[petsc-dev] [petsc-maint] running CUDA on SUMMIT

[Jed Brown]

Mark Adams via petsc-dev <petsc-dev at mcs.anl.gov> writes:

> On Wed, Aug 14, 2019 at 2:35 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
>
>>
>>   Mark,
>>
>>    Would you be able to make one run using single precision? Just single
>> everywhere since that is all we support currently?
>>
>>
> Experience in engineering at least is single does not work for FE
> elasticity. I have tried it many years ago and have heard this from others.
> This problem is pretty simple other than using Q2. I suppose I could try
> it, but just be aware the FE people might say that single sucks.

When they say that single sucks, is it for the definition of the
operator or the preconditioner?

As point of reference, we can apply Q2 elasticity operators in double
precision at nearly a billion dofs/second per GPU.

I'm skeptical of big wins in preconditioning (especially setup) due to
the cost and irregularity of indexing being large compared to the
bandwidth cost of the floating point values.