petsc-users Digest, Vol 2, Issue 33
Matthew Knepley
knepley at gmail.com
Tue Mar 3 08:15:15 CST 2009
On Tue, Mar 3, 2009 at 7:54 AM, STEPHANE TCHOUANMO <tchouanm at msn.com> wrote:
> Hi all,
>
> thank you Barry for the indication you gave me.
>
> As a matter of fact, i verified my jacobian and function evaluation again
> and again but i really dont see anything wrong in it.
> So i came back to the basic Laplacian problem (- \Delta u = f ) in the unit
> cube discretized in regular hexes. The numerical scheme i use is a
> vertex-centred finite volume scheme.
> The solution i get is correct compared to the exact solution (of second
> order) and i know my jacobian and residual evalutions are correct. But here
> is the log out i get.
>
>
> Event Count Time (sec)
> Flops/sec --- Global --- --- Stage --- Total
> Max Ratio Max Ratio Max Ratio Mess Avg len
> Reduct %T %F %M %L %R %T %F %M %L %R Mflop/s
>
> ------------------------------------------------------------------------------------------------------------------------
>
> --- Event Stage 0: Main Stage
>
> VecMDot 71 1.0 2.9587e-02 1.0 6.23e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 25 0 0 0 0 25 0 0 0 623
> VecNorm 77 1.0 3.3638e-02 1.0 4.24e+07 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 2 0 0 0 0 2 0 0 0 42
> VecScale 74 1.0 2.1052e-03 1.0 3.26e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 1 0 0 0 0 1 0 0 0 326
> VecCopy 80 1.0 3.4863e-03 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> VecSet 9 1.0 2.0776e-04 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> VecAXPY 5 1.0 2.3208e-04 1.0 3.99e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 399
> VecWAXPY 1 1.0 6.6995e-05 1.0 1.38e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 138
> VecMAXPY 74 1.0 3.8138e-02 1.0 5.18e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 27 0 0 0 0 27 0 0 0 518
> VecAssemblyBegin 4 1.0 9.8636e-06 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> VecAssemblyEnd 4 1.0 6.9494e-06 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> VecScatterBegin 3 1.0 3.0706e-04 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> VecNormalize 74 1.0 3.4648e-02 1.0 5.88e+07 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 3 0 0 0 0 3 0 0 0 59
> MatMult 73 1.0 1.4618e-01 1.0 2.22e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 45 0 0 0 0 45 0 0 0 222
> MatAssemblyBegin 2 1.0 6.9899e-06 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> MatAssemblyEnd 2 1.0 6.1999e-03 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> SNESSolve 1 1.0 6.7333e+01 1.0 1.08e+06 1.0 0.0e+00 0.0e+00
> 3.0e+00 99100 0 0100 99100 0 0100 1
> SNESLineSearch 1 1.0 5.1989e-01 1.0 8.91e+04 1.0 0.0e+00 0.0e+00
> 1.0e+00 1 0 0 0 33 1 0 0 0 33 0
> SNESFunctionEval 2 1.0 1.0441e+00 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 2.0e+00 2 0 0 0 67 2 0 0 0 67 0
> SNESJacobianEval 1 1.0 6.6026e+01 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 1.0e+00 97 0 0 0 33 97 0 0 0 33 0
> KSPGMRESOrthog 71 1.0 6.5884e-02 1.0 5.60e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0 51 0 0 0 0 51 0 0 0 560
> KSPSetup 1 1.0 2.2203e-04 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> KSPSolve 1 1.0 2.6036e-01 1.0 2.80e+08 1.0 0.0e+00 0.0e+00
> 0.0e+00 0100 0 0 0 0100 0 0 0 280
> PCSetUp 1 1.0 7.9495e-06 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
> PCApply 74 1.0 3.6445e-03 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 0 0 0 0 0 0 0 0 0 0 0
>
> ------------------------------------------------------------------------------------------------------------------------
>
> Memory usage is given in bytes:
>
> Object Type Creations Destructions Memory Descendants' Mem.
>
> --- Event Stage 0: Main Stage
>
> Index Set 3 3 111792 0
> Vec 44 3 223596 0
> Vec Scatter 3 3 0 0
> Matrix 1 0 0 0
> SNES 1 0 0 0
> Krylov Solver 1 0 0 0
> Preconditioner 1 0 0 0
> Viewer 2 0 0 0
> Draw 1 0 0 0
>
> ========================================================================================================================
> Average time to get PetscTime(): 1.60268e-06
>
>
> This shows that the Jacobian evaluation takes 97% of time and the residual
> just 2% in the SNESSolve. But if you look at the total MFlops, you can see
> that its null(i guess very low) for these phases. What seems to be long is
> the part in red concerning Vector manips. You can even see at the end that
> the most memory use is in Index set and Vec.
>
This analysis does not make sense. If you add all the time spent in the Vec
operations (in red), it is less than 1/100 of the time in the
SNES Solve. There is obviously a problem in that routine, if there is indeed
a problem. Do you have a model of the computation that
says that this time is too long?
Matt
--
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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