[petsc-users] MatCreateSeqAIJWithArrays for GPU / cusparse

[Barry Smith]

  So Jed's "everyone" now consists of "no one" and Jed can stop complaining that "everyone" thinks it is a bad idea.



> On Jan 5, 2023, at 11:50 PM, Junchao Zhang <junchao.zhang at gmail.com> wrote:
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> On Thu, Jan 5, 2023 at 10:32 PM Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>> wrote:
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>> > On Jan 5, 2023, at 3:42 PM, Jed Brown <jed at jedbrown.org <mailto:jed at jedbrown.org>> wrote:
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>> > Mark Adams <mfadams at lbl.gov <mailto:mfadams at lbl.gov>> writes:
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>> >> 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.
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>>   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.)
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>>    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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