#!/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.
# pyre-strict
from ax.core.observation import (
Observation,
ObservationData,
ObservationFeatures,
separate_observations,
)
from ax.core.optimization_config import OptimizationConfig
from ax.core.parameter import ChoiceParameter, FixedParameter
from ax.core.search_space import SearchSpace
from ax.core.types import TParamValueList
from ax.exceptions.core import UserInputError
from ax.modelbridge.base import GenResults, ModelBridge
from ax.modelbridge.modelbridge_utils import (
array_to_observation_data,
get_fixed_features,
)
from ax.modelbridge.torch import (
extract_objective_weights,
extract_outcome_constraints,
validate_optimization_config,
)
from ax.models.discrete_base import DiscreteModel
from ax.models.types import TConfig
FIT_MODEL_ERROR = "Model must be fit before {action}."
[docs]
class DiscreteModelBridge(ModelBridge):
"""A model bridge for using models based on discrete parameters.
Requires that all parameters have been transformed to ChoiceParameters.
"""
# pyre-fixme[13]: Attribute `model` is never initialized.
model: DiscreteModel
# pyre-fixme[13]: Attribute `outcomes` is never initialized.
outcomes: list[str]
# pyre-fixme[13]: Attribute `parameters` is never initialized.
parameters: list[str]
# pyre-fixme[13]: Attribute `search_space` is never initialized.
search_space: SearchSpace | None
def _fit(
self,
model: DiscreteModel,
search_space: SearchSpace,
observations: list[Observation],
) -> None:
self.model = model
# Convert observations to arrays
self.parameters = list(search_space.parameters.keys())
all_metric_names: set[str] = set()
observation_features, observation_data = separate_observations(observations)
for od in observation_data:
all_metric_names.update(od.metric_names)
self.outcomes = list(all_metric_names)
# Convert observations to arrays
Xs_array, Ys_array, Yvars_array = self._convert_observations(
observation_data=observation_data,
observation_features=observation_features,
outcomes=self.outcomes,
parameters=self.parameters,
)
# Extract parameter values
parameter_values = _get_parameter_values(search_space, self.parameters)
self.model.fit(
Xs=Xs_array,
Ys=Ys_array,
Yvars=Yvars_array,
parameter_values=parameter_values,
outcome_names=self.outcomes,
)
def _predict(
self, observation_features: list[ObservationFeatures]
) -> list[ObservationData]:
# Convert observations to array
X = [
[of.parameters[param] for param in self.parameters]
for of in observation_features
]
f, cov = self.model.predict(X=X)
# Convert arrays to observations
return array_to_observation_data(f=f, cov=cov, outcomes=self.outcomes)
def _validate_gen_inputs(
self,
n: int,
search_space: SearchSpace | None = None,
optimization_config: OptimizationConfig | None = None,
pending_observations: dict[str, list[ObservationFeatures]] | None = None,
fixed_features: ObservationFeatures | None = None,
model_gen_options: TConfig | None = None,
) -> None:
"""Validate inputs to `ModelBridge.gen`.
Currently, this is only used to ensure that `n` is a positive integer or -1.
"""
if n < 1 and n != -1:
raise UserInputError(
f"Attempted to generate n={n} points. Number of points to generate "
"must be either a positive integer or -1."
)
def _gen(
self,
n: int,
search_space: SearchSpace,
pending_observations: dict[str, list[ObservationFeatures]],
fixed_features: ObservationFeatures | None,
model_gen_options: TConfig | None = None,
optimization_config: OptimizationConfig | None = None,
) -> GenResults:
"""Generate new candidates according to search_space and
optimization_config.
The outcome constraints should be transformed to no longer be relative.
