[Beowulf] Larrabee - Mark Hahn's personal attack
prentice at ias.edu
Fri Jan 27 11:34:41 EST 2012
On 01/27/2012 11:12 AM, Vincent Diepeveen wrote:
> And both are seem failures from user viewpoint, maybe not from intels
> income viewpoint,
> but from intels aim to replace and/or create a new long lasting
> that can even *remotely* compete with other manufacturers,
> not to mention far too high pricepoints for such cpu's.
This argument is ridiculous. Just because two completely different
technologies (architectures) both fail, doesn't make them similar.
That's like saying a Ford Edsel and Pontiac Aztek are similar cars.
> Assuming you're not completely born stupid, i assume you will realize
> that IN ORDER to run
Calling someone "completely born stupid" is unacceptable behavior.
> most existing x64 codes, it needs to have cache coherency, and that
> it always has been
> presented as having exactly that.
> Which is one of reasons why the architecture doesn't scale of course.
Cache-coherent systems don't scale well? Really? SGI Origins were ccNUMA
systems, and they scaled well.
> Well you can forget about them running your x64 fortran codes on it
> at any fast speed.
> You need to total rewrite your code to be able to use vectors of
> and in contradiction to GPU's where you can indirectly with arrays
> see each PE or each 'compute core'
> (which is 4 PE's of in case of AMD-ATI that can execute 1 double a
This argument makes no sense in the context of this discussion. You
need to do a significant rewrite of your code to take advantage of GPUs,
too, so how are GPUs better?
> Such lookups are a disaster at larrabee - having a cost of 7 cycles
> for indirect lookups,
> so you really need to use vectors.
> Now i bet majority of your oldie x64 code doesn't use such huge vectors,
> so to even get some remote performance out of it, a total rewrite of
> most code is needed,
> if it can work at all.
> We can then also see the insight that GPU's are total superior to
> larrabee at most terrains and
> most importantly at multiplicative codes.
> As you might know GPU's are worldchampion in doing multiplications
> and CPU's are not.
> Multiplication happens to be something that is of major importance
> for the majority of HPC codes.
> Majority i really mean - approaching 90% at the public supercomputers.
I'm at a loss for words...
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