The bulk of the review for O4 is focusing on sampler settings that give good performance on the expected CBC population. See [this wiki](https://git.ligo.org/pe/O4/bilby_o4_review/-/wikis/home) for more details.
There are a few significant code changes that need review/review documentation though. This wiki is intended to provide a home for these things.
Many of these features have unit tests verifying their performance, others have dedicated review wikis.
## Significant changes
- Optimized Cython geometric functions: [bilby-cython](https://git.ligo.org/colm.talbot/bilby-cython) is reviewed in [issues](https://git.ligo.org/colm.talbot/bilby-cython/-/issues/?sort=updated_desc&state=closed&first_page_size=20).
- Sampling in aligned and planar spin components (https://git.ligo.org/lscsoft/bilby/-/merge_requests/868)
- Various improvements to ROQ likelihood (https://git.ligo.org/lscsoft/bilby/-/merge_requests/1093, https://git.ligo.org/lscsoft/bilby/-/merge_requests/1216, https://git.ligo.org/lscsoft/bilby/-/merge_requests/1196)
