Note the following still indicates that "--bind-to none" is the default:
-bash-4.2$ mpirun --help | grep -A2 'bind-to ' --bind-to <arg0> Policy for binding processes [none (default) | hwthread | core | socket | numa | board] (supported qualifiers: overload-allowed,if-supported) However, Jeff has clearly stated ( http://www.open-mpi.org/community/lists/devel/2013/12/13456.php) that bind-to-core is to be the default in 1.7.4. The --map-by and --rank-by outputs are similarly out-dated: -bash-4.2$ mpirun --help | grep -A1 'map-by ' --map-by <arg0> Mapping Policy [slot (default) | hwthread | core | socket | numa | board | node] -bash-4.2$ mpirun --help | grep -A1 'rank-by ' --rank-by <arg0> Ranking Policy [slot (default) | hwthread | core | socket | numa | board | node] -Paul -- Paul H. Hargrove phhargr...@lbl.gov Future Technologies Group Computer and Data Sciences Department Tel: +1-510-495-2352 Lawrence Berkeley National Laboratory Fax: +1-510-486-6900