Bruno

I hear from the AMReX developers that others have run AMReX-based
codes on the GPUs on Marconi. So all is good.

-erik

On Fri, Jul 10, 2020 at 11:56 AM Bruno Giacomazzo
<[email protected]> wrote:
>
> Erik,
>   thanks a lot for the information and for the work you are doing. I will 
> contact CINECA and ask about AMReX support.
>
> Cheers,
> Bruno
>
>
> Il giorno ven 10 lug 2020 alle ore 17:53 Erik Schnetter 
> <[email protected]> ha scritto:
>>
>> Bruno
>>
>> We are looking into GPU support in the context of the CarpetX project.
>> CarpetX <https://bitbucket.org/eschnett/cactusamrex/src/master/> is a
>> new driver, currently being developed, that uses AMReX
>> <https://amrex-codes.github.io/amrex/> as back-end to provide the
>> lower-level AMR capabilities. AMReX supports GPUs, and we intend to
>> ensure that CarpetX (and thus the Einstein Toolkit) supports GPUs from
>> the beginning. I am (personally) currently not using the larger EU HPC
>> systems, but we have Summit <https://www.olcf.ornl.gov/summit/> in the
>> North American region, and Summit requires highly efficient GPU codes
>> as well.
>>
>> Having said this, CarpetX is still in the very early stages, so I can
>> only present a plan and not yet a solution. We know that AMReX
>> supports GPUs, and AMReX is funded and actively developed, so we have
>> a very well engineered foundation, but exactly how to expose this to
>> Cactus and the Einstein Toolkit isn't quite clear yet. My hope
>> (dream?) is that it will be possible to write somewhat generic C++
>> code that will run unchanged on both CPUs and GPUs, and that making
>> this work efficiently will work without having to maintain two
>> different codes. Whether this is possible will remain to be seen.
>> Maybe we need to go towards automated code generation (generating both
>> CPU and GPU codes from the same script) to make this happen.
>>
>> I don't see AMReX on the list of supported software for Marconi. Do
>> you want to investigate? I wonder whether this is due to lack of
>> interest from users, or whether they looked into AMReX and there was a
>> roadblock. (I would not assume so, but you never know.)
>>
>> -erik
>>
>> On Fri, Jul 10, 2020 at 11:11 AM Bruno Giacomazzo
>> <[email protected]> wrote:
>> >
>> > Dear All,
>> >   I would like to know if there is any plan to port the Einstein Toolkit 
>> > to GPUs. This is something that we may also discuss at the next Einstein 
>> > Toolkit workshop if there is time.
>> >
>> >   The reason I'm asking is that in Italy, CINECA (part of the EU HPC 
>> > consortium) just bought its new HPC cluster and it is completely GPU based 
>> > (Marconi100, https://www.hpc.cineca.it/hardware/marconi100, currently 
>> > ranked in the top 10 of the fastest supercomputers in the world).
>> >
>> >    Speaking with people at CINECA, I was informed that HPC-Europe is 
>> > moving to GPU and, while cpu codes will be still supported for the next 5 
>> > years (with some of the new clusters still having a limited number of 
>> > nodes for cpu codes), the plan is to move to 100% GPU clusters at the EU 
>> > level. I was indeed told that the latest 3 HPC clusters bought by 
>> > HPC-Europe are GPU clusters. The next Italian HPC machine will also be a 
>> > GPU cluster, with a limited number of cpu nodes (they estimate ~3500 nodes 
>> > with GPUs and ~1000 nodes with cpus).
>> >
>> > Thanks,
>> > Bruno
>> >
>> > --
>> >
>> > Prof. Bruno Giacomazzo
>> > Department of Physics
>> > University of Milano-Bicocca
>> > Piazza della Scienza 3
>> > 20126 Milano
>> > Italy
>> >
>> > email: [email protected]
>> > phone: (+39) 02 6448 2321
>> > web: http://www.brunogiacomazzo.org
>> >
>> > ----------------------------------------------------------------------
>> > There are only 10 types of people in the world:
>> > Those who understand binary, and those who don't
>> > ----------------------------------------------------------------------
>> >
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>>
>>
>>
>> --
>> Erik Schnetter <[email protected]>
>> http://www.perimeterinstitute.ca/personal/eschnetter/
>
>
>
> --
>
> Prof. Bruno Giacomazzo
> Department of Physics
> University of Milano-Bicocca
> Piazza della Scienza 3
> 20126 Milano
> Italy
>
> email: [email protected]
> phone: (+39) 02 6448 2321
> web: http://www.brunogiacomazzo.org
>
> ----------------------------------------------------------------------
> There are only 10 types of people in the world:
> Those who understand binary, and those who don't
> ----------------------------------------------------------------------



-- 
Erik Schnetter <[email protected]>
http://www.perimeterinstitute.ca/personal/eschnetter/
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