{"action":"opened","issue":{"url":"https://api.github.com/repos/pyqg/pyqg/issues/144","repository_url":"https://api.github.com/repos/pyqg/pyqg","labels_url":"https://api.github.com/repos/pyqg/pyqg/issues/144/labels{/name}","comments_url":"https://api.github.com/repos/pyqg/pyqg/issues/144/comments","events_url":"https://api.github.com/repos/pyqg/pyqg/issues/144/events","html_url":"https://github.com/pyqg/pyqg/issues/144","id":146483504,"number":144,"title":"Automatic / Adaptive Timestepping","user":{"login":"rabernat","id":1197350,"avatar_url":"https://avatars.githubusercontent.com/u/1197350?v=3","gravatar_id":"","url":"https://api.github.com/users/rabernat","html_url":"https://github.com/rabernat","followers_url":"https://api.github.com/users/rabernat/followers","following_url":"https://api.github.com/users/rabernat/following{/other_user}","gists_url":"https://api.github.com/users/rabernat/gists{/gist_id}","starred_url":"https://api.github.com/users/rabernat/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rabernat/subscriptions","organizations_url":"https://api.github.com/users/rabernat/orgs","repos_url":"https://api.github.com/users/rabernat/repos","events_url":"https://api.github.com/users/rabernat/events{/privacy}","received_events_url":"https://api.github.com/users/rabernat/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/pyqg/pyqg/labels/enhancement","name":"enhancement","color":"84b6eb"},{"url":"https://api.github.com/repos/pyqg/pyqg/labels/performance","name":"performance","color":"fbca04"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2016-04-07T01:35:11Z","updated_at":"2016-04-07T01:35:11Z","closed_at":null,"body":"Currently the timestep is set manually. This is both a challenge for novice users (how do you know how to pick) and a major performance bottleneck (if the timestep is unnecessarily small). \r\n\r\nWe should make the timestep choice automatic based on a target CFL condition. I found some nice documentation about how to do this with Adams Bashforth.\r\n\r\nhttp://lucan.me.jhu.edu/wiki/index.php/The_flow_solver_implementation#Adaptive_time_stepping\r\nhttp://lucan.me.jhu.edu/wiki/index.php/Second-order_variable_time_step_Adams-Bashforth_method\r\n"}}