"""
# Validation
if not self.parameters:
raise ValueError(FIT_MODEL_ERROR.format(action="_gen"))
# Extract parameter values
parameter_values = _get_parameter_values(search_space, self.parameters)
# Extract objective and outcome constraints
if len(self.outcomes) == 0 or optimization_config is None:
objective_weights = None
outcome_constraints = None
else:
validate_optimization_config(optimization_config, self.outcomes)
objective_weights = extract_objective_weights(
objective=optimization_config.objective, outcomes=self.outcomes
)
outcome_constraints = extract_outcome_constraints(
outcome_constraints=optimization_config.outcome_constraints,
outcomes=self.outcomes,
)
# Get fixed features
fixed_features_dict = get_fixed_features(
fixed_features=fixed_features, param_names=self.parameters
)
# Pending observations
if len(pending_observations) == 0:
pending_array: list[list[TParamValueList]] | None = None
else:
pending_array = [[] for _ in self.outcomes]
for metric_name, po_list in pending_observations.items():
pending_array[self.outcomes.index(metric_name)] = [
[po.parameters[p] for p in self.parameters] for po in po_list
]
# Generate the candidates
X, w, gen_metadata = self.model.gen(
n=n,
parameter_values=parameter_values,
objective_weights=objective_weights,
outcome_constraints=outcome_constraints,
fixed_features=fixed_features_dict, # pyre-ignore
pending_observations=pending_array,
model_gen_options=model_gen_options,
)
observation_features = []
for x in X:
observation_features.append(
ObservationFeatures(
parameters={p: x[i] for i, p in enumerate(self.parameters)}
)
)
# TODO[drfreund, bletham]: implement best_point identification and
# return best_point instead of None
return GenResults(
observation_features=observation_features,
weights=w,
gen_metadata=gen_metadata,
)
def _cross_validate(
self,
search_space: SearchSpace,
cv_training_data: list[Observation],
cv_test_points: list[ObservationFeatures],
use_posterior_predictive: bool = False,
) -> list[ObservationData]:
"""Make predictions at cv_test_points using only the data in obs_feats
and obs_data.
"""
observation_features, observation_data = separate_observations(cv_training_data)
Xs_train, Ys_train, Yvars_train = self._convert_observations(
observation_data=observation_data,
observation_features=observation_features,
outcomes=self.outcomes,
parameters=self.parameters,
)
X_test = [
[obsf.parameters[param] for param in self.parameters]
for obsf in cv_test_points
]
# Use the model to do the cross validation
f_test, cov_test = self.model.cross_validate(
Xs_train=Xs_train,
Ys_train=Ys_train,
Yvars_train=Yvars_train,
X_test=X_test,
use_posterior_predictive=use_posterior_predictive,
)
# Convert array back to ObservationData
return array_to_observation_data(f=f_test, cov=cov_test, outcomes=self.outcomes)
@classmethod
def _convert_observations(
cls,
observation_data: list[ObservationData],
observation_features: list[ObservationFeatures],
outcomes: list[str],
parameters: list[str],
) -> tuple[list[list[TParamValueList]], list[list[float]], list[list[float]]]:
Xs: list[list[TParamValueList]] = [[] for _ in outcomes]
Ys: list[list[float]] = [[] for _ in outcomes]
Yvars: list[list[float]] = [[] for _ in outcomes]
for i, obsf in enumerate(observation_features):
try:
x = [obsf.parameters[param] for param in parameters]
except (KeyError, TypeError):
# Out of design point
raise ValueError("Out of design points cannot be converted.")
for j, m in enumerate(observation_data[i].metric_names):
k = outcomes.index(m)
Xs[k].append(x)
Ys[k].append(observation_data[i].means[j])
Yvars[k].append(observation_data[i].covariance[j, j])
return Xs, Ys, Yvars
def _get_parameter_values(
search_space: SearchSpace, param_names: list[str]
) -> list[TParamValueList]:
"""Extract parameter values from a search space of discrete parameters."""
parameter_values: list[TParamValueList] = []
for p_name in param_names:
p = search_space.parameters[p_name]
# Validation
if isinstance(p, ChoiceParameter):
# Set values
parameter_values.append(p.values)
elif isinstance(p, FixedParameter):
parameter_values.append([p.value])
else:
raise ValueError(f"{p} not ChoiceParameter or FixedParameter")
return parameter_values
