import tempfile
from contextlib import contextmanager
from pathlib import Path
from typing import Callable, Dict, List, Optional, Union
from lightgbm.basic import Booster
from lightgbm.callback import CallbackEnv
from ray import train
from ray.train import Checkpoint
from ray.tune.utils import flatten_dict
from ray.util.annotations import PublicAPI
[docs]@PublicAPI(stability="beta")
class RayTrainReportCallback:
"""Creates a callback that reports metrics and checkpoints model.
Args:
metrics: Metrics to report. If this is a list,
each item should be a metric key reported by LightGBM,
and it will be reported to Ray Train/Tune under the same name.
This can also be a dict of {<key-to-report>: <lightgbm-metric-key>},
which can be used to rename LightGBM default metrics.
filename: Customize the saved checkpoint file type by passing
a filename. Defaults to "model.txt".
frequency: How often to save checkpoints, in terms of iterations.
Defaults to 0 (no checkpoints are saved during training).
checkpoint_at_end: Whether or not to save a checkpoint at the end of training.
results_postprocessing_fn: An optional Callable that takes in
the metrics dict that will be reported (after it has been flattened)
and returns a modified dict.
Examples
--------
Reporting checkpoints and metrics to Ray Tune when running many
independent xgboost trials (without data parallelism within a trial).
.. testcode::
:skipif: True
import lightgbm
from ray.train.lightgbm import RayTrainReportCallback
config = {
# ...
"metric": ["binary_logloss", "binary_error"],
}
# Report only log loss to Tune after each validation epoch.
bst = lightgbm.train(
...,
callbacks=[
RayTrainReportCallback(
metrics={"loss": "eval-binary_logloss"}, frequency=1
)
],
)
Loading a model from a checkpoint reported by this callback.
.. testcode::
:skipif: True
from ray.train.lightgbm import RayTrainReportCallback
# Get a `Checkpoint` object that is saved by the callback during training.
result = trainer.fit()
booster = RayTrainReportCallback.get_model(result.checkpoint)
"""
CHECKPOINT_NAME = "model.txt"
def __init__(
self,
metrics: Optional[Union[str, List[str], Dict[str, str]]] = None,
filename: str = CHECKPOINT_NAME,
frequency: int = 0,
checkpoint_at_end: bool = True,
results_postprocessing_fn: Optional[
Callable[[Dict[str, Union[float, List[float]]]], Dict[str, float]]
] = None,
):
if isinstance(metrics, str):
metrics = [metrics]
self._metrics = metrics
self._filename = filename
self._frequency = frequency
self._checkpoint_at_end = checkpoint_at_end
self._results_postprocessing_fn = results_postprocessing_fn
[docs] @classmethod
def get_model(
cls, checkpoint: Checkpoint, filename: str = CHECKPOINT_NAME
) -> Booster:
"""Retrieve the model stored in a checkpoint reported by this callback.
Args:
checkpoint: The checkpoint object returned by a training run.
The checkpoint should be saved by an instance of this callback.
filename: The filename to load the model from, which should match
the filename used when creating the callback.
"""
with checkpoint.as_directory() as checkpoint_path:
return Booster(model_file=Path(checkpoint_path, filename).as_posix())
def _get_report_dict(self, evals_log: Dict[str, Dict[str, list]]) -> dict:
result_dict = flatten_dict(evals_log, delimiter="-")
if not self._metrics:
report_dict = result_dict
else:
report_dict = {}
for key in self._metrics:
if isinstance(self._metrics, dict):
metric = self._metrics[key]
else:
metric = key
report_dict[key] = result_dict[metric]
if self._results_postprocessing_fn:
report_dict = self._results_postprocessing_fn(report_dict)
return report_dict
def _get_eval_result(self, env: CallbackEnv) -> dict:
eval_result = {}
for entry in env.evaluation_result_list:
data_name, eval_name, result = entry[0:3]
if len(entry) > 4:
stdv = entry[4]
suffix = "-mean"
else:
stdv = None
suffix = ""
if data_name not in eval_result:
eval_result[data_name] = {}
eval_result[data_name][eval_name + suffix] = result
if stdv is not None:
eval_result[data_name][eval_name + "-stdv"] = stdv
return eval_result
@contextmanager
def _get_checkpoint(self, model: Booster) -> Optional[Checkpoint]:
with tempfile.TemporaryDirectory() as temp_checkpoint_dir:
model.save_model(Path(temp_checkpoint_dir, self._filename).as_posix())
yield Checkpoint.from_directory(temp_checkpoint_dir)
def __call__(self, env: CallbackEnv) -> None:
eval_result = self._get_eval_result(env)
report_dict = self._get_report_dict(eval_result)
on_last_iter = env.iteration == env.end_iteration - 1
checkpointing_disabled = self._frequency == 0
# Ex: if frequency=2, checkpoint_at_end=True and num_boost_rounds=10,
# you will checkpoint at iterations 1, 3, 5, ..., and 9 (checkpoint_at_end)
# (counting from 0)
should_checkpoint = (
not checkpointing_disabled and (env.iteration + 1) % self._frequency == 0
) or (on_last_iter and self._checkpoint_at_end)
if should_checkpoint:
with self._get_checkpoint(model=env.model) as checkpoint:
train.report(report_dict, checkpoint=checkpoint)
else:
train.report(report_dict)