Remove `restart_strategy` and `inc_popsize` to simplify `CmaEsSampler` by sawa3030 · Pull Request #6025 · optuna/optuna

sawa3030 · 2025-03-28T09:22:42Z

Motivation

Simplify the implementation of CmaEsSampler by removing support for restart strategies. The current implementation with restart_strategy will be put into OptunaHub

Summary of Changes

Removed support for restart_strategy and inc_popsize options in CmaEsSampler
Cleaned up related logic:
- Removed associated attributes from _CmaEsAttrKeys, including popsize, n_restarts, n_restarts_with_large, poptype, small_n_eval, and large_n_eval
- Eliminated usage of set_trial_system_attr since state tracking is no longer needed
Updated unit tests accordingly

y0z · 2025-04-07T03:42:03Z

@c-bata @HideakiImamura
Could you review this PR?

HideakiImamura

Thanks for the PR. Basically, LGTM. I have several comments. PTAL.

HideakiImamura · 2025-04-09T23:45:53Z

optuna/samplers/_cmaes.py

-                versions without prior notice. See
-                https://github.com/optuna/optuna/releases/tag/v2.1.0.
+            .. warning::
+                Deprecated in v4.3.0. ``consider_prior`` argument will be removed in the future.


Suggested change

Deprecated in v4.3.0. ``consider_prior`` argument will be removed in the future.

Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.

HideakiImamura · 2025-04-09T23:46:17Z

optuna/samplers/_cmaes.py

+                Deprecated in v4.3.0. ``consider_prior`` argument will be removed in the future.
+                The removal of this feature is currently scheduled for v6.0.0,
+                but this schedule is subject to change.
+                See https://github.com/optuna/optuna/releases/tag/v4.3.0.


Suggested change

See https://github.com/optuna/optuna/releases/tag/v4.3.0.

See https://github.com/optuna/optuna/releases/tag/v4.4.0.

In addition, inc_popsize also should be deprecated and the explanation of popsize should be changed.

HideakiImamura · 2025-04-09T23:48:58Z

optuna/samplers/_cmaes.py

    ) -> None:
+        if restart_strategy is not None:
+            msg = _deprecated._DEPRECATION_WARNING_TEMPLATE.format(
+                name="`restart_strategy`", d_ver="4.3.0", r_ver="6.0.0"


Suggested change

name="`restart_strategy`", d_ver="4.3.0", r_ver="6.0.0"

name="`restart_strategy`", d_ver="4.4.0", r_ver="6.0.0"

HideakiImamura · 2025-04-10T00:01:21Z

optuna/samplers/_cmaes.py

        self._search_space = IntersectionSearchSpace()
        self._consider_pruned_trials = consider_pruned_trials
-        self._restart_strategy = restart_strategy
        self._initial_popsize = popsize


The population size is fixed (here or in the sample_relative). How about renaming this self._popsize?

optuna/samplers/_cmaes.py

sawa3030 · 2025-04-10T00:59:39Z

Thank you for the review. I’ll make the necessary updates later.
For now, I’ve added the original implementation to OptunaHub.

HideakiImamura

Thanks for the update. I have several another comments. Please take a look.

HideakiImamura · 2025-04-18T06:55:02Z

optuna/samplers/_cmaes.py

+                Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.
+                The removal of this feature is currently scheduled for v6.0.0,
+                but this schedule is subject to change.
+                See https://github.com/optuna/optuna/releases/tag/v4.4.0.
+                `restart_strategy` will be supported in OptunaHub.


There seems to be a missing message that says you can't actually use the feature.

HideakiImamura · 2025-04-18T07:05:16Z

optuna/samplers/_cmaes.py

+            .. warning::
+                Deprecated along with ``restart_strategy``.


Deprecation messages should be written at the same level of text as restart_strategy without simplification.

