Beowulf Questions

Randall Jouett rules at
Fri Jan 3 21:59:57 PST 2003

Hello Donald, and thanks for the response.

Donald Becker wrote:
> Various ports of POV-Ray are available for PVM and MPI, with a very wide
> range of quality and performance.
> We distribute a version of POV-Ray specifically ported for our cluster
> system and BeoMPI. Our POV-ray port is interesting because
>     It transparently uses all available cluster nodes, and works even if
>      that number is '0'.

I like this.

>     It does all of the serial setup and run-time I/O on the front end
>       machine (technically, the MPI rank 0 node).  This minimizes
>       overall work and keeps the POV-Ray call-out semantics unchanged
>     It does the rendering only on compute nodes (except for the N=0 case). 
>     It complets the rendering even with crashed or slow nodes.

Ah. So it redistributes the work, huh? Kewl. Sounds like
somebody at your place of employment has a great abstract
mind, being able to encompass all variables, yet the end
solution seems concrete and directed toward the individual
user. Too kewl.

>>* Is there a beowulf setup out there setup specifically
>>   for random-number generation, with its main focus on
>>   generating "truly random" numbers, if you can say that
>>   synchronus, clock-based computers are capable of generating
>>   truly random numbers :^). If so, has a cluser of this type been
>>   used in encryption and decryption purposes.
> This is trivial.  Once you get a good a serial pseudo-random number
> generator, you can use a cluster to generate more.

That's what I was thinking. Can you say 1 billion bits of
RSA encryption? I knew you could :^). My only worry here is
that with a few hundred thousand nodes, would the NSA be able
to decrypt stuff relating to national security? That is, could
the government actually afford to purchase on-site equipment
that could keep up with P2P, Internet-based clustering, if you
will? Peronsally, I think they'd have to jump in on the bandwagon
with everyone else, yet with the current level of "Big Brother
is wathcing us all" attitude floating around, I seriously doubt
that people would knowingly allow them to use their free cycles
for decryption without some mega-serious watch-dogging geeks
watching their every move.

>>* Is anyone working on beowulf clustering based on trusted-host
>>   computing? That is, instead of having a local cluster of
> This wouldn't be a Beowulf cluster.  (It's a stretch to
> call it a cluster at all.) Cycle scavenging is different
> concept, and it only to a tiny percentage of problems.

Ah. Ok. Thanks for the info. OTOH, one can't help to wonder
if this isn't the future of computing, especially when we
consider the fact that almost all of our appliances we'll
be using in the near future will be network aware. For instance,
my computer determines that a particular task/process is very
CPU intensive, and the best solution to the problem would be
to use more processors in a parallel fashion to obtain the
result. Wouldn't it make perfect sense for the system to set
itself up as a master node and subdivide the task at hand to
various network-aware devices/computers, such as the unused
television or coffee pot? :^). Also, if the "local cluster"
of household machines isn't up to the computation, wouldn't
it also make sense that the master/root node would then go
out and ask its/your nextdoor neighbor if it can steal a few
cycles, too, branching out further if necessary? Basically,
I'm thinking along the lines of a power-grid like setup here.

I guess what I'm really trying to say here is this: do all
nodes "have" to be on site to be considered a beowulf cluster?
Personally, I don't think so, especially if we consider the
fact that in the not-too-distant future, networking speeds
will be up to snuff with the various tasks at hand. With these
concepts in mind, I'll step out on a limb here and say that it
might actually be very advantageous to live in a highly-congested
area, like in an apartment complex or next to a busy freeway. Living
in an area that encompasses both would flat-out rule :^).

BTW, when I say "living next to a freeway would be advantageous,"
I'm talking about using unused cycles from various WiFi-connected
cars :^). Futuristic? At this point in time, most definitely; however,
I'm sure that most of us here see something as left-field as this
eventually happening, and, IMHO, someplace like this is exactly
the place I want to be before the rest show up.

As a side note, I found something on the web last night called
"GreenTea," which is a P2P-like "operating system" setup around
Java. Interesting concept, portable, and I can see a system like
this taking off fairly soon. OTOH, I think interpreted languages
and environments have a bit further to go before they'll start
pushing compiled languages aside, though.Eventually, they should
take over,although I seriously doubt it will be anytime soon.

> (People have heated discussions about cluster I/O performance and
> communication latency.

I bet they do, and, quite frankly, it's very understandable,
especially when we all start to consider the major drawbacks
of using Ethernet-based NICS for message passing. OTOH, it is
cheap, are there are certainly various applications that lend
themselves nicely to using this type of environment.Personally,
I'd be more worried about things such as node stability, algorithms, 
code profiling, algorithms, and maybe even looking into writing
various time-critical subroutines in assembly. IMHO, this would
time much better spent :^). Not only that, but if we were to
nit-pick the beowulf model to death, I think we'd come to the
conclusion that using multiple processors on a real buss would
be a much better way to go, although I'm sure we'd all eventually
wind up designing something that resembles a 1.5 million dollar
Sun or IBM system :^).

>(With cycle-scavenging, these are orders of magnitude worse.)

Agreed. OTOH, this will eventually change, and linear-progressive,
"next logical step," fringe-level computing is where I like spending
my man hours. Unfortunately, though, we all have bills to pay and
rationilaztions to make about the current level of real-world computing,
so let's just say that I'm a bit flexible in this particular area :^).

BTW, my main level of interest in this particular field is system
administration and a bit of code cranking. Having done both for
years, I find network administration much more relaxing -- believe
it or not! :^) Not only that, but having a decent level of hardware,
electronics, telecommunications, and programming knowledge has to be 
benificial when administrating something like a beowulf cluster. 
Hopefully, the road to learning this particular model of computing won't
be too time consuming. OTOH, I'm sure the infamous Murphy will rear
his ugly head somewhere along the line :^).

Thanks for your time and remarks, Donald -- it is much appreciated!


Randall Jouett
Amateur Radio: AB5NI

I eat spaghetti code out of a bit bucket while sitting at a hash table!


Is it just me, or do others find it annoying that the current
version of Mozilla doesn't have spell-checking capability? BTW,
this is a semi-shrewd way of saying, "Please disregard all spelling 
errors, and please send all complaints to /dev/null :^).


Anyone out there try Plan 9 in a beowulf environment? As a layman
and at first glance, it does seem to be well suited to the tasks
at hand.

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