{"action":"opened","number":10280,"pull_request":{"url":"https://api.github.com/repos/sympy/sympy/pulls/10280","id":54050610,"html_url":"https://github.com/sympy/sympy/pull/10280","diff_url":"https://github.com/sympy/sympy/pull/10280.diff","patch_url":"https://github.com/sympy/sympy/pull/10280.patch","issue_url":"https://api.github.com/repos/sympy/sympy/issues/10280","number":10280,"state":"open","locked":false,"title":"Change default value of rref simplify flag to True","user":{"login":"MooVI","id":1942866,"avatar_url":"https://avatars.githubusercontent.com/u/1942866?v=3","gravatar_id":"","url":"https://api.github.com/users/MooVI","html_url":"https://github.com/MooVI","followers_url":"https://api.github.com/users/MooVI/followers","following_url":"https://api.github.com/users/MooVI/following{/other_user}","gists_url":"https://api.github.com/users/MooVI/gists{/gist_id}","starred_url":"https://api.github.com/users/MooVI/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/MooVI/subscriptions","organizations_url":"https://api.github.com/users/MooVI/orgs","repos_url":"https://api.github.com/users/MooVI/repos","events_url":"https://api.github.com/users/MooVI/events{/privacy}","received_events_url":"https://api.github.com/users/MooVI/received_events","type":"User","site_admin":false},"body":"Fixes #10120 . See discussion in that issue. \r\n\r\nTo summarise:\r\n\r\nWithout `simplify=True`, `rref` will silently return wrong results for symbolic matrices. Although simplification is slow, until a better zero-testing method is implemented (which is the real solution, see #10279) the default value of the flag should be true.\r\n\r\nThe other possible solution, put forth by @moorepants is to leave the default value, but have `rref` output a warning when run that if you suspect the results to be wrong to rerun with `simplify=True`.\r\n\r\nI favour changing the default value of the flag because:\r\n\r\na) It is more new-user friendly. Most new users will probably be using small matrices and won't be affected by the slowness of simplification, but will be confused by wrong answers, e.g [this stackoverflow question] (http://stackoverflow.com/questions/19072700/why-does-sympy-give-me-the-wrong-answer-when-i-row-reduce-a-symbolic-matrix). 'Power' users with large expressions are more likely to look at the docs when their code runs slowly.\r\n\r\nb) It is more dev-friendly! Several functions like `gauss_jordan_solve` use `rref` internally. I only ran into this problem because `linear_solve` was not working because the flag was not set correctly. Also, in some functions (which only deal with numerics, say) it might be known that the simplify flag is not needed -- do we then add another to suppress the warning? ","created_at":"2015-12-18T00:22:44Z","updated_at":"2015-12-18T00:22:44Z","closed_at":null,"merged_at":null,"merge_commit_sha":null,"assignee":null,"milestone":null,"commits_url":"https://api.github.com/repos/sympy/sympy/pulls/10280/commits","review_comments_url":"https://api.github.com/repos/sympy/sympy/pulls/10280/comments","review_comment_url":"https://api.github.com/repos/sympy/sympy/pulls/comments{/number}","comments_url":"https://api.github.com/repos/sympy/sympy/issues/10280/comments","statuses_url":"https://api.github.com/repos/sympy/sympy/statuses/607486ea78d2adddeb44ee0ae77085218068ec85","head":{"label":"MooVI:rref-flag","ref":"rref-flag","sha":"607486ea78d2adddeb44ee0ae77085218068ec85","user":{"login":"MooVI","id":1942866,"avatar_url":"https://avatars.githubusercontent.com/u/1942866?v=3","gravatar_id":"","url":"https://api.github.com/users/MooVI","html_url":"https://github