This is the release note of v4.7.0.

Highlights

Two New Multi-Objective Samplers Added to OptunaHub!

@hrntsm introduces two new multi-objective samplers—SPEA-II (Strength Pareto Evolutionary Algorithm 2) and HypE (Hypervolume Estimation Algorithm)—to OptunaHub. SPEA-II is an improved multi-objective evolutionary algorithm that differs from NSGA-II in its selection mechanism. HypE is a fast, hypervolume-based evolutionary algorithm designed for many-objective optimization problems. Please refer to the following pages for more details:

• SPEA-II: https://hub.optuna.org/samplers/speaii/
• HypE: https://hub.optuna.org/samplers/hype/

PedAnovaImportanceEvaluator Now Supports Local Hyperparameter Importance Computation

The target_quantile and region_quantile arguments have been introduced to PedAnovaImportanceEvaluator. This change allows you to investigate local hyperparameter importance rather than the global one with region_quantile < 1.0. See the original paper for the technical details.

Enhancements

• Introduce stacklevel-aware custom warnings (#6293)
• Cache distributions to skip consistency check (#6301)
• Add warnings when JournalStorage lock acquisition is delayed (#6361)
• Add support for local HPI in PED-ANOVA (#6362)

Bug Fixes

• Fix log PDF of discrete trunc log-norm distribution for TPESampler (#6258)
• Fix coefficient in PED-ANOVA (#6358)
• Fix GPSampler crash when default torch device is CUDA (#6397, thanks @Quant-Quasar!)

Documentation

• Add SECURITY.md (#6317)
• Add a note for future dev of exclusive HV (#6318)
• Update GPSampler documentation to include D-BE optimization details (#6347, thanks @Kaichi-Irie!)
• Revert PR #6354 to enable -W option on Sphinx build (#6373)

Examples

• Disable scheduled runs for PyTorch and visualization temporarily (optuna/optuna-examples#337)
• Fix skorch example: Replace unavailable OpenML MNIST (optuna/optuna-examples#338, thanks @sotagg!)
• Pin minio version to <=7.2.18 to fix CI & stop daily CI running (optuna/optuna-examples#339)
• fix spark example (optuna/optuna-examples#342, thanks @fritshermans!)
• Pin scikit-learn to < 1.6.0 for lightgbm (optuna/optuna-examples#343)
• Remove python 3.9 due to EOL Status (optuna/optuna-examples#344, thanks @ParagEkbote!)
• Add IPython as a dependency of fastai example (optuna/optuna-examples#347)

Tests

• Fix TC006 violation in tests/visualization_tests/test_utils.py (#6387, thanks @jiayusu!)

