{"action":"opened","issue":{"url":"https://api.github.com/repos/nmayorov/bounded-lsq/issues/4","labels_url":"https://api.github.com/repos/nmayorov/bounded-lsq/issues/4/labels{/name}","comments_url":"https://api.github.com/repos/nmayorov/bounded-lsq/issues/4/comments","events_url":"https://api.github.com/repos/nmayorov/bounded-lsq/issues/4/events","html_url":"https://github.com/nmayorov/bounded-lsq/issues/4","id":92431256,"number":4,"title":"ftol termination criterion","user":{"login":"nmayorov","id":7074023,"avatar_url":"https://avatars.githubusercontent.com/u/7074023?v=3","gravatar_id":"","url":"https://api.github.com/users/nmayorov","html_url":"https://github.com/nmayorov","followers_url":"https://api.github.com/users/nmayorov/followers","following_url":"https://api.github.com/users/nmayorov/following{/other_user}","gists_url":"https://api.github.com/users/nmayorov/gists{/gist_id}","starred_url":"https://api.github.com/users/nmayorov/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nmayorov/subscriptions","organizations_url":"https://api.github.com/users/nmayorov/orgs","repos_url":"https://api.github.com/users/nmayorov/repos","events_url":"https://api.github.com/users/nmayorov/events{/privacy}","received_events_url":"https://api.github.com/users/nmayorov/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-07-01T16:43:26Z","updated_at":"2015-07-01T16:43:26Z","closed_at":null,"body":"A quite significant bug was determined recently: if a quadratic local model is strongly inadequate the an algorithm can make a huge step with little or no reduction of the function (jump over a valley) and then terminate by ftol condition.\r\n\r\nI added the additional condition `ratio > 0.25` (which I used originally, but eliminated at some point). MINPACK, on the other hand, checks actual and predicted relative reductions and checks `ratio < 2`. I don't completely understand the purpose of the last check, so I need to think about it. Maybe it's better to adopt MINPACK approach (perhaps ignoring `ratio < 2` if I won't determine its conceptual purpose)."}}