User guide

A–Benchmark Programs
Benchmark 3: Messaging Rate Microbenchmarks
A-10 IB0054606-02 A
Note the improved message rate at small message sizes of ~25 million compared
to the rate of 22.8 million measured with osu_mbw_mr. Also note that it only takes
a message of size 121 bytes to generate half of the peak uni-directional
bandwidth.
The following is an example output when running with the bidirectional option
(-b):
$ mpirun -H host1,host2 -np 24 \
/usr/mpi/gcc/openmpi-1.4.3-qlc/tests/qlogic/mpi_multibw -b
# PathScale Modified OSU MPI Bandwidth Test
(OSU Version 2.2, PathScale $Revision: 1.1.2.1 $)
# Running on 12 procs per node (bi-directional traffic for
each process pair)
# Size Aggregate Bandwidth (MB/s) Messages/s
1 34.572819 34572819.324348
2 68.984920 34492459.942272
4 137.870850 34467712.532016
8 274.914966 34364370.730843
16 438.182185 27386386.585309
32 871.077525 27221172.671073
64 1743.576039 27243375.616870
128 3046.774606 23802926.607917
256 3968.178042 15500695.477711
512 4558.456908 8903236.148204
1024 4876.777738 4762478.259397
2048 5050.255245 2465944.943769
4096 5063.142612 1236118.801851
8192 5234.475557 638974.066993
16384 6255.483598 381804.418801
32768 6236.354159 190318.425252
65536 6288.370045 95952.912066
131072 6330.494823 48297.842586
262144 6351.690777 24229.777437
524288 6353.021307 12117.426504
1048576 6353.890433 6059.542115
2097152 6353.951840 3029.800339
4194304 6354.671923 1515.071851
Searching for N/2 bandwidth. Maximum Bandwidth of 6354.671923
MB/s...
Found N/2 bandwidth of 3184.322181 MB/s at size 170 bytes