarlyStopping(object):
"""EarlyStopping handler can be used to stop the training if no improvement after a given number of events
Args:
patience (int):
Number of events to wait if no improvement and then stop the training
score_function (Callable):
It should be a function taking a single argument, an `ignite.engine.Engine` object,
and return a score `float`. An improvement is considered if the score is higher.
Examples:
.. code-block:: python
from ignite.engine import Engine, Events
from ignite.handlers import EarlyStopping
def score_function(engine):
val_loss = engine.state.metrics['nll']
return -val_loss
handler = EarlyStopping(patience=10, score_function=score_function, trainer=trainer)
evaluator.add_event_handler(Events.COMPLETED, handler)
"""
def __init__(self, patience, score_function, trainer):
assert callable(score_function), "Argument score_function should be a function"
assert patience > 0, "Argument patience should be positive"
assert isinstance(trainer, Engine), "Argument trainer should be an instance of Engine"
self.score_function = score_function
self.patience = patience
self.trainer = trainer
self.counter = 0
self.best_score = None
self._logger = logging.getLogger(__name__ + "." + self.__class__.__name__)
self._logger.addHandler(logging.NullHandler())
def __call__(self, engine):
score = self.score_function(engine)
if self.best_score is None:
self.best_score = score
elif score < self.best_score:
self.counter += 1
self._logger.debug("EarlyStopping: %i / %i" % (self.counter, self.patience))
if self.counter >= self.patience:
self._logger.info("EarlyStopping: Stop training")
self.trainer.terminate()
else:
self.best_score = score
self.counter = 0
