[Beowulf] Win64 Clusters!!!!!!!!!!!!

[Jim Lux]

At 01:29 PM 4/10/2007, Mark Hahn wrote:
>>It was PVM that enabled true message passing parallel code to be written
>>that made a pile of machines (be they Alphas, simple PCs, Sun
>
>I'm not disagreeing, but wonder why PVM is basically extinct now.
>that is, why was MPI considered an improvement/replacement?

I will speculate that it's because "message passing" as a 
interprocess and interprocessor communications model  came around 
first, and had a bit more traction.  There are always those hardy 
souls willing to partition the problem themselves as opposed to some 
sort of magic virtual memory/machine model doing it for them.

And, there were extensive libraries to divvy up the work using a 
message passing layer underneath.  Why.. sitting here on a shelf in 
my office (as a curiosity with which to beat young 
whippersnappers/early career hires who think they've just invented 
such things) is a set of lecture notes and manuals for CCLISP (ah 
yes.. the glory days of LISP for everything) as well as all the math 
libraries for cluster computation for matrix math, etc.

Those are all based on much earlier message passing work of the 
DECnet era.. I have a textbook on distributed computing from 1980 
(Weitzman, "Distributed Micro/Minicomputer Systems") which describes 
all those schemes (DEC PCL-11B? IBM DPPX? TRW DDP? etc.), both shared 
memory and message passing oriented (note that this book explicitly 
doesn't talk about supercomputers, which, obviously, also had shared 
memory/crossbars/etc). It even mentions that new-fangled experimental 
interconnect from Xerox called Ethernet, although it talks about a 
variety of variants that might fix some of the observed problems....

Anyway.. the message passing schemes would work over "really slow" 
links (albeit at reduced performance) and would at least be 
functional for decomposing a problem.  I would cringe to think of 
trying to do a PVM style task with 56,700 bps interconnects between 
processors.  Remember, you're dealing with node processors the like 
of PDP11s and 1 microsecond cycle times (I'd have to drag out my 
11/70 manual to see for sure).. Pushing out a megabit per second on 
ANY interface would have been a chore.

James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875