optuna.trial.FrozenTrial

class optuna.trial.FrozenTrial(number, state, value, datetime_start, datetime_complete, params, distributions, user_attrs, system_attrs, intermediate_values, trial_id, *, values=None)[source]

Status and results of a Trial.

An object of this class has the same methods as Trial, but is not associated with, nor has any references to a Study.

It is therefore not possible to make persistent changes to a storage from this object by itself, for instance by using set_user_attr().

It will suggest the parameter values stored in params and will not sample values from any distributions.

It can be passed to objective functions (see optimize()) and is useful for deploying optimization results.

Example

Re-evaluate an objective function with parameter values optimized study.

import optuna

def objective(trial):
    x = trial.suggest_float("x", -1, 1)
    return x**2

study = optuna.create_study()
study.optimize(objective, n_trials=3)

assert objective(study.best_trial) == study.best_value

Note

Instances are mutable, despite the name. For instance, set_user_attr() will update user attributes of objects in-place.

Example:

Overwritten attributes.

import copy
import datetime

import optuna


def objective(trial):
    x = trial.suggest_float("x", -1, 1)

    # this user attribute always differs
    trial.set_user_attr("evaluation time", datetime.datetime.now())

    return x**2


study = optuna.create_study()
study.optimize(objective, n_trials=3)

best_trial = study.best_trial
best_trial_copy = copy.deepcopy(best_trial)

# re-evaluate
objective(best_trial)

# the user attribute is overwritten by re-evaluation
assert best_trial.user_attrs != best_trial_copy.user_attrs

Note

Please refer to Trial for details of methods and properties.

Parameters:

number (int)
state (TrialState)
value (float | None)
datetime_start (datetime.datetime | None)
datetime_complete (datetime.datetime | None)
params (dict[str, Any])
distributions (dict[str, BaseDistribution])
user_attrs (dict[str, Any])
system_attrs (dict[str, Any])
intermediate_values (dict[int, float])
trial_id (int)
values (Sequence[float] | None)

number: Unique and consecutive number of Trial for each Study. Note that this field uses zero-based numbering.

state: TrialState of the Trial.

value: Objective value of the Trial. value and values must not be specified at the same time.

values: Sequence of objective values of the Trial. The length is greater than 1 if the problem is multi-objective optimization. value and values must not be specified at the same time.

datetime_start: Datetime where the Trial started.

datetime_complete: Datetime where the Trial finished.

params: Dictionary that contains suggested parameters.

distributions: Dictionary that contains the distributions of params.

user_attrs: Dictionary that contains the attributes of the Trial set with optuna.trial.Trial.set_user_attr().

system_attrs: Dictionary that contains the attributes of the Trial set with optuna.trial.Trial.set_system_attr().

intermediate_values: Intermediate objective values set with optuna.trial.Trial.report().

Methods

`report`(value, step)	Interface of report function.
`set_system_attr`(key, value)
`set_user_attr`(key, value)
`should_prune`()	Suggest whether the trial should be pruned or not.
`suggest_categorical`(...)
`suggest_discrete_uniform`(name, low, high, q)
`suggest_float`(name, low, high, *[, step, log])
`suggest_int`(name, low, high, *[, step, log])
`suggest_loguniform`(name, low, high)
`suggest_uniform`(name, low, high)

Attributes

`datetime_start`
`distributions`
`duration`	Return the elapsed time taken to complete the trial.
`last_step`	Return the maximum step of `intermediate_values` in the trial.
`number`
`params`
`system_attrs`
`user_attrs`
`value`
`values`

property duration: timedelta | None

Return the elapsed time taken to complete the trial.

Returns:: The duration.

property last_step: int | None

Return the maximum step of intermediate_values in the trial.

Returns:: The maximum step of intermediates.

report(value, step)[source]

Interface of report function.

Since FrozenTrial is not pruned, this report function does nothing.