{"action":"opened","issue":{"url":"https://api.github.com/repos/nikomatsakis/rayon/issues/49","repository_url":"https://api.github.com/repos/nikomatsakis/rayon","labels_url":"https://api.github.com/repos/nikomatsakis/rayon/issues/49/labels{/name}","comments_url":"https://api.github.com/repos/nikomatsakis/rayon/issues/49/comments","events_url":"https://api.github.com/repos/nikomatsakis/rayon/issues/49/events","html_url":"https://github.com/nikomatsakis/rayon/issues/49","id":131960092,"number":49,"title":"Change default weight of parallel iterators to assume expensive ops","user":{"login":"nikomatsakis","id":155238,"avatar_url":"https://avatars.githubusercontent.com/u/155238?v=3","gravatar_id":"","url":"https://api.github.com/users/nikomatsakis","html_url":"https://github.com/nikomatsakis","followers_url":"https://api.github.com/users/nikomatsakis/followers","following_url":"https://api.github.com/users/nikomatsakis/following{/other_user}","gists_url":"https://api.github.com/users/nikomatsakis/gists{/gist_id}","starred_url":"https://api.github.com/users/nikomatsakis/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nikomatsakis/subscriptions","organizations_url":"https://api.github.com/users/nikomatsakis/orgs","repos_url":"https://api.github.com/users/nikomatsakis/repos","events_url":"https://api.github.com/users/nikomatsakis/events{/privacy}","received_events_url":"https://api.github.com/users/nikomatsakis/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2016-02-07T11:25:53Z","updated_at":"2016-02-07T11:25:53Z","closed_at":null,"body":"Currently parallel iterators assume cheap operations. I am thinking that should be changed to assume expensive operations (i.e., fine-grained parallel splits), and have people opt-in to the current behavior by manually adjusting the weights or calling `weight_min`. My reasoning is:\r\n\r\n1. The worst case behavior today is that you don't see any parallel speedup, which sucks. I see a lot of questions bout this.\r\n2. The worst case behavior with the new default would be that you see less speedup than you expected. If we do a good job optimizing, this should be fairly low.\r\n3. It seems to be what I want more often.\r\n\r\nThoughts?"}}