[petsc-users] Petsc Performance Help

[Jed Brown]

On Fri, Mar 16, 2012 at 14:52, <Nan.Jia at dartmouth.edu> wrote:

> Dear PETSc Group,
> I am tuning the efficiency of my PETSc code for a while, but get very
> little progress. So can anyone help me to analysis the log? Any suggestions
> will be appreciated.
>
> My problem is time dependent. At every time step, two about 6000 by 6000
> sparse matrices need to be solved, which come from a Poisson equation. I
> use both sequential and parallel AIJ format to store matrices, but the
> performances are both not very good.
>

1. You need to heed the huge warning

      ##########################################################
      #                                                        #
      #                          WARNING!!!                    #
      #                                                        #
      #   This code was compiled with a debugging option,      #
      #   To get timing results run config/configure.py        #
      #   using --with-debugging=no, the performance will      #
      #   be generally two or three times faster.              #
      #                                                        #
      ##########################################################



2. You only spend 18 of 880 seconds in the solver. What do you want?

3. The problem is too small to get significant parallel speedup.

http://www.mcs.anl.gov/petsc/documentation/faq.html#slowerparallel
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