Mark,
Yes, Jed has already asked for ways to select certain operations at runtime
that would get timed via the GPU timer. I am not sure of the ideal way to
handle it. One possibility is PetscLogGpuTimeEvent(event number) which
indicates events you want the time logged for. Another is
PetscLogGpuTimeObjectID(object ID) which indicates all events for a particular
object class would be logged. In either or both cases the PetscLogGPUTime()
calls would need to become smarter to determine when they are turned on and off
depending on the current state of the logging. Since the events are nested and
there can be multiple objects related to the timings I don't have a clear plan
in my mind.
Barry
> On May 16, 2022, at 7:31 PM, Mark Adams <[email protected]> wrote:
>
> I am not sure I understand the logic, we print the ratio of max/min.
> I report max and look at the ratio to see if I might be catching some load
> imbalance or whatever. Is there a problem with that workflow?
>
> I assume there is or you would not have done this, so can I add a method that
> I think also has legitimate values?
>
> I did observe a 15% hit on my whole stage with the GPU timers but I would
> still like to take my chances with:
>
> Landau Operator 29 1.0 1.1200e-02 1.0 4.54e+06 1.0 0.0e+00 0.0e+00
> 0.0e+00 3 0 0 0 0 40 4 0 0 0 405 509 0 0.00e+00 0
> 0.00e+00 100
> Landau Jacobian 15 1.0 7.8189e-03 1.0 4.54e+06 1.0 0.0e+00 0.0e+00
> 0.0e+00 2 0 0 0 0 28 4 0 0 0 580 731 0 0.00e+00 0
> 0.00e+00 100
> Landau Mass 14 1.0 3.3759e-03 1.0 0.00e+00 0.0 0.0e+00 0.0e+00
> 0.0e+00 1 0 0 0 0 12 0 0 0 0 0 0 0 0.00e+00 0
> 0.00e+00 0
>
> These methods require barriers at the end before they call MatSetValuesCOO,
> which is like < 1% of these total matrix times, so I trust the data w/o GPU
> times set.
>
> (The rest of the stage is the rest of the time step, which is mostly the
> linear solver, and I guess that is where the 15% comes from but I have not
> dug into it)
>
> Thanks,
> Mark
>
>
> On Wed, Apr 27, 2022 at 11:06 AM Barry Smith <[email protected]
> <mailto:[email protected]>> wrote:
>
> Only KSPSolve, SNESSolve, TSSolve will have legitimate values. "High-level"
> functions like PtAP can be asynchronous (meaning the GPU returns to the CPU
> to do more stuff) before they are complete, hence their timings would be
> incorrect and so they must be labeled with a special marker and not have
> numbers for time.
>
> Jed reports a possible 10% smaller time for KSPSolve() in this mode in some
> of his runs, compared to timing correctly the inner operations, and thus
> feels it is the best default.
>
> Barry
>
>
>> On Apr 27, 2022, at 10:08 AM, Mark Adams <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>>
>>
>> On Tue, Apr 26, 2022 at 8:00 PM Barry Smith <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> The current nan output has to be replaced to get the column alignment
>> correct, I just didn't feel like making that change also in the same MR.
>>
>> Something like Unknown or anything that fits in the column space would be
>> fine. It just means for the given run the timing numbers are not
>> meaningful/correct for those events.
>>
>> Just a note, just about every event is NAN for me. My GAMG setup that is all
>> CPU is NAN. High level functions like PtAP as well.
>> That said, adding -log_view_gpu_time is fine. Not worth the churn.
>>
>> This is to obtain the best meaningful results for the outer events per Jed
>> since timing the inner events accurately introduces extra time in the outer
>> events. That is it is not possible to have the best accurate times for both
>> inner events and outer events in the same run. So if you want to compare
>> KSPSolve timings, for example, you run as-is, it you want to examine,
>> low-level vector operations run also with -log_view_gpu_time but know that
>> the KSP times are higher than need be.
>>
>> Sorry for the confusion.
>>
>>
>>
>>
>>> On Apr 26, 2022, at 3:49 PM, Matthew Knepley <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> On Tue, Apr 26, 2022 at 12:03 PM Mark Adams <[email protected]
>>> <mailto:[email protected]>> wrote:
>>> Well, Nans are a clear sign that something is very wrong.
>>>
>>> Barry chose them so that it could not be mistaken for an actual number.
>>>
>>> Matt
>>>
>>> On Tue, Apr 26, 2022 at 11:52 AM Jacob Faibussowitsch <[email protected]
>>> <mailto:[email protected]>> wrote:
>>> There is an automatic warning that shows when you do run with
>>> `-log_view_gpu_time`, but perhaps there should also be an automatic warning
>>> when *not* running with it. It is unfortunate that NaN is the value printed
>>> as this implies a bug but AFAIK it is unavoidable (Barry can say more on
>>> this though).
>>>
>>> Best regards,
>>>
>>> Jacob Faibussowitsch
>>> (Jacob Fai - booss - oh - vitch)
>>>
>>> > On Apr 26, 2022, at 09:48, Jose E. Roman <[email protected]
>>> > <mailto:[email protected]>> wrote:
>>> >
>>> > You have to add -log_view_gpu_time
>>> > See https://gitlab.com/petsc/petsc/-/merge_requests/5056
>>> > <https://gitlab.com/petsc/petsc/-/merge_requests/5056>
>>> >
>>> > Jose
>>> >
>>> >
>>> >> El 26 abr 2022, a las 16:39, Mark Adams <[email protected]
>>> >> <mailto:[email protected]>> escribió:
>>> >>
>>> >> I'm seeing this on Perlmutter with Kokkos-CUDA. Nans in most log timing
>>> >> data except the two 'Solve' lines.
>>> >> Just cg/jacobi on snes/ex56.
>>> >>
>>> >> Any ideas?
>>> >>
>>> >> VecTDot 2 1.0 nan nan 1.20e+01 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 100
>>> >> VecNorm 2 1.0 nan nan 1.00e+01 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 100
>>> >> VecCopy 2 1.0 nan nan 0.00e+00 0.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 0
>>> >> VecSet 5 1.0 nan nan 0.00e+00 0.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 0
>>> >> VecAXPY 4 1.0 nan nan 2.40e+01 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 1 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 100
>>> >> VecPointwiseMult 1 1.0 nan nan 3.00e+00 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 100
>>> >> KSPSetUp 1 1.0 nan nan 0.00e+00 0.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 0 0 0 0 0 0 0 0 0 0 -nan -nan 0 0.00e+00
>>> >> 0 0.00e+00 0
>>> >> KSPSolve 1 1.0 4.0514e-04 1.0 5.50e+01 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 1 0 0 0 0 2 0 0 0 0 0 -nan 0 0.00e+00
>>> >> 0 0.00e+00 100
>>> >> SNESSolve 1 1.0 2.2128e-02 1.0 5.55e+05 1.0 0.0e+00 0.0e+00
>>> >> 0.0e+00 72 56 0 0 0 100100 0 0 0 25 -nan 0 0.00e+00
>>> >> 0 0.00e+00 0
>>> >
>>>
>>>
>>>
>>> --
>>> 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
>>>
>>> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
>>
>
