{"action":"created","issue":{"url":"https://api.github.com/repos/JuliaLang/julia/issues/15131","repository_url":"https://api.github.com/repos/JuliaLang/julia","labels_url":"https://api.github.com/repos/JuliaLang/julia/issues/15131/labels{/name}","comments_url":"https://api.github.com/repos/JuliaLang/julia/issues/15131/comments","events_url":"https://api.github.com/repos/JuliaLang/julia/issues/15131/events","html_url":"https://github.com/JuliaLang/julia/issues/15131","id":134532821,"number":15131,"title":"Schur factorization slow as compared to Octave","user":{"login":"ranjanan","id":9101377,"avatar_url":"https://avatars.githubusercontent.com/u/9101377?v=3","gravatar_id":"","url":"https://api.github.com/users/ranjanan","html_url":"https://github.com/ranjanan","followers_url":"https://api.github.com/users/ranjanan/followers","following_url":"https://api.github.com/users/ranjanan/following{/other_user}","gists_url":"https://api.github.com/users/ranjanan/gists{/gist_id}","starred_url":"https://api.github.com/users/ranjanan/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ranjanan/subscriptions","organizations_url":"https://api.github.com/users/ranjanan/orgs","repos_url":"https://api.github.com/users/ranjanan/repos","events_url":"https://api.github.com/users/ranjanan/events{/privacy}","received_events_url":"https://api.github.com/users/ranjanan/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/JuliaLang/julia/labels/linear%20algebra","name":"linear algebra","color":"aa8800"},{"url":"https://api.github.com/repos/JuliaLang/julia/labels/performance","name":"performance","color":"d7e102"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2016-02-18T09:58:52Z","updated_at":"2016-02-18T10:37:23Z","closed_at":null,"body":"On MacOSX, the schur factorization is slower on Julia than on Octave. For a matrix of size 1500 x 1500,\r\n\r\n```\r\noctave:5> tic; [U,S] = schur(a); toc;\r\nElapsed time is 4.69628 seconds.\r\n```\r\nand Julia v0.4.1\r\n```\r\njulia> @time schur(a);\r\n  6.623093 seconds (33 allocations: 34.772 MB, 1.30% gc time)\r\n```\r\nHowever, if you build Julia with system BLAS, which uses Apple's Accelerate, you get better performance:\r\n```\r\njulia> @time schur(a);\r\n  3.334246 seconds (43 allocations: 34.773 MB, 0.10% gc time)\r\n```\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/JuliaLang/julia/issues/comments/185646182","html_url":"https://github.com/JuliaLang/julia/issues/15131#issuecomment-185646182","issue_url":"https://api.github.com/repos/JuliaLang/julia/issues/15131","id":185646182,"user":{"login":"tkelman","id":5934628,"avatar_url":"https://avatars.githubusercontent.com/u/5934628?v=3","gravatar_id":"","url":"https://api.github.com/users/tkelman","html_url":"https://github.com/tkelman","followers_url":"https://api.github.com/users/tkelman/followers","following_url":"https://api.github.com/users/tkelman/following{/other_user}","gists_url":"https://api.github.com/users/tkelman/gists{/gist_id}","starred_url":"https://api.github.com/users/tkelman/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/tkelman/subscriptions","organizations_url":"https://api.github.com/users/tkelman/orgs","repos_url":"https://api.github.com/users/tkelman/repos","events_url":"https://api.github.com/users/tkelman/events{/privacy}","received_events_url":"https://api.github.com/users/tkelman/received_events","type":"User","site_admin":false},"created_at":"2016-02-18T10:37:23Z","updated_at":"2016-02-18T10:37:23Z","body":"Same guess as in https://github.com/JuliaLang/julia/issues/5728#issuecomment-185518733. If openblas built with icc and ifort is as fast as MKL, we have our answer and can file a bug with gfortran."}}