{"action":"closed","issue":{"url":"https://api.github.com/repos/JuliaDiffEq/OrdinaryDiffEq.jl/issues/538","repository_url":"https://api.github.com/repos/JuliaDiffEq/OrdinaryDiffEq.jl","labels_url":"https://api.github.com/repos/JuliaDiffEq/OrdinaryDiffEq.jl/issues/538/labels{/name}","comments_url":"https://api.github.com/repos/JuliaDiffEq/OrdinaryDiffEq.jl/issues/538/comments","events_url":"https://api.github.com/repos/JuliaDiffEq/OrdinaryDiffEq.jl/issues/538/events","html_url":"https://github.com/JuliaDiffEq/OrdinaryDiffEq.jl/issues/538","id":371032175,"node_id":"MDU6SXNzdWUzNzEwMzIxNzU=","number":538,"title":"Callback with zero time does not rollback integrator","user":{"login":"pengwyn","id":31554,"node_id":"MDQ6VXNlcjMxNTU0","avatar_url":"https://avatars1.githubusercontent.com/u/31554?v=4","gravatar_id":"","url":"https://api.github.com/users/pengwyn","html_url":"https://github.com/pengwyn","followers_url":"https://api.github.com/users/pengwyn/followers","following_url":"https://api.github.com/users/pengwyn/following{/other_user}","gists_url":"https://api.github.com/users/pengwyn/gists{/gist_id}","starred_url":"https://api.github.com/users/pengwyn/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/pengwyn/subscriptions","organizations_url":"https://api.github.com/users/pengwyn/orgs","repos_url":"https://api.github.com/users/pengwyn/repos","events_url":"https://api.github.com/users/pengwyn/events{/privacy}","received_events_url":"https://api.github.com/users/pengwyn/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":4,"created_at":"2018-10-17T11:46:10Z","updated_at":"2018-10-19T12:45:29Z","closed_at":"2018-10-19T12:45:28Z","author_association":"NONE","body":"I've been debugging a very rare bug that I have had when using a callback set. I think I've traced it back to the `apply_callback!` function, as it seems as though the variable `cb_time` is not treated properly.\r\n\r\nThe lines in particular are here:\r\nhttps://github.com/JuliaDiffEq/OrdinaryDiffEq.jl/blob/c9910b510c30bdf657d47736ea3086b1f7efc729/src/callbacks.jl#L201-L204\r\n\r\nBasically, if `cb_time == 0` then the function will not roll back the integrator to an earlier time. I have \"fixed\" it temporarily by removing the if test. However, I suspect that wasn't the intention and there was meant to be an `else` block with code to avoid the interpolation and step directly back to `tprev`, `uprev`, etc...\r\n\r\nI would like to make a pull request, reusing a lot of `change_t_via_interpolation!` but avoiding the interpolation itself but I don't know if this is the correct way to do the step back."}}
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