[petsc-users] CPU vs GPU for PETSc applications

[Matthew Knepley]

On Thu, Mar 10, 2016 at 12:29 PM, Justin Chang <jychang48 at gmail.com> wrote:

> Hi all,
>
> When would I ever use GPU computing for a finite element simulation where
> the limiting factor of performance is the memory bandwidth bound? Say I
> want to run problems similar to SNES ex12 and 62. I understand that there
> is an additional bandwidth associated with offloading data from the CPU to
> GPU but is there more to it? I recall reading through some email threads
> about GPU's potentially giving you a speed up of 3x that on a CPU but the
> gain in performance may not be worth the increase in time moving data
> around.


The main use case is if you are being forced to use a machine which has
GPUs. Then you can indeed get some benefit
from the larger bandwidth. You need a problem where you are doing a bunch
of iterations to make sending the initial data
down worth it.

It would certainly be better if you are computing the action of your
operator directly on the GPU, but that is much more
disruptive to the code right now.

  Matt


> Thanks,
> Justin
>
-- 
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
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