Subject: Re: Response to Grassl - scalability

From: Vladimir Getov <[email-masked]>
Date: Wed, 5 Jan 94 17:16:27 GMT

Scalability
-----------
> 
> >MPP is a generic name.  The US agency ARPA is trying to change the use
> >of the lable "MPP" to Scalable MuliProcessor (SMP).  I object to the
> >latter label because there is not an adequate defition of "scalable".
> 
>     I agree, and indeed I object to both MPP and SMP, as we don't know 
>     what either Massive or Scalable is supposed to mean. Everything is 
>     scalable to some extent, and nothing is infinitely scalable. 
>     The only sensible question is by how much and in what manner does
>     a particular design scale when more processors are added. A very
>     complex question which is rarely properly answered, if indeed the
>     answer is known at all.  I will try to avoid these terms, but will
>     probably have to mention them.
> 
I think we should emphasize mainly on program (benchmark) scalability.
Generally speaking, increasing the problem size we also increase:

(1) the memory requirements of the code;
(2) the calculation requirements (the flop count) of the code;
(3) the communication requirements (if any) of the code (the total
    number of messages and their length).

I would propose that these three could be recognized by PARKBENCH as the
main scalability characteristics of our benchmarks. They should have
their estimated or calculated values (or a formula, if these values 
depend on the number of nodes/processors) for the three standard problem
sizes (test problem size, moderate size problem, and grand challenge
problem) in the individual README files (see the minutes of the 4th
PARKBENCH meeting in August, 1993). I believe that this information would
allow us to draw conclusions about the scalability of parallel computers
after taking the benchmark measurements.

... - Other stuff deleted - vsg

>                     Roger Hockney
Vladimir Getov