QLogic OFED+ Host Software User Guide, Rev. B

B–Benchmark Programs
Benchmark 4: Measuring MPI Latency in Host Rings
Searching for N/2 bandwidth. Maximum Bandwidth of 1958.400649
MB/s...
Found N/2 bandwidth of 992.943275 MB/s at size 153 bytes
Benchmark 4: Measuring MPI Latency in Host
Rings
The program mpi_latency measures latency in a ring of hosts. Its syntax is
different from Benchmark 1 in that it takes command line arguments that let you
specify the message size and the number of messages to average the results. For
example, running on the nodes, host1, host2, host3 and host4, the command:
$ mpirun -np 4 -H host[1-4] mpi_latency 100 0
Might produce output like this:
0 1.760125
This output indicates that it took an average of 1.76 microseconds per hop to send
a zero-length message from the first host, to the second, to the third, to the fourth,
and then receive replies back in the other direction.
D000046-005 B B-5