[Beowulf] Roadrunner shutdown

Nathan Moore ntmoore at gmail.com
Thu Apr 4 10:06:40 PDT 2013


Concur!  Porting code to BGL was more or less trivial.  "porting" to CUDA
means basically re-imagining how to parallelize your code.


On Thu, Apr 4, 2013 at 8:22 AM, Prentice Bisbal <prentice.bisbal at rutgers.edu
> wrote:

> On 04/03/2013 11:42 AM, Geoffrey Jacobs wrote:
> > On 04/03/2013 08:27 AM, Bret Stouder wrote:
> >> Prentice:
> >>
> >> For the money you could buy a lot more real computational cycles that
> last a lot longer than anything proprietary from IBM.  The reason the
> Origins have been out of production for a long time is the result of
> research moving to a commodity server platform.  Taken a look at what Cray
> offers lately?  Looks a lot like commodity.  If you are going to take the
> time to port code, it seems that a reasonable argument could be made to
> stay away from Blue Gene and port to Cuda or Phi.
> >>
> >> Bret
>
> Actually, that's a naive argument. The Blue Gene architecture uses
> standard MPI and support C, C++, Fortran, and Python, so any MPI
> compliant program written in any of those languages, which will also run
> just fine on a Blue Gene, with no porting necessary - just compile the
> code for the BG processors using GCC or the IBM XL compilers. IBM
> provides the ESSL and MASSV libaries that are optimized for the Blue
> Gene, but those are specified at link time, so I wouldn't really call
> that porting. Sure, there are tweaks you could use to really optimize
> your code for BG, but just doing the above will get you very far.
>
> In contrast, Cuda requires adding Cuda specific code to move data into
> and out of the device, and the sections to be run on the cuda processors
> needs to be rewritten in terms of cuda thread index, etc.
>
> For a large code, this could take a significant amount of labor, enough
> that it's conceivable in certain cases buying a Blue Gene could be
> quicker and more cost-effective than spending all the money on the labor
> to port your code to Cuda, test, optimize, test...
>
> In short, it's a lot more effort to port MPI-compliant code for Cuda
> than for a Blue Gene.
>
> I specifically didn't mention Phi because I do not know the details of
> porting/optimizing code for Phi.
>
> Prentice
>
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-- 
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Nathan Moore
Winona, MN
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