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

[Smith, Barry F.]

> On Aug 14, 2019, at 2:37 PM, Jed Brown <jed at jedbrown.org> wrote:
> 
> 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.

  And in single you get what?

> 
> 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.