Source code for ax.core.metric

#!/usr/bin/env python3
# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

from __future__ import annotations

from typing import Any, Dict, Iterable, Optional, Tuple, Type, TYPE_CHECKING

from ax.core.data import Data
from ax.utils.common.base import SortableBase
from ax.utils.common.serialization import extract_init_args, serialize_init_args
from ax.utils.common.typeutils import checked_cast

if TYPE_CHECKING:  # pragma: no cover
    # import as module to make sphinx-autodoc-typehints happy
    from ax import core  # noqa F401


[docs]class Metric(SortableBase): """Base class for representing metrics. The `fetch_trial_data` method is the essential method to override when subclassing, which specifies how to retrieve a Metric, for a given trial. A Metric must return a Data object, which requires (at minimum) the following: https://ax.dev/api/_modules/ax/core/data.html#Data.required_columns Attributes: lower_is_better: Flag for metrics which should be minimized. properties: Properties specific to a particular metric. """ data_constructor: Type[Data] = Data def __init__( self, name: str, lower_is_better: Optional[bool] = None, properties: Optional[Dict[str, Any]] = None, ) -> None: """Inits Metric. Args: name: Name of metric. lower_is_better: Flag for metrics which should be minimized. properties: Dictionary of this metric's properties """ self._name = name self.lower_is_better = lower_is_better self.properties = properties or {}
[docs] @classmethod def is_available_while_running(cls) -> bool: """Whether metrics of this class are available while the trial is running. Metrics that are not available while the trial is running are assumed to be available only upon trial completion. For such metrics, data is assumed to never change once the trial is completed. NOTE: If this method returns `False`, data-fetching via `experiment.fetch_data` will return the data cached on the experiment (for the metrics of the given class) whenever its available. Data is cached on experiment when attached via `experiment.attach_data`. """ return False
@property def name(self) -> str: """Get name of metric.""" return self._name @property def fetch_multi_group_by_metric(self) -> Type[Metric]: """Metric class, with which to group this metric in `Experiment._metrics_by_class`, which is used to combine metrics on experiment into groups and then fetch their data via `Metric.fetch_trial_data_multi` for each group. NOTE: By default, this property will just return the class on which it is defined; however, in some cases it is useful to group metrics by their superclass, in which case this property should return that superclass. """ return self.__class__
[docs] @classmethod def serialize_init_args(cls, metric: Metric) -> Dict[str, Any]: """Serialize the properties needed to initialize the metric. Used for storage. """ return serialize_init_args(object=metric)
[docs] @classmethod def deserialize_init_args(cls, args: Dict[str, Any]) -> Dict[str, Any]: """Given a dictionary, extract the properties needed to initialize the metric. Used for storage. """ return extract_init_args(args=args, class_=cls)
[docs] def fetch_trial_data(self, trial: core.base_trial.BaseTrial, **kwargs: Any) -> Data: """Fetch data for one trial.""" raise NotImplementedError( f"Metric {self.name} does not implement data-fetching logic." ) # pragma: no cover
[docs] def fetch_experiment_data( self, experiment: core.experiment.Experiment, **kwargs: Any ) -> Data: """Fetch this metric's data for an experiment. Default behavior is to fetch data from all trials expecting data and concatenate the results. """ return self.data_constructor.from_multiple_data( [ checked_cast( self.data_constructor, self.fetch_trial_data(trial, **kwargs) ) if trial.status.expecting_data else self.data_constructor() for trial in experiment.trials.values() ], )
[docs] @classmethod def fetch_trial_data_multi( cls, trial: core.base_trial.BaseTrial, metrics: Iterable[Metric], **kwargs: Any ) -> Data: """Fetch multiple metrics data for one trial. Default behavior calls `fetch_trial_data` for each metric. Subclasses should override this to trial data computation for multiple metrics. """ dat = cls.data_constructor.from_multiple_data( [metric.fetch_trial_data(trial, **kwargs) for metric in metrics] ) return dat
[docs] @classmethod def fetch_experiment_data_multi( cls, experiment: core.experiment.Experiment, metrics: Iterable[Metric], trials: Optional[Iterable[core.base_trial.BaseTrial]] = None, **kwargs: Any, ) -> Data: """Fetch multiple metrics data for an experiment. Default behavior calls `fetch_trial_data_multi` for each trial. Subclasses should override to batch data computation across trials + metrics. """ return cls.data_constructor.from_multiple_data( [ cls.fetch_trial_data_multi(trial, metrics, **kwargs) if trial.status.expecting_data else cls.data_constructor() for trial in (experiment.trials.values() if trials is None else trials) ] )
[docs] @classmethod def lookup_or_fetch_experiment_data_multi( cls, experiment: core.experiment.Experiment, metrics: Iterable[Metric], trials: Optional[Iterable[core.base_trial.BaseTrial]] = None, **kwargs: Any, ) -> Tuple[Data, bool]: """Fetch or lookup (with fallback to fetching) data for given metrics, depending on whether they are available while running. Return a tuple containing the data, along with a boolean that will be True if new data was fetched, and False if all data was looked up from cache. If metric is available while running, its data can change (and therefore we should always re-fetch it). If metric is available only upon trial completion, its data does not change, so we can look up that data on the experiment and only fetch the data that is not already attached to the experiment. NOTE: If fetching data for a metrics class that is only available upon trial completion, data fetched in this function (data that was not yet available on experiment) will be attached to experiment. """ # If this metric is available while trial is running, just default to # `fetch_experiment_data_multi`. if cls.is_available_while_running(): fetched_data = cls.fetch_experiment_data_multi( experiment=experiment, metrics=metrics, trials=trials, **kwargs ) return fetched_data, True # If this metric is available only upon trial completion, look up data # on experiment and only fetch data that is not already cached. if trials is None: completed_trials = experiment.trials_by_status[ core.base_trial.TrialStatus.COMPLETED ] else: completed_trials = [t for t in trials if t.status.is_completed] if not completed_trials: return cls.data_constructor(), False trials_data = [] contains_new_data = False for trial in completed_trials: cached_trial_data = experiment.lookup_data_for_trial( trial_index=trial.index, )[0] cached_metric_names = cached_trial_data.metric_names metrics_to_fetch = [m for m in metrics if m.name not in cached_metric_names] if not metrics_to_fetch: # If all needed data fetched from cache, no need to fetch any other data # for trial. trials_data.append(cached_trial_data) continue try: fetched_trial_data = cls.fetch_experiment_data_multi( experiment=experiment, metrics=metrics_to_fetch, trials=[trial], **kwargs, ) contains_new_data = True except NotImplementedError: # Metric does not implement fetching logic and only uses lookup. fetched_trial_data = cls.data_constructor() final_data = cls.data_constructor.from_multiple_data( [cached_trial_data, fetched_trial_data] ) trials_data.append(final_data) return ( cls.data_constructor.from_multiple_data( trials_data, subset_metrics=[m.name for m in metrics] ), contains_new_data, )
[docs] def clone(self) -> "Metric": """Create a copy of this Metric.""" cls = type(self) return cls( **serialize_init_args(self), )
def __repr__(self) -> str: return "{class_name}('{metric_name}')".format( class_name=self.__class__.__name__, metric_name=self.name ) @property def _unique_id(self) -> str: return str(self)