{"action":"created","issue":{"url":"https://api.github.com/repos/libMesh/libmesh/issues/1058","repository_url":"https://api.github.com/repos/libMesh/libmesh","labels_url":"https://api.github.com/repos/libMesh/libmesh/issues/1058/labels{/name}","comments_url":"https://api.github.com/repos/libMesh/libmesh/issues/1058/comments","events_url":"https://api.github.com/repos/libMesh/libmesh/issues/1058/events","html_url":"https://github.com/libMesh/libmesh/issues/1058","id":170020406,"number":1058,"title":"MPI_Scatter in parallel.h?","user":{"login":"permcody","id":3036960,"avatar_url":"https://avatars.githubusercontent.com/u/3036960?v=3","gravatar_id":"","url":"https://api.github.com/users/permcody","html_url":"https://github.com/permcody","followers_url":"https://api.github.com/users/permcody/followers","following_url":"https://api.github.com/users/permcody/following{/other_user}","gists_url":"https://api.github.com/users/permcody/gists{/gist_id}","starred_url":"https://api.github.com/users/permcody/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/permcody/subscriptions","organizations_url":"https://api.github.com/users/permcody/orgs","repos_url":"https://api.github.com/users/permcody/repos","events_url":"https://api.github.com/users/permcody/events{/privacy}","received_events_url":"https://api.github.com/users/permcody/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":7,"created_at":"2016-08-08T20:42:09Z","updated_at":"2016-08-19T21:42:13Z","closed_at":"2016-08-15T16:14:31Z","body":"In doing some preliminary runs of the optimized grain tracker I made crude observations of the memory usage and am simply blown away by how much my data structures appear to occupy. Running 6000 grains on 180^3 mesh seemed to increase the memory usage right after the `allgather` operation (cause of the non-issue in #1039) by over a GB per processor! This is the optimized version mind you!  The back of the envelope calculations don't seem to add up to this amount of memory but I do have a lot of data in sets which takes often more than 4x the amount of memory for POD types AND that data structure exists on every processor, so maybe...\r\n\r\nI'm thinking about really digging into this algorithm and changing it so that only the root process maintains the big data structure and the remaining ranks maintain only local data and local to global mappings. I don't think this will be too difficult but I could really use `MPI_Scatter` to get this done. Can we add this to parallel.h?\r\n\r\nTL;DR;\r\nI'd love to have MPI_Scatter in parallel.h. Any objections?\r\n"},"comment":{"url":"https://api.github.com/repos/libMesh/libmesh/issues/comments/241142838","html_url":"https://github.com/libMesh/libmesh/issues/1058#issuecomment-241142838","issue_url":"https://api.github.com/repos/libMesh/libmesh/issues/1058","id":241142838,"user":{"login":"roystgnr","id":2367346,"avatar_url":"https://avatars.githubusercontent.com/u/2367346?v=3","gravatar_id":"","url":"https://api.github.com/users/roystgnr","html_url":"https://github.com/roystgnr","followers_url":"https://api.github.com/users/roystgnr/followers","following_url":"https://api.github.com/users/roystgnr/following{/other_user}","gists_url":"https://api.github.com/users/roystgnr/gists{/gist_id}","starred_url":"https://api.github.com/users/roystgnr/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/roystgnr/subscriptions","organizations_url":"https://api.github.com/users/roystgnr/orgs","repos_url":"https://api.github.com/users/roystgnr/repos","events_url":"https://api.github.com/users/roystgnr/events{/privacy}","received_events_url":"https://api.github.com/users/roystgnr/received_events","type":"User","site_admin":false},"created_at":"2016-08-19T21:42:13Z","updated_at":"2016-08-19T21:42:13Z","body":"I really like that, yeah."}}
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