🚀 go-pugleaf

In article <1990May23.041119.4359@ux1.cso.uiuc.edu> klietz@ux1.cso.uiuc.edu (Alan Klietz) writes:

   From: klietz@ux1.cso.uiuc.edu (Alan Klietz)
   Summary: Be not hasty to judge

   Aw, Marty don't write off CRI too fast.  While I admit that my sentiments
   about the YMP 2E are probably similar to yours, viz. divergence
   from CRI's strengths into areas of weakness, etc., they will survive
   based on outstanding technical merit (as usual), but in other areas.

CRI's outstanding technical merit walked out the door, packed his
bags, and went to Boulder. (;-)

   What areas?  Data parallelism, I think.   I am seeing deja-vu in the
   acceptance of the scientific computing community to DP as I saw in the
   acceptance to UNIX back in the mid-80's (cf. ETA discussion).  Those
   entities that embrace and push DP fastest will be the winners, while
   those that that continue with big iron vector boxes will be crushed
   by the Killer Micros and go the way of NOS Cybers and AOS Novas.

Data parallelism is an easy way to solve easy to parallelize problems.
It is a poor way to solve hard to parallelize problems.  As example, I
cite that the CM compilers do not run on the CM...  [Of course, most
of the problems in the "scientific computing" community are 'easy', so
that may not be an important point.  Linear algrabra exhibits good
locality of reference and relative independence of calculations.]

   CRI has embraced DP in a big way in only the last few months, I think.
   I have a pretty good idea, based totally on supposition, on what the
   teraflop YMP will look like (hint: think CM.)

I hope it isn't in the same big way they embraced "network
supercomputing" --- claiming to have invented something which on
analysis only means what other people call 'interconnectivity.'  If
that's true, they'll introduce a PARDO construct to Fortran and call
it data parallelism. (;-)

   I'm not selling my CRI stock anytime soon.

Me either. I can't get the money I put into it back, and I don't
need the loss on my taxes. (:-(  [CRI is now trading ~47, or about
half the average cost of CRI stock...]

But seriously.  For data parallelism to be fully effective one needs a
very high bandwidth low latency intercnonnect mechanism and problems
which exhibit high locality of reference.  The power of the processing
element isn't very important by comparison.  A large part of Thinking
Machine's success with the SIMD approach in the connection machine as
opposed to the price competitive MIMD approach of "hypercube" systems
is the very clever and rather quick routing of the machine, coupled
with the very low synchronization cost built into the lock step
approach of SIMD. Hillis, in his PHD thesis, argues that the
qualitative value of data parallelism only comes when a very large
number of processing elements can be effectively utilized in parallel.

CRI can build a data parallel machine in one of two ways.  It can
build a medium number of processor MIMD machine with near zero
synchronization cost and use the medium number of processors to model
the large number of processors Hillis postulates.  Or, it can build a
large number of processor systems.  In either case, doing this with a
MIMD system is a very difficult technical problem because of the cost
of synchronization.

CRI could possibly build a SIMD implementation of the Y/MP; that is a
Y/MP instruction set driven data parallel processor.  There are only
three things needed to do this that they don't currently have the
expertise for:

1) hardware
2) software
3) marketing (;-)

In fact, I can't even imagine such a machine running.  However, I've
been wrong about enough things that I'll try instead to imagine how
long it will take Crayless-Cray to produce the machine.

Let's see the C90 project has to be done first and then people freed
up.... (think, think, gaze at crystal ball:)

It would take CRI at least 10 years from today to introduce a usable
SIMD system ala connection machine with a processor count in the low
to medium thousands.

Can they survive that long without a follow on to the Y/MP, which will
be obsolete in 1994, if current industry trends of five year life
times are followed?

Marty
--
Martin Fouts

 UUCP:  ...!pyramid!garth!fouts  ARPA:  apd!fouts@ingr.com
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 MAIL:  2400 Geng Road, Palo Alto, CA, 94303

If you can find an opinion in my posting, please let me know.
I don't have opinions, only misconceptions.