.com/MooVI","followers_url":"https://api.github.com/users/MooVI/followers","following_url":"https://api.github.com/users/MooVI/following{/other_user}","gists_url":"https://api.github.com/users/MooVI/gists{/gist_id}","starred_url":"https://api.github.com/users/MooVI/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/MooVI/subscriptions","organizations_url":"https://api.github.com/users/MooVI/orgs","repos_url":"https://api.github.com/users/MooVI/repos","events_url":"https://api.github.com/users/MooVI/events{/privacy}","received_events_url":"https://api.github.com/users/MooVI/received_events","type":"User","site_admin":false},"repo":{"id":46010270,"name":"sympy","full_name":"MooVI/sympy","owner":{"login":"MooVI","id":1942866,"avatar_url":"https://avatars.githubusercontent.com/u/1942866?v=3","gravatar_id":"","url":"https://api.github.com/users/MooVI","html_url":"https://github.com/MooVI","followers_url":"https://api.github.com/users/MooVI/followers","following_url":"https://api.github.com/users/MooVI/following{/other_user}","gists_url":"https://api.github.com/users/MooVI/gists{/gist_id}","starred_url":"https://api.github.com/users/MooVI/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/MooVI/subscriptions","organizations_url":"https://api.github.com/users/MooVI/orgs","repos_url":"https://api.github.com/users/MooVI/repos","events_url":"https://api.github.com/users/MooVI/events{/privacy}","received_events_url":"https://api.github.com/users/MooVI/received_events","type":"User","site_admin":false},"private":false,"html_url":"https://github.com/MooVI/sympy","description":"A computer algebra system written in pure Python","fork":true,"url":"https://api.github.com/repos/MooVI/sympy","forks_url":"https://api.github.com/repos/MooVI/sympy/forks","keys_url":"https://api.github.com/repos/MooVI/sympy/keys{/key_id}","collaborators_url":"https://api.github.com/repos/MooVI/sympy/collaborators{/collaborator}","teams_url":"https://api.github.com/repos/MooVI/sympy/teams","hooks_url":"https://api.github.com/repos/MooVI/sympy/hooks","issue_events_url":"https://api.github.com/repos/MooVI/sympy/issues/events{/number}","events_url":"https://api.github.com/repos/MooVI/sympy/events","assignees_url":"https://api.github.com/repos/MooVI/sympy/assignees{/user}","branches_url":"https://api.github.com/repos/MooVI/sympy/branches{/branch}","tags_url":"https://api.github.com/repos/MooVI/sympy/tags","blobs_url":"https://api.github.com/repos/MooVI/sympy/git/blobs{/sha}","git_tags_url":"https://api.github.com/repos/MooVI/sympy/git/tags{/sha}","git_refs_url":"https://api.github.com/repos/MooVI/sympy/git/refs{/sha}","trees_url":"https://api.github.com/repos/MooVI/sympy/git/trees{/sha}","statuses_url":"https://api.github.com/repos/MooVI/sympy/statuses/{sha}","languages_url":"https://api.github.com/repos/MooVI/sympy/languages","stargazers_url":"https://api.github.com/repos/MooVI/sympy/stargazers","contributors_url":"https://api.github.com/repos/MooVI/sympy/contributors","subscribers_url":"https://api.github.com/repos/MooVI/sympy/subscribers","subscription_url":"https://api.github.com/repos/MooVI/sympy/subscription","commits_url":"https://api.github.com/repos/MooVI/sympy/commits{/sha}","git_commits_url":"https://api.github.com/repos/MooVI/sympy/git/commits{/sha}","comments_url":"https://api.github.com/repos/MooVI/sympy/comments{/number}","issue_comment_url":"https://api.github.com/repos/MooVI/sympy/issues/comments{/number}","contents_url":"https://api.github.com/repos/MooVI/sympy/contents/{+path}","compare_url":"https://api.github.com/repos/MooVI/sympy/compare/{base}...