Re: Petsc slowness on a single processor machine‏

[Matthew Knepley]

2009/2/24 STEPHANE TCHOUANMO <tchouanm at msn.com>

>  Dear all,
>
> I use petsc to solve a nonlinear convection-diffusion type equation in
> porous media.
> The built linear system's size is 30000 and its resolution lasts about a
> hour on a single processor machine (my laptop...).
> I run for that a hundred time steps and have in average 4 Newton iterations
> per time step. So a hour seems huge to me with the optimized version of
> Petsc.
> I tryed to profile my code with the options "-log_summary" and "-info".
> What i get out of it is that the first time step lasts about 15min
> representing 25% of the total time and i think its not normal.
> The thing is, these 15min happen at the second call of the petsc routine
> "VecScatterCreate()" right after the first Newton residual.
>

We can't say anything without seeing the entire output of -log_summary.

   Matt


>
> Any idea?
> Thanks.
>
> Stephane
>
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-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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