/usr/lib64/openmpi/bin/mpirun --machinefile mpi_hosts --bynode -np 16 /path/to/IOR -F -u -t 1m -b 16g -i 1 -o /my/file/system/out_file

#0  0x00007f3ac49e95fe in mlx4_poll_cq () from /usr/lib64/libmlx4-m-rdmav2.so
#1  0x00007f3ac6ce0918 in ?? () from /usr/lib64/openmpi/lib/openmpi/mca_btl_openib.so
#2  0x000000385a6f0d5a in opal_progress () from /usr/lib64/openmpi/lib/libmpi.so.1
#3  0x00007f3ac7511e05 in ?? () from /usr/lib64/openmpi/lib/openmpi/mca_pml_ob1.so
#4  0x000000385a666cac in PMPI_Recv () from /usr/lib64/openmpi/lib/libmpi.so.1
#5  0x0000000000404bd7 in CountTasksPerNode (numTasks=16, comm=0x628a80) at IOR.c:526
#6  0x0000000000407d53 in SetupTests (argc=11, argv=0x7fffe61fa2a8) at IOR.c:1402
#7  0x0000000000402e96 in main (argc=11, argv=0x7fffe61fa2a8) at IOR.c:134

MPI_Recv(hostname, MAX_STR, MPI_CHAR, MPI_ANY_SOURCE, MPI_ANY_TAG, comm, &status);