I am using mpich3 3.0.4 built with Intel 13.0 compilers on Centos 6.5. I am trying to use the 'bind-to core' and 'map-by core:2' options to mpiexec. I am able to run this successfully on nodes in my cluster where there are 2 sockets. However, when I try to run it on a 4 socket node with 12 cores per socket, I get the following errors: [proxy:0:0@f02] get_nbobjs_by_type (./tools/topo/hwloc/topo_hwloc.c:189): assert (nb % x == 0) failed [proxy:0:0@f02] handle_bitmap_binding (./tools/topo/hwloc/topo_hwloc.c:450): unable to get number of objects [proxy:0:0@f02] HYDT_topo_hwloc_init (./tools/topo/hwloc/topo_hwloc.c:527): error binding with bind "core" and map "core:2" [proxy:0:0@f02] HYDT_topo_init (./tools/topo/topo.c:60): unable to initialize hwloc [proxy:0:0@f02] launch_procs (./pm/pmiserv/pmip_cb.c:520): unable to initialize process topology [proxy:0:0@f02] HYD_pmcd_pmip_control_cmd_cb (./pm/pmiserv/pmip_cb.c:893): launch_procs returned error [proxy:0:0@f02] HYDT_dmxu_poll_wait_for_event (./tools/demux/demux_poll.c:77): callback returned error status [proxy:0:0@f02] main (./pm/pmiserv/pmip.c:206): demux engine error waiting for event [mpiexec@f02] control_cb (./pm/pmiserv/pmiserv_cb.c:202): assert (!closed) failed [mpiexec@f02] HYDT_dmxu_poll_wait_for_event (./tools/demux/demux_poll.c:77): callback returned error status [mpiexec@f02] HYD_pmci_wait_for_completion (./pm/pmiserv/pmiserv_pmci.c:197): error waiting for event [mpiexec@f02] main (./ui/mpich/mpiexec.c:331): process manager error waiting for completion Any idea what could be causing this problem? Susan Schwarz Research Computing Dartmouth