[mpich-discuss] Question about mpich bandwidth vs message-size plot

[Sajid Ali]

Hi MPICH-developers,

I’ve been trying to benchmark mpi software currently available on my univ.
cluster with OSU micro benchmarks. I used this script to build and run the
benchmark :
https://github.com/s-sajid-ali/nu-quest-mpi/blob/master/curr_mpi_bench/submit.sh

And here is a plot of the results I obtained :
[image: curr_mpi.png]

Could someone give me a clue as to why the behaviour of mpich bandwidth vs
latency is so odd ? Why does the bandwidth increase first and then fall off
at high message sizes?

I’m also attaching the config.log for this particular mpich build which
seems to indicate that MPICH was built with ch3 and nemesis:tcp. Does this
mean that it didn’t pick up the infiniband libraries or that it is somehow
using IPoIB? Is there a way to get this information ?

Thanks in advance for the help!


--
Sajid Ali | PhD Candidate
Applied Physics
Northwestern University
s-sajid-ali.github.io
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