QLogic OFED+ Host Software User Guide, Rev. B

B–Benchmark Programs
Benchmark 2: Measuring MPI Bandwidth Between Two Nodes
Benchmark 2: Measuring MPI Bandwidth
Between Two Nodes
The osu_bw benchmark measures the maximum rate that you can pump data
between two nodes. This benchmark also uses a ping-pong mechanism, similar to
the osu_latency code, except in this case, the originator of the messages
pumps a number of them (64 in the installed version) in succession using the
non-blocking MPI_I send function, while the receiving node consumes them as
quickly as it can using the non-blocking MPI_Irecv function, and then returns a
zero-length acknowledgement when all of the sent data has been received.
You can run this program by typing:
$ mpirun -H host1,host2 osu_bw
Typical output might look like:
# OSU MPI Bandwidth Test (Version 2.0)
# Size Bandwidth (MB/s)
1 3.549325
2 7.110873
4 14.253841
8 28.537989
16 42.613030
32 81.144290
64 177.331433
128 348.122982
256 643.742171
512 1055.355552
1024 1566.702234
2048 1807.872057
4096 1865.128035
8192 1891.649180
16384 1898.205188
32768 1888.039542
65536 1931.339589
131072 1942.417733
262144 1950.374843
524288 1954.286981
1048576 1956.301287
2097152 1957.351171
4194304 1957.810999
The increase in measured bandwidth with the messages’ size is because the
latency’s contribution to the measured time interval becomes relatively smaller.
D000046-005 B B-3