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.
it is fine to say that "here is what you can try, but don't expect
performance gains". My experience is, however, that people then go
ahead, try it, *and* expect performance gains (of course for
inappropriate system sizes, etc.). Since they invested time in exploring
GPUs, there is an implicit expectation that there must be a ROI...
Best regards,
Karli
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
<[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
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
