{"action":"opened","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":0,"created_at":"2016-04-06T20:16:07Z","updated_at":"2016-04-06T20:16:07Z","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` having no effect on the maximum number of threads used by BLIS (it would appear that `BLIS_IR_NT` and friends should be used).\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."}}