{"action":"created","issue":{"url":"https://api.github.com/repos/dealii/dealii/issues/448","labels_url":"https://api.github.com/repos/dealii/dealii/issues/448/labels{/name}","comments_url":"https://api.github.com/repos/dealii/dealii/issues/448/comments","events_url":"https://api.github.com/repos/dealii/dealii/issues/448/events","html_url":"https://github.com/dealii/dealii/pull/448","id":54629535,"number":448,"title":"[RFC] Add a testcase that current fails.","user":{"login":"bangerth","id":7504421,"avatar_url":"https://avatars.githubusercontent.com/u/7504421?v=3","gravatar_id":"","url":"https://api.github.com/users/bangerth","html_url":"https://github.com/bangerth","followers_url":"https://api.github.com/users/bangerth/followers","following_url":"https://api.github.com/users/bangerth/following{/other_user}","gists_url":"https://api.github.com/users/bangerth/gists{/gist_id}","starred_url":"https://api.github.com/users/bangerth/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bangerth/subscriptions","organizations_url":"https://api.github.com/users/bangerth/orgs","repos_url":"https://api.github.com/users/bangerth/repos","events_url":"https://api.github.com/users/bangerth/events{/privacy}","received_events_url":"https://api.github.com/users/bangerth/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2015-01-16T21:52:26Z","updated_at":"2015-01-17T00:07:10Z","closed_at":null,"pull_request":{"url":"https://api.github.com/repos/dealii/dealii/pulls/448","html_url":"https://github.com/dealii/dealii/pull/448","diff_url":"https://github.com/dealii/dealii/pull/448.diff","patch_url":"https://github.com/dealii/dealii/pull/448.patch"},"body":"This shows a failure inside Trilinos's AztecOO package when one tries to solve\r\na linear system with a perfectly SPD matrix and a preset solution vector (the\r\nproblem does not occur when the solution vector is not preset). With the preset\r\nsolution, we get this error:\r\n\r\n1: --------------------------------------------------------\r\n1: An error occurred in line <282> of file </u/bangerth/p/deal.II/1/dealii/source/lac/trilinos_solver.cc> in function\r\n1:     void dealii::TrilinosWrappers::SolverBase::do_solve(const dealii::TrilinosWrappers::PreconditionBase&)\r\n1: The violated condition was:\r\n1:     false\r\n1: The name and call sequence of the exception was:\r\n1:     ExcMessage('AztecOO::Iterate error code -3: ' 'loss of precision')\r\n1: Additional Information:\r\n1: AztecOO::Iterate error code -3: loss of precision\r\n1: --------------------------------------------------------"},"comment":{"url":"https://api.github.com/repos/dealii/dealii/issues/comments/70342784","html_url":"https://github.com/dealii/dealii/pull/448#issuecomment-70342784","issue_url":"https://api.github.com/repos/dealii/dealii/issues/448","id":70342784,"user":{"login":"bangerth","id":7504421,"avatar_url":"https://avatars.githubusercontent.com/u/7504421?v=3","gravatar_id":"","url":"https://api.github.com/users/bangerth","html_url":"https://github.com/bangerth","followers_url":"https://api.github.com/users/bangerth/followers","following_url":"https://api.github.com/users/bangerth/following{/other_user}","gists_url":"https://api.github.com/users/bangerth/gists{/gist_id}","starred_url":"https://api.github.com/users/bangerth/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bangerth/subscriptions","organizations_url":"https://api.github.com/users/bangerth/orgs","repos_url":"https://api.github.com/users/bangerth/repos","events_url":"https://api.github.com/users/bangerth/events{/privacy}","received_events_url":"https://api.github.com/users/bangerth/received_events","type":"User","site_admin":false},"created_at":"2015-01-17T00:07:10Z","updated_at":"2015-01-17T00:07:10Z","body":"I tried multiplying the rhs and preset solution by 1e12 and it didn't make a difference (as it should). Machine precision is only relevant in a relative sense, so I don't think it should matter here.\r\n\r\nBut so you're saying that you get a regular iteration failure, not the AztecOO message? What Trilinos version are you working with?"}}