[petsc-users] Poor speed up for KSP example 45

[Amin Sadeghi]

Hi,

I ran KSP example 45 on a single node with 32 cores and 125GB memory using
1, 16 and 32 MPI processes. Here's a comparison of the time spent during
KSP.solve:

- 1 MPI process: ~98 sec, speedup: 1X
- 16 MPI processes: ~12 sec, speedup: ~8X
- 32 MPI processes: ~11 sec, speedup: ~9X

Since the problem size is large enough (8M unknowns), I expected a speedup
much closer to 32X, rather than 9X. Is this expected? If yes, how can it be
improved?

I've attached three log files for more details.

Sincerely,
Amin
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