[petsc-users] Understanding PETSc -log_summary

[Ajit Desai]

Thanks, Jed.
That is helpful.

*Ajit Desai*
 PhD Scholar, Carleton University, Canada

On Thu, Mar 16, 2017 at 8:00 AM, Jed Brown <jed at jedbrown.org> wrote:

> Ajit Desai <aero.aju at gmail.com> writes:
>
> > Hello Everyone,
> > A couple of questions on the *-log_summary* provided by PETSc.
>
> -log_view is the preferred name.
>
> > 1. *Avg-Flops & Avg-Flops/sec* are averaged among the participating cores
> > or averaged over the simulation time or both?
>
> Flops on each process is just the count (as logged by PetscLogFlops,
> which PETSc numerical functions call and you can too) over the time
> between PetscInitialize until the log is printed (usually
> PetscFinalize).  The time on each process is the wall clock time from
> PetscInitialize until the log is printed.  The Average, Max, Min, and
> total are over processes.
>
> > 2. *Max/Min Flops & Flops/sec* is an indication of load balancing?
> > In simulation-2 these ratios are high compared to simulation-1. Does that
> > mean simulation-2 is not well balanced?
>
> Yes, not balanced in terms of flops (correlated with time, but not a
> measure of time).  Look at the events to help see where.
>
> > Please follow the outputs from two different simulations
> > (Note: the problem size and the number of processors used are different).
> >
> > *Simulation-1*
> >                                    Max           Max/Min        Avg
> >    Total
> > Time (sec):            4.208e+02      1.00005   4.208e+02
> > Objects:                 7.100e+01      1.00000   7.100e+01
> > Flops:                     3.326e+11      1.31175   3.017e+11  4.826e+13
> > Flops/sec:              7.904e+08      1.31175   7.169e+08  1.147e+11
> > MPI Messages:      0.000e+00      0.00000   0.000e+00  0.000e+00
> >
> >
> > *SImulation-2:*
> >                                   Max          Max/Min        Avg
> > Total
> > Time (sec):           8.434e+02      1.00000   8.434e+02
> > Objects:                7.300e+01      1.02817   7.102e+01
> > Flops:                   6.555e+11      1.85115   5.798e+11  3.711e+14
> > Flops/sec:            7.772e+08      1.85115   6.874e+08  4.400e+11
> > MPI Messages:    0.000e+00      0.00000   0.000e+00  0.000e+00
> >
> > We're trying to understand the performance of our solver using these
> > outputs.
> > Any comments in relation to that will be helpful.
> >
> > Thanks & Regards,
> > *Ajit Desai*
> >  PhD Scholar, Carleton University, Canada
>
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