{"action":"created","issue":{"url":"https://api.github.com/repos/flame/blis/issues/61","repository_url":"https://api.github.com/repos/flame/blis","labels_url":"https://api.github.com/repos/flame/blis/issues/61/labels{/name}","comments_url":"https://api.github.com/repos/flame/blis/issues/61/comments","events_url":"https://api.github.com/repos/flame/blis/issues/61/events","html_url":"https://github.com/flame/blis/issues/61","id":146421102,"number":61,"title":"Configuring maximum number of threads at runtime","user":{"login":"poulson","id":129293,"avatar_url":"https://avatars.githubusercontent.com/u/129293?v=3","gravatar_id":"","url":"https://api.github.com/users/poulson","html_url":"https://github.com/poulson","followers_url":"https://api.github.com/users/poulson/followers","following_url":"https://api.github.com/users/poulson/following{/other_user}","gists_url":"https://api.github.com/users/poulson/gists{/gist_id}","starred_url":"https://api.github.com/users/poulson/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/poulson/subscriptions","organizations_url":"https://api.github.com/users/poulson/orgs","repos_url":"https://api.github.com/users/poulson/repos","events_url":"https://api.github.com/users/poulson/events{/privacy}","received_events_url":"https://api.github.com/users/poulson/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":9,"created_at":"2016-04-06T20:16:07Z","updated_at":"2016-04-07T16:32:29Z","closed_at":null,"body":"A user of Elemental has been running into strange performance issues when building on top of BLIS that seem to be due to the environment variable `OMP_NUM_THREADS` being set to one still leading to a large performance degradation when the number of independent uses of BLIS times the number of configured threads is larger than the number of cores on the machine.\r\n\r\nWhile they have configured BLIS to use OpenMP with 16 threads, it is often preferred when using the library from within an MPI environment to be able to disable threading at runtime (or at least, decrease the number of threads).\r\n\r\nWhat environment variables should be set to one to have the same effect as exporting `OMP_NUM_THREADS=1` for other BLAS libraries? I would humbly suggest either adding support for `OMP_NUM_THREADS` or adding the full list of variables (including `BLIS_IR_NT`) to the wiki that need to be configured to have the same effect."},"comment":{"url":"https://api.github.com/repos/flame/blis/issues/comments/206982526","html_url":"https://github.com/flame/blis/issues/61#issuecomment-206982526","issue_url":"https://api.github.com/repos/flame/blis/issues/61","id":206982526,"user":{"login":"fgvanzee","id":5487570,"avatar_url":"https://avatars.githubusercontent.com/u/5487570?v=3","gravatar_id":"","url":"https://api.github.com/users/fgvanzee","html_url":"https://github.com/fgvanzee","followers_url":"https://api.github.com/users/fgvanzee/followers","following_url":"https://api.github.com/users/fgvanzee/following{/other_user}","gists_url":"https://api.github.com/users/fgvanzee/gists{/gist_id}","starred_url":"https://api.github.com/users/fgvanzee/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/fgvanzee/subscriptions","organizations_url":"https://api.github.com/users/fgvanzee/orgs","repos_url":"https://api.github.com/users/fgvanzee/repos","events_url":"https://api.github.com/users/fgvanzee/events{/privacy}","received_events_url":"https://api.github.com/users/fgvanzee/received_events","type":"User","site_admin":false},"created_at":"2016-04-07T16:32:29Z","updated_at":"2016-04-07T16:32:29Z","body":"@poulson: I think there is an NSF grant proposal in there: How to better specify and control parallelism in libraries, and communicate and parameterize parallelism back and forth between library and application (or library-caller).\r\n\r\nIn fact, I think we may have put it into our pending NSF grant. I'll have to check with Robert."}}