Source code for optuna.integration.keras

import optuna
from optuna import type_checking

if type_checking.TYPE_CHECKING:
    from typing import Dict  # NOQA

try:
    from keras.callbacks import Callback

    _available = True
except ImportError as e:
    _import_error = e
    # KerasPruningExtension is disabled because Keras is not available.
    _available = False
    # This alias is required to avoid ImportError at KerasPruningExtension definition.
    Callback = object


[docs]class KerasPruningCallback(Callback): """Keras callback to prune unpromising trials. See `the example <https://github.com/optuna/optuna/blob/master/ examples/pruning/keras_integration.py>`__ if you want to add a pruning callback which observes validation accuracy. Args: trial: A :class:`~optuna.trial.Trial` corresponding to the current evaluation of the objective function. monitor: An evaluation metric for pruning, e.g., ``val_loss`` and ``val_accuracy``. Please refer to `keras.Callback reference <https://keras.io/callbacks/#callback>`_ for further details. interval: Check if trial should be pruned every n-th epoch. By default ``interval=1`` and pruning is performed after every epoch. Increase ``interval`` to run several epochs faster before applying pruning. """ def __init__(self, trial, monitor, interval=1): # type: (optuna.trial.Trial, str, int) -> None super(KerasPruningCallback, self).__init__() _check_keras_availability() self._trial = trial self._monitor = monitor self._interval = interval def on_epoch_end(self, epoch, logs=None): # type: (int, Dict[str, float]) -> None if (epoch + 1) % self._interval != 0: return logs = logs or {} current_score = logs.get(self._monitor) if current_score is None: return self._trial.report(float(current_score), step=epoch) if self._trial.should_prune(): message = "Trial was pruned at epoch {}.".format(epoch) raise optuna.TrialPruned(message)
def _check_keras_availability(): # type: () -> None if not _available: raise ImportError( "Keras is not available. Please install Keras to use this feature. " "Keras can be installed by executing `$ pip install keras tensorflow`. " "For further information, please refer to the installation guide of Keras. " "(The actual import error is as follows: " + str(_import_error) + ")" )