[petsc-dev] 3rd party GPU AMG solvers

[Mark Adams]

>
>
> it will nonetheless require a lot of convincing that at best they get
> moderate speed-ups, not the 580+x claimed in some of those early GPU
> papers...
>
>
Karli, we are talking about two different things. You are talking about
performance, and I applaud you for that, but I am talking about giving
customers what they want. They want to investigate GPUs. I will say that I
do not anticipate seeing any performance improvement.


>
> The fusion folks that I work with, and I assume other DOE offices, are
>> just looking at their codes, subroutine by subroutine, and having postdocs
>> look at GPUising them. We just need intelligent answers to their questions.
>> Even if we as sentient and passionate human being have opinions on the
>> approach that is implied by their questions, it is part of my job to just
>> give them a professional answer.
>>
>
> In the past ~18 months I've worked with applications that wanted to use
> GPUs in just that manner. Needless to say that you end up with touching
> almost everything to actually beat an existing (efficient) CPU-based
> application by less than a factor of 2. This involves MPI-parallel
> applications; it's much easier to get higher speedups if you don't need to
> communicate across ranks.
>
>
> I have enough now (thanks Jed and Lorena, et al!) to answer the AMGx
>> question sufficiently, and if you could give me a quick assessment of where
>> we are with hypre's GPU solver that would be great.
>>
>
> does "work in progress" suffice? ;-)
>

I will advertise it "as is" (this is a term of art in US law).

Thanks again,


>
> Best regards,
> Karli
>
>
>
>
>
>
>> On Thu, Jul 13, 2017 at 11:16 PM, Karl Rupp <rupp at iue.tuwien.ac.at
>> <mailto:rupp at iue.tuwien.ac.at>> wrote:
>>
>>     Hi Mark,
>>
>>         I hear Hypre has support for GPUs in a May release. Any word on
>>         the status of using it in PETSc?
>>
>>
>>     as far as I know, it is currently not supported in PETSc. I'll have
>>     a look at it and see what needs to be done to enable it.
>>
>>
>>         And we discussed interfacing to AMGx, which is complicated
>>         (precluded?) by not releasing source. Anything on the potential
>>         of interfacing to AMGx?  I think it would be great to make this
>>         available. It is on a lot of checkboxes. I would love to be able
>>         to say, yea you can use it.
>>
>>
>>     Lorena Barba's group actually interfaced PETSc to AMGx at some point
>>     (presented at GTC 2016 if I'm not mistaken). I'll reach out to them,
>>     maybe they have something to contribute.
>>
>>     Best regards,
>>     Karli
>>
>>
>>
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