🚀 go-pugleaf

In article <35896@lll-winken.LLNL.GOV> brooks@maddog.llnl.gov (Eugene
Brooks) writes:

>Supercomputers of the future will be scalable multiprocessors made of
>many hundreds to thousands of commodity microprocessors.  They will be
>commodity parts because these parts will be the fastest around and
>they will be cheap.  These scalable machines will have hundreds of
>commodity disk drives ganged up for parallel access.  Commodity parts
>will again be used because of the cost advantage leveraged into a
>scalable system using commodity parts.  The only custom logic will be
>the interconnect which glues the system together, and error correcting
>logic which glues many disk drives together into a reliable high
>performance system.  The CM data vault is a very good model here.

I think that it is interesting that you expect the same users who
can't vectorize their codes on the current vector machines to be able
to figure out how to parallelize them on these scalable MIMD boxes.
It seems to me that the automatic parallelization problem is much
worse than the automatic vectorization problem, so I think a software
fix is unlikely....

In fact, I think I can say it much more strongly than that:
Extrapolating from current experience with MIMD machines, I don't
think that the fraction of users that can use a scalable MIMD
architecture is likely to be big enough to support the economies of
scale required to compete with Cray and their vector machines.  (At
least for the next 5 years or so).  

I *do* think is that the romance with vector machines has worn off,
and people are realizing that they are not the answer to everyone's
problems. This is a good thing --- I like it when people migrate their
scalar codes off of the vector machines that I am trying to get time
on!!!

What is driving the flight from traditional supercomputers to
high-performance micros is turnaround time on scalar codes.  From my
experience, if the code is really not vectorizable, then it is
probably not parallelizable either, and scalable machines won't scale.
These users are going to want the fastest single-processor micro
available, unless their memory requirements are too big their ability
to purchase.

The people who can vectorize their codes are still getting 100:1
improvements going to supercomputers --- my code is over 500 times
faster on an 8-cpu Cray Y/MP than on a 25 MHz R-3000/3010.  So the
market for traditional supercomputers won't disappear, it will just be
more limited than many optimists have predicted.
--
John D. McCalpin - mccalpin@masig1.ocean.fsu.edu
		   mccalpin@scri1.scri.fsu.edu
		   mccalpin@delocn.udel.edu