This is the release note of v4.3.0.

Highlights

This has various bug fixes and improvements to the documentation and more.

Breaking Changes

• [fix] lgbm 4.6.0 compatibility (https://github.com/optuna/optuna-integration/pull/207, thanks @ffineis!)

Enhancements

• Accept custom objective in LightGBMTuner (https://github.com/optuna/optuna-integration/pull/203, thanks @sawa3030!)
• Improve time complexity of IntersectionSearchSpace (#5982, thanks @GittyHarsha!)
• Add _prev_waiting_trial_number in InMemoryStorage to improve the efficiency of _pop_waiting_trial_id (#5993, thanks @sawa3030!)
• Add arguments of versions to convert_positional_args (#6009, thanks @fusawa-yugo!)
• Add wait_server_ready method in GrpcStorageProxy (#6010, thanks @hitsgub!)
• Remove warning messages for Matplotlib-based plot_contour and plot_rank (#6011)
• Fix type checking in optuna._callbacks.py (#6030)
• Enhance SBXCrossover (#6008, thanks @hrntsm!)

Bug Fixes

• Convert storage into InMemoryStorage before copying to the local (https://github.com/optuna/optuna-integration/pull/213)
• Fix contour plot of matplotlib (#5892, thanks @fusawa-yugo!)
• Fix threading lock logic (#5922)
• Use _LazyImport for grpcio package (#5954)
• Prevent Lock Blocking by Adding Timeout to JournalStorage (#5971, thanks @sawa3030!)
• Fix a minor bug in GPSampler for objective that returns inf (#5995)
• Fix a bug that a gRPC server doesn't work with JournalStorage (#6004, thanks @fusawa-yugo!)
• Fix _pop_waiting_trial_id for finished trial (#6012)
• Resolve the issue where BruteForceSampler fails to suggest all combinations (#5893)

Documentation

• Follow recent changes in optuna/optuna's document sphinx config (https://github.com/optuna/optuna-integration/pull/197)
• Fix links to external modules (https://github.com/optuna/optuna-integration/pull/198)
• Update CONTRIBUTING.md (https://github.com/optuna/optuna-integration/pull/200, thanks @sawa3030!)
• Update comment in .readthedocs.yml (#5976)
• Add comments on the reproducibility of HyperBandPruner (#6018)

Examples

• [hotfix] Add the version constraint on dask (https://github.com/optuna/optuna-examples/pull/296)
• [hotfix] Add the version constraint on dask for dask-ml (https://github.com/optuna/optuna-examples/pull/297)
• Extends execution span of hiplot and sklearn (https://github.com/optuna/optuna-examples/pull/298, thanks @fusawa-yugo!)
• Apply black to fix CI (https://github.com/optuna/optuna-examples/pull/300)
• Bump up to 3.12 for CI (https://github.com/optuna/optuna-examples/pull/301)
• [hotfix] Add the version constraint on lightgbm (https://github.com/optuna/optuna-examples/pull/302)
• Fix Skorch Example (https://github.com/optuna/optuna-examples/pull/303, thanks @ParagEkbote!)
• Add version constraint for tensorflow-related CI (https://github.com/optuna/optuna-examples/pull/304)
• Temporarily skip Python 3.9 in fastai example (https://github.com/optuna/optuna-examples/pull/308)
• Run the skorch example in the CI (https://github.com/optuna/optuna-examples/pull/309)
• Fix fastai Example (https://github.com/optuna/optuna-examples/pull/312)

Tests

• Use JournalStorage in test_cli.py (#5990, thanks @sawa3030!)

Code Fixes

• Add BaseGASampler (#5864)
• Fix comments in pyproject.toml (#5972)
• Remove FirstTrialOnlyRandomSampler (#5973, thanks @mehakmander11!)
• Remove _check_and_set_param_distribution (#5975, thanks @siddydutta!)
• Remove testing/distributions.py (#5977, thanks @mehakmander11!)
• Remove _StudyInfo's param_distribution in _cached_storage.py (#5978, thanks @tarunprabhu11!)
• Introduce UpdateFinishedTrialError to raise an error when attempting to modify a finished trial (#6001, thanks @sawa3030!)
• Deprecate consider_prior in TPESampler (#6005, thanks @sawa3030!)
• Improve Code Readability by Following PEP8 Standards (#6006, thanks @sawa3030!)
• Made error message for create_study's direction easier to understand optuna.study (#6021, thanks @sinano1107!)

Continuous Integration

• Hotfix ci (https://github.com/optuna/optuna-integration/pull/199)
• Add flake8 in CI (https://github.com/optuna/optuna-integration/pull/201, thanks @sawa3030!)
• Remove test cases that uses UnsupportedDistribution (https://github.com/optuna/optuna-integration/pull/208)
• Fix a mypy error when using numpy>=2.2.4 (https://github.com/optuna/optuna-integration/pull/212)
• Fix a bug of lightgbm tuner for Python 3.8 users (https://github.com/optuna/optuna-integration/pull/214)
• Add a version constraint on xgboost (https://github.com/optuna/optuna-integration/pull/217)
• Run (https://github.com/optuna/optuna-integration/pull/218)
• Ensure gRPC server readiness before proceeding to prevent test failures (#5938, thanks @sawa3030!)
• Apply black to fix CI (#5952)
• Add workflow_dispatch trigger to all the CI (#6019)
• Fix CI (#6026)

Other

• Bump up version number to 4.3.0.dev (https://github.com/optuna/optuna-integration/pull/192)
• Bump the version up to v4.2.1 (https://github.com/optuna/optuna-integration/pull/195)
• Set repository url (https://github.com/optuna/optuna-integration/pull/196, thanks @ktns!)
• Bump up version number to v4.3.0 (https://github.com/optuna/optuna-integration/pull/221)
• Bump the version up to v4.3.0.dev (#5927)
• Add the article to the news section (#5928)
• Update news section for 4.2.0 release (#5934)
• Update News (#5936)
• Update README with the new blog entry (#5980)
• Add GPSampler blog to the announcement (#6014)
• Add grpc blog to README (#6020)

Thanks to All the Contributors!

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

@Alnusjaponica, @GittyHarsha, @HideakiImamura, @ParagEkbote, @c-bata, @contramundum53, @ffineis, @fusawa-yugo, @gen740, @hitsgub, @hrntsm, @kAIto47802, @ktns, @mehakmander11, @nabenabe0928, @not522, @nzw0301, @porink0424, @sawa3030, @siddydutta, @sinano1107, @tarunprabhu11, @toshihikoyanase, @y0z