[petsc-users] MatCreateSeqAIJWithArrays for GPU / cusparse

[Junchao Zhang]

On Thu, Jan 5, 2023 at 10:32 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>
> > On Jan 5, 2023, at 3:42 PM, Jed Brown <jed at jedbrown.org> wrote:
> >
> > Mark Adams <mfadams at lbl.gov> writes:
> >
> >> Support of HIP and CUDA hardware together would be crazy,
> >
> > I don't think it's remotely crazy. libCEED supports both together and
> it's very convenient when testing on a development machine that has one of
> each brand GPU and simplifies binary distribution for us and every package
> that uses us. Every day I wish PETSc could build with both simultaneously,
> but everyone tells me it's silly.
>
>   Not everyone at all; just a subset of everyone. Junchao is really the
> hold-out :-)
>
I am not, instead I think we should try (I fully agree it can ease binary
distribution).  But satish needs to install such a machine first :)
There are issues out of our control if we want to mix GPUs in execution.
For example, how to do VexAXPY on a cuda vector and a hip vector? Shall we
do it on the host? Also, there are no gpu-aware MPI implementations
supporting messages between cuda memory and hip memory.

>
>   I just don't care about "binary packages" :-); I think they are an
> archaic and bad way of thinking about code distribution (but yes the
> alternatives need lots of work to make them flawless, but I think that is
> where the work should go in the packaging world.)
>
>    I go further and think one should be able to automatically use a CUDA
> vector on a HIP device as well, it is not hard in theory but requires
> thinking about how we handle classes and subclasses a little to make it
> straightforward; or perhaps Jacob has fixed that also?
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