{head}","merges_url":"https://api.github.com/repos/MooVI/sympy/merges","archive_url":"https://api.github.com/repos/MooVI/sympy/{archive_format}{/ref}","downloads_url":"https://api.github.com/repos/MooVI/sympy/downloads","issues_url":"https://api.github.com/repos/MooVI/sympy/issues{/number}","pulls_url":"https://api.github.com/repos/MooVI/sympy/pulls{/number}","milestones_url":"https://api.github.com/repos/MooVI/sympy/milestones{/number}","notifications_url":"https://api.github.com/repos/MooVI/sympy/notifications{?since,all,participating}","labels_url":"https://api.github.com/repos/MooVI/sympy/labels{/name}","releases_url":"https://api.github.com/repos/MooVI/sympy/releases{/id}","created_at":"2015-11-11T21:14:31Z","updated_at":"2015-11-11T21:14:44Z","pushed_at":"2015-12-18T00:20:21Z","git_url":"git://github.com/MooVI/sympy.git","ssh_url":"git@github.com:MooVI/sympy.git","clone_url":"https://github.com/MooVI/sympy.git","svn_url":"https://github.com/MooVI/sympy","homepage":"http://sympy.org/","size":73202,"stargazers_count":0,"watchers_count":0,"language":"Python","has_issues":false,"has_downloads":true,"has_wiki":true,"has_pages":false,"forks_count":0,"mirror_url":null,"open_issues_count":0,"forks":0,"open_issues":0,"watchers":0,"default_branch":"master"}},"base":{"label":"sympy:master","ref":"master","sha":"d665df5135c02211156d4b7a886a2ebae970c10f","user":{"login":"sympy","id":260832,"avatar_url":"https://avatars.githubusercontent.com/u/260832?v=3","gravatar_id":"","url":"https://api.github.com/users/sympy","html_url":"https://github.com/sympy","followers_url":"https://api.github.com/users/sympy/followers","following_url":"https://api.github.com/users/sympy/following{/other_user}","gists_url":"https://api.github.com/users/sympy/gists{/gist_id}","starred_url":"https://api.github.com/users/sympy/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sympy/subscriptions","organizations_url":"https://api.github.com/users/sympy/orgs","repos_url":"https://api.github.com/users/sympy/repos","events_url":"https://api.github.com/users/sympy/events{/privacy}","received_events_url":"https://api.github.com/users/sympy/received_events","type":"Organization","site_admin":false},"repo":{"id":640534,"name":"sympy","full_name":"sympy/sympy","owner":{"login":"sympy","id":260832,"avatar_url":"https://avatars.githubusercontent.com/u/260832?v=3","gravatar_id":"","url":"https://api.github.com/users/sympy","html_url":"https://github.com/sympy","followers_url":"https://api.github.com/users/sympy/followers","following_url":"https://api.github.com/users/sympy/following{/other_user}","gists_url":"https://api.github.com/users/sympy/gists{/gist_id}","starred_url":"https://api.github.com/users/sympy/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sympy/subscriptions","organizations_url":"https://api.github.com/users/sympy/orgs","repos_url":"https://api.github.com/users/sympy/repos","events_url":"https://api.github.com/users/sympy/events{/privacy}","received_events_url":"https://api.github.com/users/sympy/received_events","type":"Organization","site_admin":false},"private":false,"html_url":"https://github.com/sympy/sympy","description":"A computer algebra system written in pure