[petsc-users] PetscLogEvent

[Gu Shiyuan]

Hi all,
    I make up a learning examples but cannot explain the result:
    In the following codes, everything inside the stage[1] is between
PetscLogEventBegin() and PetscLogEventEnd(), so I expect the time of the
EVENT_MGSolver should take up 100% percent of the time in this stage. But
log_summary only gives me 97%. Where is the 3%?

    PetscLogStagePush(stages[1]);
    PetscLogEventBegin(MGSolver,0,0,0,0);
       for(l=0;l<100;l++){
           ///// some functions calls
     }
     PetscLogEventEnd(MGSolver,0,0,0,0);
     PetscLogStagePop();

-log_summary:
--- Event Stage 2:

MatMult           241600 1.0 3.4837e+01 1.0 1.06e+10 1.0 0.0e+00 0.0e+00
0.0e+00 64 75  0  0  0  65 75  0  0  0   303
MatMultAdd         53200 1.0 2.9537e+00 1.0 6.91e+08 1.0 0.0e+00 0.0e+00
0.0e+00  5  5  0  0  0   6  5  0  0  0   234
MatSolve           35200 1.0 6.0787e-02 1.0 3.01e+06 1.0 0.0e+00 0.0e+00
0.0e+00  0  0  0  0  0   0  0  0  0  0    50
VecDot            272000 1.0 1.6983e+00 1.0 7.64e+08 1.0 0.0e+00 0.0e+00
0.0e+00  3  5  0  0  0   3  5  0  0  0   450
VecNorm            35200 1.0 4.8882e-02 1.0 5.28e+05 1.0 0.0e+00 0.0e+00
0.0e+00  0  0  0  0  0   0  0  0  0  0    11
VecScale          117600 1.0 6.2790e-01 1.0 2.62e+08 1.0 0.0e+00 0.0e+00
0.0e+00  1  2  0  0  0   1  2  0  0  0   417
VecCopy           141600 1.0 1.4639e+00 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
0.0e+00  3  0  0  0  0   3  0  0  0  0     0
VecSet             35200 1.0 3.4475e-02 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            35200 1.0 3.4980e-02 1.0 5.63e+05 1.0 0.0e+00 0.0e+00
0.0e+00  0  0  0  0  0   0  0  0  0  0    16
VecAYPX           288400 1.0 3.4488e+00 1.0 8.93e+08 1.0 0.0e+00 0.0e+00
0.0e+00  6  6  0  0  0   6  6  0  0  0   259
VecWAXPY          100800 1.0 1.3907e+00 1.0 3.81e+08 1.0 0.0e+00 0.0e+00
0.0e+00  3  3  0  0  0   3  3  0  0  0   274
VecPointwiseMult  320000 1.0 4.8273e+00 1.0 5.72e+08 1.0 0.0e+00 0.0e+00
0.0e+00  9  4  0  0  0   9  4  0  0  0   119
KSPSolve           17600 1.0 5.6411e-01 1.0 6.14e+06 1.0 0.0e+00 0.0e+00
0.0e+00  1  0  0  0  0   1  0  0  0  0    11
PCApply            35200 1.0 1.2111e-01 1.0 3.01e+06 1.0 0.0e+00 0.0e+00
0.0e+00  0  0  0  0  0   0  0  0  0  0    25
MGSolver               1 1.0 5.3215e+01 1.0 1.41e+10 1.0 0.0e+00 0.0e+00
0.0e+00 97100  0  0  0 100100  0  0  0   265
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Moreover,
What are the last four parameters of  PetscLogEventBegin() used for? The
manually vaguely states that "objects associated with the event".
The provided examples set them to zeros. In what situation should we pass a
non-zero?
 I can obtain profiling information with -log_summary but I get nothing with
-log or -log_all. Did I miss any steps for -log/-log_all to work?
Thanks.
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