[petsc-users] Code speedup after upgrading

[Junchao Zhang]

In the new log, I saw

Summary of Stages:   ----- Time ------  ----- Flop ------  ---
Messages ---  -- Message Lengths --  -- Reductions --
                        Avg     %Total     Avg     %Total    Count
%Total     Avg         %Total    Count   %Total
 0:      Main Stage: 5.4095e+00   2.3%  4.3700e+03   0.0%  4.764e+05
3.0%  3.135e+02        1.0%  2.244e+04  12.6% 1: Solute_Assembly:
1.3977e+02  59.4%  7.3353e+09   4.6%  3.263e+06  20.7%  1.278e+03
 26.9%  1.059e+04   6.0%


But I didn't see any event in this stage had a cost close to 140s. What
happened?

 --- Event Stage 1: Solute_Assembly

BuildTwoSided       3531 1.0 2.8025e+0026.3 0.00e+00 0.0 3.6e+05
4.0e+00 3.5e+03  1  0  2  0  2   1  0 11  0 33     0
BuildTwoSidedF      3531 1.0 2.8678e+0013.2 0.00e+00 0.0 7.1e+05
3.6e+03 3.5e+03  1  0  5 17  2   1  0 22 62 33     0
VecScatterBegin     7062 1.0 7.1911e-02 1.9 0.00e+00 0.0 7.1e+05
3.5e+02 0.0e+00  0  0  5  2  0   0  0 22  6  0     0
VecScatterEnd       7062 1.0 2.1248e-01 3.0 1.60e+06 2.7 0.0e+00
0.0e+00 0.0e+00  0  0  0  0  0   0  0  0  0  0    73
SFBcastOpBegin      3531 1.0 2.6516e-02 2.4 0.00e+00 0.0 3.6e+05
3.5e+02 0.0e+00  0  0  2  1  0   0  0 11  3  0     0
SFBcastOpEnd        3531 1.0 9.5041e-02 4.7 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
SFReduceBegin       3531 1.0 3.8955e-02 2.1 0.00e+00 0.0 3.6e+05
3.5e+02 0.0e+00  0  0  2  1  0   0  0 11  3  0     0
SFReduceEnd         3531 1.0 1.3791e-01 3.9 1.60e+06 2.7 0.0e+00
0.0e+00 0.0e+00  0  0  0  0  0   0  0  0  0  0   112
SFPack              7062 1.0 6.5591e-03 2.5 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
SFUnpack            7062 1.0 7.4186e-03 2.1 1.60e+06 2.7 0.0e+00
0.0e+00 0.0e+00  0  0  0  0  0   0  0  0  0  0  2080
MatAssemblyBegin    3531 1.0 4.7846e+00 1.1 0.00e+00 0.0 7.1e+05
3.6e+03 3.5e+03  2  0  5 17  2   3  0 22 62 33     0
MatAssemblyEnd      3531 1.0 1.5468e+00 2.7 1.68e+07 2.7 0.0e+00
0.0e+00 0.0e+00  0  0  0  0  0   1  2  0  0  0   104
MatZeroEntries      3531 1.0 3.0998e-02 1.2 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


--Junchao Zhang



On Tue, Mar 23, 2021 at 5:24 PM Mohammad Gohardoust <gohardoust at gmail.com>
wrote:

> Thanks Dave for your reply.
>
> For sure PETSc is awesome :D
>
> Yes, in both cases petsc was configured with --with-debugging=0 and
> fortunately I do have the old and new -log-veiw outputs which I attached.
>
> Best,
> Mohammad
>
> On Tue, Mar 23, 2021 at 1:37 AM Dave May <dave.mayhem23 at gmail.com> wrote:
>
>> Nice to hear!
>> The answer is simple, PETSc is awesome :)
>>
>> Jokes aside, assuming both petsc builds were configured with
>> —with-debugging=0, I don’t think there is a definitive answer to your
>> question with the information you provided.
>>
>> It could be as simple as one specific implementation you use was improved
>> between petsc releases. Not being an Ubuntu expert, the change might be
>> associated with using a different compiler, and or a more efficient BLAS
>> implementation (non threaded vs threaded). However I doubt this is the
>> origin of your 2x performance increase.
>>
>> If you really want to understand where the performance improvement
>> originated from, you’d need to send to the email list the result of
>> -log_view from both the old and new versions, running the exact same
>> problem.
>>
>> From that info, we can see what implementations in PETSc are being used
>> and where the time reduction is occurring. Knowing that, it should be
>> clearer to provide an explanation for it.
>>
>>
>> Thanks,
>> Dave
>>
>>
>> On Tue 23. Mar 2021 at 06:24, Mohammad Gohardoust <gohardoust at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I am using a code which is based on petsc (and also parmetis). Recently
>>> I made the following changes and now the code is running about two times
>>> faster than before:
>>>
>>>    - Upgraded Ubuntu 18.04 to 20.04
>>>    - Upgraded petsc 3.13.4 to 3.14.5
>>>    - This time I installed parmetis and metis directly via petsc by
>>>    --download-parmetis --download-metis flags instead of installing them
>>>    separately and using --with-parmetis-include=... and
>>>    --with-parmetis-lib=... (the version of installed parmetis was 4.0.3 before)
>>>
>>> I was wondering what can possibly explain this speedup? Does anyone have
>>> any suggestions?
>>>
>>> Thanks,
>>> Mohammad
>>>
>>
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