{"action":"opened","issue":{"url":"https://api.github.com/repos/espressopp/espressopp/issues/128","repository_url":"https://api.github.com/repos/espressopp/espressopp","labels_url":"https://api.github.com/repos/espressopp/espressopp/issues/128/labels{/name}","comments_url":"https://api.github.com/repos/espressopp/espressopp/issues/128/comments","events_url":"https://api.github.com/repos/espressopp/espressopp/issues/128/events","html_url":"https://github.com/espressopp/espressopp/issues/128","id":184872550,"number":128,"title":"Number of idle/sleeping threads?","user":{"login":"fedepad","id":1518419,"avatar_url":"https://avatars.githubusercontent.com/u/1518419?v=3","gravatar_id":"","url":"https://api.github.com/users/fedepad","html_url":"https://github.com/fedepad","followers_url":"https://api.github.com/users/fedepad/followers","following_url":"https://api.github.com/users/fedepad/following{/other_user}","gists_url":"https://api.github.com/users/fedepad/gists{/gist_id}","starred_url":"https://api.github.com/users/fedepad/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/fedepad/subscriptions","organizations_url":"https://api.github.com/users/fedepad/orgs","repos_url":"https://api.github.com/users/fedepad/repos","events_url":"https://api.github.com/users/fedepad/events{/privacy}","received_events_url":"https://api.github.com/users/fedepad/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/espressopp/espressopp/labels/question","name":"question","color":"cc317c"}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2016-10-24T15:22:51Z","updated_at":"2016-10-24T15:22:51Z","closed_at":null,"body":"Hi,\r\na general question.\r\n\r\nToday I was running some single-node experiments (here a node has 64 cores).\r\nI called the examples/polymer_melt/polymer_melt.py script via:\r\n\r\nmpirun -np 64 python polymer_melt.py\r\n\r\nwhere the replica factors were set to xdim=ydim=zdim=5, which \"generates\" 5M particles.\r\n\r\nLooking at the report from the job scheduler I noticed a high number of threads were generated:\r\n\r\nResource usage summary:\r\n.........\r\n Max Threads :  4102\r\n ........\r\n\r\nMonitoring the job showed the same using the \"ps\" command.\r\nIt looks like 64 threads are created per MPI rank; one is running and doing work while the others are sleeping and seem to do nothing at the moments I sampled.\r\n\r\nI then tried to change the number of cores used to see how things were changing.\r\nRunning with 24 cores for example showed a number of threads for python polymer_melt.py that is 24 x 64, i.e. 64 threads per MPI rank, again only one per MPI rank doing the work and the other sleeping.\r\n\r\nIs this a know fact? Has this been seen by someone else before or I'm the only one seeing this. Just this question I had since I never looked into that before.\r\nAlthough it's not a problem, I was a little bit surprised by the high number and why 64.\r\n\r\nAttached the brief sample from \"ps\" on the node running the program.\r\n[psoutfile2.txt](https://github.com/espressopp/espressopp/files/548247/psoutfile2.txt)\r\n"}}
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