[petsc-users] Interpreting flamegraph and profiling logs

[Alfredo J Duarte Gomez]

Good afternoon PETSC team,

I am doing some profiling on one of my applications (petsc 3.15) using the
command options:
 -log_view :performance.out
-log_view :flame.out:ascii_flamegraph.

I want to understand the specifics of the gnereated flamegraphs and I am
attaching performance.out and flame.out to this email.

I am assuming that the flamegraphs represent what is labeled "MPI Messages"
in the regular output file (i.e. performance.out) instead of time or is it
some other quantity? Since the "unit" of these flamegraphs is not time when
I load into speedscope app and quantities most closely resemble the order
of magnitude of the messages sent.

My application being an unsteady solver, I can understand that in time
percentage, the amount of time spent in SNESsolve is almost equal to the
amount spent in TSStep (~1.63e02 s, see performance.out). However, that
percentage is not represented in the flamegraph (97% vs 82% in flame.out).
How would I interpret this difference in percentage?

Thanks,

Alfredo
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