[Beowulf] massive parallel processing application required

Robert G. Brown rgb at phy.duke.edu
Thu Feb 1 15:26:17 EST 2007


On Thu, 1 Feb 2007, Peter St. John wrote:

> Moore's Law (which has grown in scope since Moore) applies to the aggregate
> effect of many technologies. Individual techs proceed in fits and starts.
> Predictions about FLOPS/dollar seem to be sustainable, but e.g. I predict a
> jump in chip density when the price point of vapor deposition manufactured
> diamond gets low enough (diamond conducts heat way better than silicon, and
> chips are suffering from thermodynamics limits).
>
> When AT&T divested, you could not get a decent telephone anymore; they were
> too expensive to make so well. Then after years of crummy phones, suddenly
> everyone had a cell-phone just like Captain Kirk's.
>
> Sure I want fiber optics to my house. But maybe the power company will carry
> data on the wasted bandwidth of power lines. Keep the faith :-)

I'm not certain and am too lazy to plot it out and check, but it seems
to me that communications has consistently lagged computation in the
time constant used in a Moore's-type law.  For CPUs it has been a fairly
predictable 18-20 month doubling time (at constant cost, connected to
the doubling time of VLSI for a long time but now more complex), which
means a factor of ten takes somewhere around five or six years to
accomplish.  That's three orders of magnitude in 15 to 20 years.  It
took those same twenty years to go from 10 Mbps to 1 Gbps ethernet, only
two orders of magnitude, at anything like constant cost.  Most things
I've read on the subject suggest that if anything the CPU/Communications
gap is widening, forcing systems designers to use methodology developed
for clusters and cluster communications even within a system (e.g.
Hypertransport).

Also, phone companies ARE gradually laying fiber everywhere, and while
they may or may not take it right up to your house they'll certainly
take it to your neighborhood, and maybe only "finish off" with copper.
It's just that installing fiber is expensive, and takes time, and
customers won't pay much of a premium for it.  They "have" to do it
anyway to compete with e.g. cable, and they are all doubtless running
scared in front of the possibility that nobody will own non-cell phones
anymore in a year or five so that either they are in a position to
deliver streaming media to the home in competition with the cable
company or they all belly right up in that market.  A bit of a race, in
other words, where they are ahead and behind at the same time.

It won't be done for computer users, though.  Not enough money in it,
and what there is is already developed.  Delivering entertainment, on
the other hand -- there aren't any visible upper bounds on what one use
there.  If you treble the bandwidth, you just make HDTV cheaper and
permit more stations and make it more feasible to deliver movies on
demands in real time -- bleep through 4-5 GB in 1 minute or two, then
display it at your liesure...

    rgb

>
> Peter
>
>
> On 2/1/07, Mark Hahn <hahn at mcmaster.ca> wrote:
>> 
>> > Not true.  Distributed computing is more and more mainstream.  I think
>> too
>> 
>> oh, one other snide comment about grid: I suspect the grid-fad could not
>> have happened without the fraud perpetrated by worldcom and others during
>> the internet bubble.  in those days, it was popular to claim that the
>> network
>> was becoming truely ubiquitous and incomprehensibly fast.  for instance:
>> 
>> http://www-128.ibm.com/developerworks/grid/library/gr-heritage/#N100A6
>> 
>> I don't know about you, but in the 6 years since then, my home net
>> connection has stayed the same speed, possibly a bit more expensive.
>> desktop/LANs are still mostly at 100bT, with 1000bT in limited use.
>> I do notice that grabbing large files off the net (ftp, RPMs, etc)
>> often runs at O(MBps) which is about a 10x improvement over the past
>> 10-15 years.  so the doubling time turns out to be more like 3 years
>> rather than 9 months.  in-cluster networking has improved somewhat
>> faster, but not dramatically so.
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-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu


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