{"action":"created","issue":{"url":"https://api.github.com/repos/ddemidov/amgcl/issues/13","labels_url":"https://api.github.com/repos/ddemidov/amgcl/issues/13/labels{/name}","comments_url":"https://api.github.com/repos/ddemidov/amgcl/issues/13/comments","events_url":"https://api.github.com/repos/ddemidov/amgcl/issues/13/events","html_url":"https://github.com/ddemidov/amgcl/issues/13","id":58384343,"number":13,"title":"Parallel versions of Gauss-Seidel","user":{"login":"jdumas","id":578702,"avatar_url":"https://avatars.githubusercontent.com/u/578702?v=3","gravatar_id":"","url":"https://api.github.com/users/jdumas","html_url":"https://github.com/jdumas","followers_url":"https://api.github.com/users/jdumas/followers","following_url":"https://api.github.com/users/jdumas/following{/other_user}","gists_url":"https://api.github.com/users/jdumas/gists{/gist_id}","starred_url":"https://api.github.com/users/jdumas/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jdumas/subscriptions","organizations_url":"https://api.github.com/users/jdumas/orgs","repos_url":"https://api.github.com/users/jdumas/repos","events_url":"https://api.github.com/users/jdumas/events{/privacy}","received_events_url":"https://api.github.com/users/jdumas/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2015-02-20T17:29:56Z","updated_at":"2015-03-03T16:49:34Z","closed_at":null,"body":"Hi,\r\n\r\nHave you considered implementing a parallel version of the Gauss-Seidel relaxation scheme? (so called red-black / multicolor Gauss-Seidel algorithms.) Given the variety of backends I'm not sure this would be easy to do, but I thought I might ask =)\r\n\r\n<bountysource-plugin>\r\n---\r\nWant to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/8753243-parallel-versions-of-gauss-seidel?utm_campaign=plugin&utm_content=tracker%2F790952&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F790952&utm_medium=issues&utm_source=github).\r\n</bountysource-plugin>"},"comment":{"url":"https://api.github.com/repos/ddemidov/amgcl/issues/comments/76984078","html_url":"https://github.com/ddemidov/amgcl/issues/13#issuecomment-76984078","issue_url":"https://api.github.com/repos/ddemidov/amgcl/issues/13","id":76984078,"user":{"login":"jdumas","id":578702,"avatar_url":"https://avatars.githubusercontent.com/u/578702?v=3","gravatar_id":"","url":"https://api.github.com/users/jdumas","html_url":"https://github.com/jdumas","followers_url":"https://api.github.com/users/jdumas/followers","following_url":"https://api.github.com/users/jdumas/following{/other_user}","gists_url":"https://api.github.com/users/jdumas/gists{/gist_id}","starred_url":"https://api.github.com/users/jdumas/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jdumas/subscriptions","organizations_url":"https://api.github.com/users/jdumas/orgs","repos_url":"https://api.github.com/users/jdumas/repos","events_url":"https://api.github.com/users/jdumas/events{/privacy}","received_events_url":"https://api.github.com/users/jdumas/received_events","type":"User","site_admin":false},"created_at":"2015-03-03T16:49:34Z","updated_at":"2015-03-03T16:49:34Z","body":"I'm not too familiar with this kind of method either, at least not enough to propose to implement my own parallel implementation as of now.\r\n\r\nHowever I've found only one reference which reports an effective parallel implementation on unstructured grids:\r\n* M. F. Adams. A distributed memory unstructured Gauss-Seidel algorithm for\r\nmultigrid smoothers. In ACM/IEEE Proceedings of SC2001: High Performance\r\nNetworking and Computing, 2001.\r\n  http://dl.acm.org/citation.cfm?id=582038\r\n\r\nI found it mentioned in the following survey:\r\n* Edmond Chow, Robert D. Falgout, Jonathan J. Hu, Raymond S. Tuminaro, and Ulrike Meier Yang, A Survey of Parallelization Techniques for Multigrid Solvers, Frontiers of Parallel Processing for Scientific Computing, SIAM Publications, Philadelphia, PA, 2005.\r\n  http://www.edmondchow.com/pubs/parmg-survey-siam.pdf\r\n\r\n\r\nGiven the generic nature of `amgcl` I doubt it would be easy to add specialized versions of red-black Gauss-Siedel for regular grids, and we could say it's up to the user to implement it depending on the problem. All in all, I don't know if it's worth spending too much time on a parallel version for unstructured grids, where a polynomial smoother might have similar performance."}}