{"action":"created","issue":{"url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/82","repository_url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl","labels_url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/82/labels{/name}","comments_url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/82/comments","events_url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/82/events","html_url":"https://github.com/JuliaNLSolvers/Manifolds.jl/pull/82","id":544305826,"node_id":"MDExOlB1bGxSZXF1ZXN0MzU4NDQ3NDYw","number":82,"title":"[WIP] Add semidirect product group","user":{"login":"sethaxen","id":8673634,"node_id":"MDQ6VXNlcjg2NzM2MzQ=","avatar_url":"https://avatars3.githubusercontent.com/u/8673634?v=4","gravatar_id":"","url":"https://api.github.com/users/sethaxen","html_url":"https://github.com/sethaxen","followers_url":"https://api.github.com/users/sethaxen/followers","following_url":"https://api.github.com/users/sethaxen/following{/other_user}","gists_url":"https://api.github.com/users/sethaxen/gists{/gist_id}","starred_url":"https://api.github.com/users/sethaxen/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sethaxen/subscriptions","organizations_url":"https://api.github.com/users/sethaxen/orgs","repos_url":"https://api.github.com/users/sethaxen/repos","events_url":"https://api.github.com/users/sethaxen/events{/privacy}","received_events_url":"https://api.github.com/users/sethaxen/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":3,"created_at":"2020-01-01T03:43:19Z","updated_at":"2020-01-02T08:28:15Z","closed_at":null,"author_association":"COLLABORATOR","pull_request":{"url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/pulls/82","html_url":"https://github.com/JuliaNLSolvers/Manifolds.jl/pull/82","diff_url":"https://github.com/JuliaNLSolvers/Manifolds.jl/pull/82.diff","patch_url":"https://github.com/JuliaNLSolvers/Manifolds.jl/pull/82.patch"},"body":"Following up #68, this PR implements some of the suggestions in #81. And since we now have actions on groups, this PR implements the semidirect product group, which is just an alias for a `GroupManifold` with a `SemidirectProductOperation`, which wraps two groups and an action by one group on the other. A simple example is given using `SpecialEuclidean(N)`.\r\n\r\nThis PR doesn't yet add any tests, and it breaks some old tests.\r\n\r\nI haven't figured out how to implement the differential of right translation for the semidirect product group, but I'm also not convinced that the current differential code does what it says it does (I think it came from my old PR #25). @mateuszbaran do you have a use case for the differentials? I'm not certain why I implemented them. 🙂 "},"comment":{"url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/comments/570143595","html_url":"https://github.com/JuliaNLSolvers/Manifolds.jl/pull/82#issuecomment-570143595","issue_url":"https://api.github.com/repos/JuliaNLSolvers/Manifolds.jl/issues/82","id":570143595,"node_id":"MDEyOklzc3VlQ29tbWVudDU3MDE0MzU5NQ==","user":{"login":"mateuszbaran","id":2551062,"node_id":"MDQ6VXNlcjI1NTEwNjI=","avatar_url":"https://avatars2.githubusercontent.com/u/2551062?v=4","gravatar_id":"","url":"https://api.github.com/users/mateuszbaran","html_url":"https://github.com/mateuszbaran","followers_url":"https://api.github.com/users/mateuszbaran/followers","following_url":"https://api.github.com/users/mateuszbaran/following{/other_user}","gists_url":"https://api.github.com/users/mateuszbaran/gists{/gist_id}","starred_url":"https://api.github.com/users/mateuszbaran/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mateuszbaran/subscriptions","organizations_url":"https://api.github.com/users/mateuszbaran/orgs","repos_url":"https://api.github.com/users/mateuszbaran/repos","events_url":"https://api.github.com/users/mateuszbaran/events{/privacy}","received_events_url":"https://api.github.com/users/mateuszbaran/received_events","type":"User","site_admin":false},"created_at":"2020-01-02T08:28:15Z","updated_at":"2020-01-02T08:28:15Z","author_association":"COLLABORATOR","body":"Yes, right, differentials for these left translations should be a no-op for `SpecialOrthogonal` and `transpose(x) * v * x` looks right for the right translation. I think it's a good idea then to just remove these definitions for differentials on abstract group operations and leave just the correct implementations for specific groups. The scaling group is also multiplicative but has a different differential for example."}}
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