[petsc-dev] Understanding -log_summary with GPUs

[Junchao Zhang]

Hi, Shri,
  I don't understand either. But there are many invocations of VecAXPY etc.
Is it possible some are done on CPU? Attach a debugger and set a breakpoint
on VecAXPY_SeqCUDA to see if it gets a hit. If yes, then see why.

--Junchao Zhang


On Tue, Mar 10, 2020 at 2:44 PM Abhyankar, Shrirang G via petsc-dev <
petsc-dev at mcs.anl.gov> wrote:

> Hello all,
>
>   I need help in understanding the output from -log_summary for the GPU
> related columns. I am currently simply setting -vec_type seqcuda which I
> believe performs the vector operations on the GPU. With -vec_type seqcuda,
> I presumed all vector operations are being done on the GPU. So, only the
> GPU MFlops will be logged, and CPU MFlops will be zero. But, -log_summary
> reports Mflops for both CPU and GPU. I do not understand why Mflops are
> shown both for CPU and GPU?
>
>
>
> What is the meaning of the last column – percent flops on the GPU? For
> instance, some operations such as VecDot show 100 %F, while others like
> VecAXPY have less. What is the meaning of this?
>
>
>
> Any other general comments on these numbers?
>
>
>
> Let me know if you need more information.
>
>
>
> Thanks,
>
> Shri
>
>
>
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