[petsc-users] Using PETSc with GPU

[Yuyun Yang]

Thanks Matt, I've seen that page, but there isn't that much documentation, and there is only one CUDA example, so I wanted to check if there may be more references or examples somewhere else. We have very large linear systems that need to be solved every time step, and which involves matrix-matrix multiplications, so we thought GPU could have some benefits, but we are unsure how difficult it is to migrate parts of the code to GPU with PETSc. From that webpage it seems like we only need to specify the Vec / Mat option on the command line and maybe change a few functions to have CUDA? The CUDA example however also involves using thrust and programming a kernel function, so I want to make sure I know how this works before trying to implement.

Thanks a lot,
Yuyun

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________________________________
From: Matthew Knepley <knepley at gmail.com>
Sent: Friday, March 15, 2019 2:54:02 PM
To: Yuyun Yang
Cc: petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Using PETSc with GPU

On Fri, Mar 15, 2019 at 5:30 PM Yuyun Yang via petsc-users <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>> wrote:
Hello team,

Our group is thinking of using GPUs for the linear solves in our code, which is written in PETSc. I was reading the 2013 book chapter on implementation of PETSc using GPUs but wonder if there is any more updated reference that I check out? I also saw one example cuda code online (using thrust), but would like to check with you if there is a more complete documentation of how the GPU implementation is done?

Have you seen this page? https://www.mcs.anl.gov/petsc/features/gpus.html

Also, before using GPUs, I would take some time to understand what you think the possible benefit can be.
For example, there is almost no benefit is you use BLAS1, and you would have a huge maintenance burden
with a different toolchain. This is also largely true for SpMV, since the bandwidth difference between CPUs
and GPUs is now not much. So you really should have some kind of flop intensive (BLAS3-like) work in there
somewhere or its hard to see your motivation.

  Thanks,

     Matt


Thanks very much!

Best regards,
Yuyun


--
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/>
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