HideakiImamura · 2025-04-18T07:06:07Z

optuna/samplers/_cmaes.py

        lr_adapt: bool = False,
        source_trials: list[FrozenTrial] | None = None,
    ) -> None:
+        if restart_strategy is not None:


The deprecation message should also be emitted for inc_popsize.

sawa3030 · 2025-04-21T03:01:10Z

@HideakiImamura Thank you for the review. I've made the update accordingly. PTAL!

c-bata

Thank you for your pull request! I confirmed that this PR does not break the exisiting behavior using the following code.

import optuna
import optunahub
 
bbob = optunahub.load_module("benchmarks/bbob")
sphere2d = bbob.Problem(function_id=1, dimension=2, instance_id=1)

storage = optuna.storages.get_storage("sqlite:///cmaes_benchmark.db")

sampler = optuna.samplers.CmaEsSampler(seed=1)
study = optuna.create_study(
    sampler=sampler,
    directions=sphere2d.directions,
    study_name="cmaes_pr6025",
    storage=storage
)
study.optimize(sphere2d, n_trials=500)

I've also left a few minor suggestions.

c-bata · 2025-04-21T08:58:41Z

optuna/samplers/_cmaes.py

        lr_adapt: bool = False,
        source_trials: list[FrozenTrial] | None = None,
    ) -> None:
+        if restart_strategy is not None or inc_popsize != 2:


How about changing the default value for inc_popsize to -1?

Suggested change

if restart_strategy is not None or inc_popsize != 2:

if restart_strategy is not None or inc_popsize != -1:

This would allow us to show a warning message when users explicitly specify inc_popsize=2.

c-bata · 2025-04-21T09:05:19Z

optuna/samplers/_cmaes.py

-            optimizer = self._init_optimizer(
-                trans, study.direction, population_size=self._initial_popsize
-            )
+            optimizer = self._init_optimizer(trans, study.direction, population_size=self._popsize)


I think we could simply removing population_size argument from _init_optimizer() method. What do you think?

Suggested change

optimizer = self._init_optimizer(trans, study.direction, population_size=self._popsize)

optimizer = self._init_optimizer(trans, study.direction)

c-bata · 2025-04-21T09:07:53Z

optuna/samplers/_cmaes.py

+        if self._popsize is None:
+            self._popsize = 4 + math.floor(3 * math.log(len(trans.bounds)))


These lines can be simply removed. You can access to optimizer.population_size property method instead.

Suggested change

if self._popsize is None:

self._popsize = 4 + math.floor(3 * math.log(len(trans.bounds)))

See https://github.com/CyberAgentAILab/cmaes/blob/f0749088ec53aca6f056c93faed71a775351591a/cmaes/_cma.py#L240-L243 for details.

HideakiImamura

Thanks for the update. Almost LGTM! I have two minor comments. PTAL.

HideakiImamura · 2025-04-23T02:00:53Z

optuna/samplers/_cmaes.py

            or ``restart_strategy = 'bipop'`` is specified.

+            .. warning::
+                Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.


Suggested change

Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.

Deprecated in v4.4.0. ``inc_popsize`` argument will be removed in the future.

HideakiImamura · 2025-04-23T02:01:12Z

optuna/samplers/_cmaes.py

+                From v4.4.0 onward, ``restart_strategy`` automatically falls back to ``None``, and
+                ``restart_strategy`` will be supported in OptunaHub.


Suggested change

From v4.4.0 onward, ``restart_strategy`` automatically falls back to ``None``, and

``restart_strategy`` will be supported in OptunaHub.

From v4.4.0 onward, ``inc_popsize`` automatically falls back to ``None``, and

``inc_popsize`` will be supported in OptunaHub.

This reverts commit 8dab48d.

sawa3030 · 2025-04-28T01:41:07Z

Still investigating the cause of the docs/readthedoc.org:optuna test failure in the latest commit.

sawa3030 · 2025-04-30T02:47:55Z

@c-bata @HideakiImamura Thank you for your feedback and patience. Everything should be updated now. PTAL!

HideakiImamura

Thanks for the update! LGTM!

c-bata

LGTM! Thank you for your contribution.

c-bata · 2025-05-01T09:41:26Z

optuna/samplers/_cmaes.py

-        def optimizer_key_template(restart: int) -> str:
-            if self._restart_strategy is None:
-                return attr_prefix + "optimizer"
-            else:
-                return attr_prefix + "{}:restart_{}:optimizer".format(
-                    self._restart_strategy, restart
-                )
-
-        def generation_attr_key_template(restart: int) -> str:
-            if self._restart_strategy is None:
-                return attr_prefix + "generation"
-            else:
-                return attr_prefix + "{}:restart_{}:generation".format(
-                    self._restart_strategy, restart
-                )
-
-        def popsize_attr_key_template() -> str:
-            if self._restart_strategy is None:
-                return attr_prefix + "popsize"
-            else:
-                return attr_prefix + "{}:popsize".format(self._restart_strategy)
-
-        def n_restarts_attr_key_template() -> str:
-            if self._restart_strategy is None:
-                return attr_prefix + "n_restarts"
-            else:
-                return attr_prefix + "{}:n_restarts".format(self._restart_strategy)
-


We could simply remove the _CmaEsAttrKeys class and return a string object, since all callable functions have been removed in this PR. This could be addressed in a follow-up PR.

