{"action":"opened","issue":{"url":"https://api.github.com/repos/geodynamics/aspect/issues/282","labels_url":"https://api.github.com/repos/geodynamics/aspect/issues/282/labels{/name}","comments_url":"https://api.github.com/repos/geodynamics/aspect/issues/282/comments","events_url":"https://api.github.com/repos/geodynamics/aspect/issues/282/events","html_url":"https://github.com/geodynamics/aspect/issues/282","id":58725105,"number":282,"title":"Models with constant composition do not converge","user":{"login":"gassmoeller","id":7582930,"avatar_url":"https://avatars.githubusercontent.com/u/7582930?v=3","gravatar_id":"","url":"https://api.github.com/users/gassmoeller","html_url":"https://github.com/gassmoeller","followers_url":"https://api.github.com/users/gassmoeller/followers","following_url":"https://api.github.com/users/gassmoeller/following{/other_user}","gists_url":"https://api.github.com/users/gassmoeller/gists{/gist_id}","starred_url":"https://api.github.com/users/gassmoeller/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/gassmoeller/subscriptions","organizations_url":"https://api.github.com/users/gassmoeller/orgs","repos_url":"https://api.github.com/users/gassmoeller/repos","events_url":"https://api.github.com/users/gassmoeller/events{/privacy}","received_events_url":"https://api.github.com/users/gassmoeller/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-02-24T11:22:13Z","updated_at":"2015-02-24T11:22:13Z","closed_at":null,"body":"The composition solver produces problems for constant compositional fields, because we use the right hand side of the equation for the tolerance computation, which is approximately zero in many of these cases. For now I always use slightly perturbed fields, but for some cases this might not be possible (e.g. if you track the sum of something), and it is nowhere documented that compositional fields should have at least some perturbation, so new users fall into this pit as well.\r\n\r\nAny ideas for a better tolerance computation, or a criterion to skip the solution right away if the new solution would be equal to the old?"}}