Code Fixes

• Replace .format() with f-string in _setup_studies (#6326, thanks @haitham404!)
• Update _upload.py for TYPE_CHECKING (#6327, thanks @satyarth7srivastava!)
• Replace .format() with f-string in progress_bar.py (#6328, thanks @Nayil97!)
• Use f-strings in optuna/samplers/_cmaes.py (#6331, thanks @swativdusane!)
• Replace .format() with f-string in _parallel_coordinate.py (#6333, thanks @satyarth7srivastava!)
• Refactor/fstring storage rdb (#6336, thanks @gadmin7!)
• Migrate to ruff from black/blackdoc/isort/flake8 (#6341)
• Replace .format with f-strings in optuna/importance/_base (#6342, thanks @VihaanMotwani!)
• updated _terminator_improvement.py for TYPE_CHECKING (#6343, thanks @satyarth7srivastava!)
• Replace .format with f-string in _param_importances.py (#6345, thanks @Harshadev-24!)
• Replace .format() with f-strings in several modules (#6348, thanks @varundevr!)
• Replace more .format() calls with f-strings (#6349, thanks @varundevr!)
• Replace .format with f-string in tutorial/20_recipes/004_cli.py (#6350, thanks @RektPunk!)
• Replace .format with f-string in optuna/study/_optimize.py (#6351, thanks @RektPunk!)
• Format optuna/ files with Ruff (#6352)
• Refactor: Use f-string in 001_rdb.py (#6356, thanks @sotagg!)
• Format tests/ and tutorials/ files with Ruff (#6360)
• Remove redundant _color_supported() check (#6363)
• Add StorageTestCase class in optuna.testing package (#6369)
• Change string formatting in optuna/pruners/_hyperband.py (#6370, thanks @eleannapapaio!)
• Refactor test_study.py to use f-string instead of .format() (#6372, thanks @nepersoned!)
• Fix mypy error for np.select (#6374)
• Change string formatting for _successive_halving.py (#6375, thanks @spenam!)
• Fix type annotations for optuna/trial/_frozen.py (#6377, thanks @spenam!)
• fix type annotations for optuna/study/study.py (#6378, thanks @spenam!)
• Fix type annotations for tests/study_tests/test_study.py (#6379, thanks @spenam!)
• Move type-only imports to TYPE_CHECKING in test_visualizations.py (#6380, thanks @Sip4818!)
• Move type-only imports to TYPE_CHECKING in _constrained_optimization.py (#6381, thanks @Sip4818!)
• Replace format with f-string (#6383, thanks @varundevr!)
• Move type-only imports to TYPE_CHECKING in _multi_objective.py (#6385, thanks @Sip4818!)
• Move FrozenTrial import under TYPE_CHECKING for _study_summary.py file (#6386, thanks @Sip4818!)
• Move type-check imports to TYPE_CHECKING in optuna/terminator/callback.py (#6388, thanks @Sip4818!)
• Using f-string instead of .format() (#6389, thanks @Lakshman142!)
• Use f-strings in optuna/_experimental.py (#6390, thanks @Rohan0497!)
• Fix invalid StorageTestCase scenarios involving trial state and values (#6391)
• Move type-hint import inside Type-Checking block in optuna\terminator\erroreval.py (#6395, thanks @Sip4818!)
• Move type-check imports to TYPE_CHECKING in optuna\terminator\improvement\emmr.py (#6396, thanks @Sip4818!)
• Move typing-only imports under TYPE_CHECKING in matplotlib/_slice.py (#6399, thanks @kapishyadav!)
• Use logger.warning instead of optuna_warn for lock-acquisition delay notifications (#6400)
• Update string formatting in optuna/samplers/_grid.py (#6401, thanks @kapishyadav!)
• Updating storages/_in_memory.py to use f-strings (#6404, thanks @jrings!)
• Move type-hint imports into type-checking block in optuna\terminator\improvement\evaluator.py (#6405, thanks @Sip4818!)
• Move type-hint imports into type-checking block in median_erroreval.py (#6408, thanks @Sip4818!)
• Replace .format() with f-string in _rank.py (#6409, thanks @jwalith!)
• Replace .format() with f-string in test_hyperband.py (#6411, thanks @Banjiola!)
• Replace .format() with f-string in _fixed.py (#6412, thanks @VedantMadane!)

Continuous Integration

• Fix for CI (optuna/optuna-integration#258)
• Add ipython as a dependency of fastai (optuna/optuna-integration#261)
• Remove FastAIV2PruningCallback from docs to resolve warning (optuna/optuna-integration#264)
• Dispose SQLAlchemy's engine in storage_tests/test_with_server.py (#6330)
• Dispose SQLAlchemy's engine in storage_tests/test_cached_storage.py (#6337)
• Dispose SQLAlchemy's engine in storage_tests/rdb_tests/test_storage.py (#6338)
• Support Python 3.14 (#6339)
• Temporarily disable -W option on Sphinx build (#6354)

Other

• Bump up version (optuna/optuna-integration#256)
• Bump up version number to 4.7.0 (optuna/optuna-integration#262)
• Bump up to the version number v4.7.0.dev (#6325)
• Update the news section on README (#6335)
• Remove Codecov usage (#6340)
• Remove formats.sh and tidy up CONTRIBUTING.md (#6353)
• Remove asv and the speed benchmark workflow (#6393)
• Bump up version to v4.7.0 (#6413)

Thanks to All the Contributors!

This release was made possible by the authors and the people who participated in the reviews and discussions.

@Alnusjaponica, @Banjiola, @Harshadev-24, @HideakiImamura, @Kaichi-Irie, @Lakshman142, @Nayil97, @ParagEkbote, @Quant-Quasar, @RektPunk, @Rohan0497, @Sip4818, @VedantMadane, @VihaanMotwani, @c-bata, @eleannapapaio, @fritshermans, @fusawa-yugo, @gadmin7, @gen740, @haitham404, @jiayusu, @jrings, @jwalith, @kAIto47802, @kapishyadav, @nabenabe0928, @nepersoned, @not522, @nzw0301, @satyarth7srivastava, @sawa3030, @sotagg, @spenam, @swativdusane, @toshihikoyanase, @varundevr, @y0z