Thank you for the suggestion. I created the follow-up PR, #6068

sawa3030 added 4 commits March 28, 2025 18:12

remove restart_strategy and inc_popsize

f170841

minor change

ced21c7

add deprecation warning

73d376d

minor change

c66fdb8

sawa3030 marked this pull request as ready for review April 4, 2025 06:07

update docstring

50dfc9e

y0z added the compatibility Change that breaks compatibility. label Apr 7, 2025

y0z assigned c-bata and HideakiImamura Apr 7, 2025

sawa3030 mentioned this pull request Apr 9, 2025

Add RestartCmaEs optuna/optunahub-registry#261

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HideakiImamura reviewed Apr 10, 2025

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sawa3030 added 2 commits April 11, 2025 00:20

update docstring and popsize behavior

44a802b

minor change

c7c14e7

nabenabe0928 added this to the v4.4.0 milestone Apr 16, 2025

HideakiImamura reviewed Apr 18, 2025

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minor change

d70218d

c-bata reviewed Apr 21, 2025

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HideakiImamura reviewed Apr 23, 2025

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sawa3030 force-pushed the deprecate-restart-strategy branch from 8dc9671 to a87d238 Compare April 25, 2025 05:55

sawa3030 added 2 commits April 25, 2025 15:45

adress comment

8dab48d

Revert "adress comment"

0245e8c

This reverts commit 8dab48d.

sawa3030 force-pushed the deprecate-restart-strategy branch from a87d238 to 0245e8c Compare April 25, 2025 06:47

sawa3030 added 5 commits April 25, 2025 16:56

update docstring

b3719c3

minor change

312d88b

minor change

da62f02

update _init_optimizer

8b26669

remove setting popsize when it is None

a927f45

use optimizer.population_size

f3e52c0

HideakiImamura approved these changes Apr 30, 2025

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HideakiImamura removed their assignment May 1, 2025

c-bata approved these changes May 1, 2025

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c-bata merged commit ddcc20e into optuna:master May 1, 2025
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This was referenced May 2, 2025

Remove CmaEsAttrKeys and _attr_keys for Simplification #6068

Merged

Remove Unrelated Options from RestartCmaEsSampler for Simplification optuna/optunahub-registry#266

Merged

sawa3030 mentioned this pull request May 16, 2025

Store optimizer state in memory to improve CmaEsSampler performance optuna/optunahub-registry#269

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sawa3030 deleted the deprecate-restart-strategy branch November 14, 2025 07:46

	Deprecated in v4.3.0. ``consider_prior`` argument will be removed in the future.
	Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.

	See https://github.com/optuna/optuna/releases/tag/v4.3.0.
	See https://github.com/optuna/optuna/releases/tag/v4.4.0.

	name="`restart_strategy`", d_ver="4.3.0", r_ver="6.0.0"
	name="`restart_strategy`", d_ver="4.4.0", r_ver="6.0.0"

	if restart_strategy is not None or inc_popsize != 2:
	if restart_strategy is not None or inc_popsize != -1:

	optimizer = self._init_optimizer(trans, study.direction, population_size=self._popsize)
	optimizer = self._init_optimizer(trans, study.direction)

		if self._popsize is None:
		self._popsize = 4 + math.floor(3 * math.log(len(trans.bounds)))

	Deprecated in v4.4.0. ``restart_strategy`` argument will be removed in the future.
	Deprecated in v4.4.0. ``inc_popsize`` argument will be removed in the future.

		From v4.4.0 onward, ``restart_strategy`` automatically falls back to ``None``, and
		``restart_strategy`` will be supported in OptunaHub.

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sawa3030 commented Mar 28, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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sawa3030 commented Mar 28, 2025 •

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