[petsc-users] log_summary time ratio and flops ratio

[Jed Brown]

Matthew Knepley <knepley at gmail.com> writes:
>> I attached the full summary. At the end, it has
>>
>> Average time to get PetscTime(): 0
>> Average time for MPI_Barrier(): 8.3971e-05
>> Average time for zero size MPI_Send(): 7.16746e-06
>>
>> Is it an indication of slow network?
>>
>
> I think so. It takes nearly 100 microseconds to synchronize processes.

Edison with 65536 processes:
Average time for MPI_Barrier(): 4.23908e-05
Average time for zero size MPI_Send(): 2.46466e-06

Mira with 16384 processes:
Average time for MPI_Barrier(): 5.7075e-06
Average time for zero size MPI_Send(): 1.33179e-05

Titan with 131072 processes:
Average time for MPI_Barrier(): 0.000368595
Average time for zero size MPI_Send(): 1.71567e-05
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