[Beowulf] Re: vectors vs. loops

Vincent Diepeveen diep at xs4all.nl
Wed May 4 01:00:15 PDT 2005

At 07:18 PM 5/3/2005 -0700, Greg Lindahl wrote:
>On Wed, May 04, 2005 at 02:40:17AM +0200, Vincent Diepeveen wrote:
>> In fact all that complaints about memory bandwidth IMHO is a lack of
>> understanding how hardware works.
>Allow me to be the first to congratulate you for being so willing to
>spend your valuable time to educate us all, and in fact the entire HPC
>-- greg

If an itanium2 montecito dual core clocks 2ghz and can theoretically
deliver therefore roughly 2 * 4 * 4 = 16 gflops, it's undeniable that this
means that cell starts at a potential of at least 16 * 8 = 108 gflops.

Having quite a bit more execution units IBM claims 256-320 gflop in fact.

Personally i believe in progress and that each few years faster cpu's come
on the market. Not trusting the companies to produce faster processors is
completely illogic.

Denying the fact that a cell processor starts at a factor 8 advantage in
number of gflops, simply because it is clocked nearly 2 times higher having
4 times more cores, is very unsportmanship.

What matters is what happens at the chip, just like network bandwidth
doesn't stop todays matrix calculations from using the full potential of
the todays chips, memory bandwidth obviously won't stop a CELL processor

Now we must see of course whether IBM can deliver it cheaply and in time,
or whether other manufacturers will show up sooner with a similar design
that's faster and above all cheaper. That still doesn't take away the
advantage a chip tens of times faster delivers is obvious when we realize
that far over 50% of all supercomputer system time goes to matrix type
calculations. All of which are embarrassingly parallel and easy vectorizable.

In fact the libraries are already vectorizing it more or less. It's just
doing more of the same thing faster now.

Denying that here is very unsportmanship towards all companies making
highend chips.


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