[Beowulf] Has anyone actually seen/used a cell system?

Vincent Diepeveen diep at xs4all.nl
Mon Oct 2 12:18:58 EDT 2006


Actually Gofer also compiles to C.

That automatic translation had a cost a factor 200 in speed though.

There was some claim of factor 50 (but that was based upon a
very inefficient C compiler where it worked for, namely turbo c),
supported on paper. But that was old paper. I benched it at factor 200.

Even if you work hard and get it down to factor 50, still that's a factor 50 
loss
for nothing.

Cilk for example is just a few functions you can use from *inside* C code.
How is sequoia going to beat Cilk?

Just using a 'library' from within C/C++ is always better than ANL that 
indirectly compiles,
thereby losing big efficiency.

Vincent
----- Original Message ----- 
From: "Andrew Shewmaker" <agshew at gmail.com>
To: "Vincent Diepeveen" <diep at xs4all.nl>
Cc: <J.A.Delcorso at larc.nasa.gov>; <beowulf at beowulf.org>
Sent: Monday, October 02, 2006 4:03 PM
Subject: Re: [Beowulf] Has anyone actually seen/used a cell system?


> On 10/2/06, Vincent Diepeveen <diep at xs4all.nl> wrote:
>> Not wanting to sound too negative, but total nonsense concept.
>>
>> First of all this 'sequoia' claims to be a new programming language.
>> Meaning it'll take a year or 30 until some good compilers for it are 
>> there,
>> provided someone is going to support it.
>>
>> Which isn't going to happen.
>
> Like many new programming systems, it compiles to C.
>
>> The parallellization basically is based upon complex assumptions for
>> programmers. So for programmers they don't actually make it easier than
>> trivial parallellization is via C/C++ function calls.
>>
>> The sequoia parallellization basically is simplistically over for loops 
>> that
>> a programmer himself can trivially parallellize too.
>
> Sequoia allows the same source to compile and run on systems with
> very different memory hierarchies.  It uses MPI on clusters and DMA
> on the Cell.  It also manages overlays on the Cell.  Do you consider a
> portable runtime system that manages overlays and streams data
> asynchronously trivial to implement?
>
>> Further the optimization of sequoia simply doesn't happen. They assume
>> "kernel libraries" solve the problem. Interestingly it mentions 
>> explicitly:
>>
>> "if kernel libraries could be obtained, such as FFTW and the intel MKL 
>> for
>> PCs, or the IBM SPE matrix library for Cell, we call these libraries from
>> Sequoia leaf tasks".
>>
>> In short if some algorithm has not been implemented for sequoia, sequoia 
>> is
>> unusable.  Others may do the work as usual to promote sequoia.
>
> As I understand it, the leaf tasks can be written in C, Fortran, or 
> whatever.
>
> Saying Sequoia is unusable is like saying that MPI is unusable.
>
> -- 
> Andrew Shewmaker
> 

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