Source code for monai.handlers.validation_handler

# Copyright 2020 - 2021 MONAI Consortium
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#     http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
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from typing import TYPE_CHECKING

from monai.engines.evaluator import Evaluator
from monai.utils import exact_version, optional_import

Events, _ = optional_import("ignite.engine", "0.4.2", exact_version, "Events")
if TYPE_CHECKING:
    from ignite.engine import Engine
else:
    Engine, _ = optional_import("ignite.engine", "0.4.2", exact_version, "Engine")


[docs]class ValidationHandler: """ Attach validator to the trainer engine in Ignite. It can support to execute validation every N epochs or every N iterations. """ def __init__(self, validator: Evaluator, interval: int, epoch_level: bool = True) -> None: """ Args: validator: run the validator when trigger validation, suppose to be Evaluator. interval: do validation every N epochs or every N iterations during training. epoch_level: execute validation every N epochs or N iterations. `True` is epoch level, `False` is iteration level. Raises: TypeError: When ``validator`` is not a ``monai.engines.evaluator.Evaluator``. """ if not isinstance(validator, Evaluator): raise TypeError(f"validator must be a monai.engines.evaluator.Evaluator but is {type(validator).__name__}.") self.validator = validator self.interval = interval self.epoch_level = epoch_level
[docs] def attach(self, engine: Engine) -> None: """ Args: engine: Ignite Engine, it can be a trainer, validator or evaluator. """ if self.epoch_level: engine.add_event_handler(Events.EPOCH_COMPLETED(every=self.interval), self) else: engine.add_event_handler(Events.ITERATION_COMPLETED(every=self.interval), self)
def __call__(self, engine: Engine) -> None: """ Args: engine: Ignite Engine, it can be a trainer, validator or evaluator. """ self.validator.run(engine.state.epoch)