Python","fork":false,"url":"https://api.github.com/repos/sympy/sympy","forks_url":"https://api.github.com/repos/sympy/sympy/forks","keys_url":"https://api.github.com/repos/sympy/sympy/keys{/key_id}","collaborators_url":"https://api.github.com/repos/sympy/sympy/collaborators{/collaborator}","teams_url":"https://api.github.com/repos/sympy/sympy/teams","hooks_url":"https://api.github.com/repos/sympy/sympy/hooks","issue_events_url":"https://api.github.com/repos/sympy/sympy/issues/events{/number}","events_url":"https://api.github.com/repos/sympy/sympy/events","assignees_url":"https://api.github.com/repos/sympy/sympy/assignees{/user}","branches_url":"https://api.github.com/repos/sympy/sympy/branches{/branch}","tags_url":"https://api.github.com/repos/sympy/sympy/tags","blobs_url":"https://api.github.com/repos/sympy/sympy/git/blobs{/sha}","git_tags_url":"https://api.github.com/repos/sympy/sympy/git/tags{/sha}","git_refs_url":"https://api.github.com/repos/sympy/sympy/git/refs{/sha}","trees_url":"https://api.github.com/repos/sympy/sympy/git/trees{/sha}","statuses_url":"https://api.github.com/repos/sympy/sympy/statuses/{sha}","languages_url":"https://api.github.com/repos/sympy/sympy/languages","stargazers_url":"https://api.github.com/repos/sympy/sympy/stargazers","contributors_url":"https://api.github.com/repos/sympy/sympy/contributors","subscribers_url":"https://api.github.com/repos/sympy/sympy/subscribers","subscription_url":"https://api.github.com/repos/sympy/sympy/subscription","commits_url":"https://api.github.com/repos/sympy/sympy/commits{/sha}","git_commits_url":"https://api.github.com/repos/sympy/sympy/git/commits{/sha}","comments_url":"https://api.github.com/repos/sympy/sympy/comments{/number}","issue_comment_url":"https://api.github.com/repos/sympy/sympy/issues/comments{/number}","contents_url":"https://api.github.com/repos/sympy/sympy/contents/{+path}","compare_url":"https://api.github.com/repos/sympy/sympy/compare/{base}...{head}","merges_url":"https://api.github.com/repos/sympy/sympy/merges","archive_url":"https://api.github.com/repos/sympy/sympy/{archive_format}{/ref}","downloads_url":"https://api.github.com/repos/sympy/sympy/downloads","issues_url":"https://api.github.com/repos/sympy/sympy/issues{/number}","pulls_url":"https://api.github.com/repos/sympy/sympy/pulls{/number}","milestones_url":"https://api.github.com/repos/sympy/sympy/milestones{/number}","notifications_url":"https://api.github.com/repos/sympy/sympy/notifications{?since,all,participating}","labels_url":"https://api.github.com/repos/sympy/sympy/labels{/name}","releases_url":"https://api.github.com/repos/sympy/sympy/releases{/id}","created_at":"2010-04-30T20:37:14Z","updated_at":"2015-12-17T09:55:59Z","pushed_at":"2015-12-18T00:00:50Z","git_url":"git://github.com/sympy/sympy.git","ssh_url":"git@github.com:sympy/sympy.git","clone_url":"https://github.com/sympy/sympy.git","svn_url":"https://github.com/sympy/sympy","homepage":"http://sympy.org/","size":103102,"stargazers_count":2514,"watchers_count":2514,"language":"Python","has_issues":true,"has_downloads":true,"has_wiki":true,"has_pages":false,"forks_count":1239,"mirror_url":null,"open_issues_count":2090,"forks":1239,"open_issues":2090,"watchers":2514,"default_branch":"master"}},"_links":{"self":{"href":"https://api.github.com/repos/sympy/sympy/pulls/10280"},"html":{"href":"https://github.com/sympy/sympy/pull/10280"},"issue":{"href":"https://api.github.com/repos/sympy/sympy/issues/10280"},"comments":{"href":"https://api.github.com/repos/sympy/sympy/issues/10280/comments"},"review_comments":{"href":"https://api.github.com/repos/sympy/sympy/pulls/10280/comments"},"review_comment":{"href":"https://api.github.com/repos/sympy/sympy/pulls/comments{/number}"},"commits":{"href":"https://api.github.com/repos/sympy/sympy/pulls/10280/commits"},"statuses":{"href":"https://api.github.com/repos/sympy/sympy/statuses/607486ea78d2adddeb44ee0ae77085218068ec85"}},"merged":false,"mergeable":null,"mergeable_state":"unknown","merged_by":null,"comments":0,"review_comments":0,"commits":2,"additions":9,"deletions":7,"changed_files":2}}