$ cat /etc/hosts 
127.0.0.1       localhost
::1             localhost
172.31.1.1      mic0
172.31.2.1      mic1

$ mpirun -host localhost -n 1 ./mpitest : -host mic0 -n 1 ~/mpitest.knl : -host mic1 -n 1 ~/mpitest.knl
Hello world: rank 0 of 3 running on knl-lb0
Hello world: rank 1 of 3 running on mic0
Hello world: rank 2 of 3 running on mic1
FROM RANK 0 - numthreads = 64
FROM RANK 2 - numthreads = 272
FROM RANK 1 - numthreads = 272
Elapsed time from rank 0:   12114.05 (usec)
Elapsed time from rank 1:  136089.09 (usec)
Elapsed time from rank 2:  125049.11 (usec)
rank 0 pi=   3.141597270966