AND You have again missed the point- I was using them to find out whether
there was any percentage in running any app on a beowolf- NOT to reduce the
speed of my machine - which incidently is an overclocked 333.Repeating
myself- if and only If under an Ideal situation - if there is a significant
performance difference between a MIMD implementation of any algorithm and
the SIMD one , ( IT MAY NOT be always faster- Taking the underlying h/w in
consideration) , Then one goes about trying
to use a Parellel architecture to get a speedup( I am talking only of the
need for speed - NOT fault tolerance , which is an entirely different
story). This is where The price performance ratio and user needs come in. If
you have enough cash - go in for a Close-coupled machine with the attendant
*High* cost. If you can get an acceptable level of performance ( by user
definition) using a loosely coupled architecture like the NOW( Network of
workstations ) then go for it.. A Beowolf is a software implementation of a
closely coupled system on loosely coupled hardware. The End result is
transparency - NOT a difference in speed with a NOW/POP ( The reason I told
you to look up the
defination is because typical examples using named pipes do NOT require a
Beowolf to run).
> Hi Shanker,
> You seem to have missed my point. Beowulfs are clusters fine -
> tuned for SPEED. SPeED is the word, nothing else. Nothing else.. we are
> not looking at accomodating heterogeneity in the avavilable machines to
Missed the point- I am unaware how you could get an Ideal case situation
otherwise? You have to justify the investment in resources to build a
beowolf.
> build up a Beowulf cluster. If SPEED is not optimised we can call it a
> "cluster", or a NOW or a POP.. but not a Beowulf.
Totally Incorrect- Speed has nothing to do with terminology w.r.t the above
statement( It has to an Extent otherwise)
> Then again, who cares
> about definitions. ?
EVERYTHING depends on definations-Otherwise I could call a simple network
using diskless workstations using NFS a beowolf . Thet is what
differentiates a scientist from a dreamer- The lack of clarity in vision
which a lack of precise defination brings.
> I do not get your idea of running a VM on multiple machines to
> build a cluster.
> (A) Implementations of MPICH/PVM on Windows are flakey or broken.
> Do not even try to use them ;)
I Wasn't . However- This does defeat your need for heterogenety -:-)
> (B) Running a VM on multiple machines _will_ slow down your
> performance.
Who is ( Just by itself)?These exist to make higher level tools /resources
like monitors ( the semaphore one) available. The trick is to find an
algorithm for say Matrix Multiplication in parellel where the subalgorithms
have very little interaction( They exist _ have to give an exam on them in
my sem exams!). With sufficient VM's , a significant speedup could be
managed - Sufficient being the keyword. ( Space - time complexity)
> (C) Running 450 MHz chips with a 10Mbps backplane is NOT
> Beowulfing... throwing to the winds all the fundae
> surface to volume ratios of orthogonal tile graphs.
Finally you are getting somewhere-
1. That is the precise reason You need to do some benchmarks to JUSTIFY
making the Beowolf. The entire point of this discussion from my side has
been directed towards that. Processors will keep getting faster and This
means newer MIMD algorithims which need fewer interactions/Messages to pass
are needed. Once you have got such a situation - even multiple 733 Mhz m/c
on such a network will be useful. The entire thing boils down to designing
something to your needs.
BTW the 10 MBPS limit is due to a design of a 2.5 km LAN- Reduce distance
and your speed increases- But you know it anyway!
> An interesting question is "What is the universal metric of
> performance ?"
>
> As far as __testing__ MIMD / SPMD applications on NOW, VM should
> suffice , provided you hand code explicit socket based libraries for
> message passing or MAPI stuff, but I reassert that is not going to be a
> Beowulf, as far as the speed factor is concerned.
Wouldn't it be better to optimise the VM rather then throw it away and
reinvent the wheel? Remember , You will have to do a lot of work to get
something useful up and then you would have thrown away the advantages of
the collabrative work that has already gone into the VM and Message passage
system.( and not be able to take the advantage of apps written for the VM
based architecture)
> One more thing, Transputers don't give you performance factors
> anywhere near to a properly tuned NOW. So there is no point in sticking
> with them. Also,if you have debugged in OCCAM, you will realize why
> this immeasurable hate ;)
Given Transputers which are sufficiently fast- I disagree. A Transputer
system is closer to a closely coupled system than a NOW. You CANNOT beat the
speed of a Closely coupled system with a loosely coupled system( With
comparable hardware) . They can run a far larger number of algorithms than a
NOW . Their drawback is their cost and their complexity. Given a choice
between an 8 way system and 8 machines - I would pick the 8 way system
anyday ( As far as speed goes)
Tel:91-033-4710477>
> Department of Computer Science and Engineering
> Jadavpur University Calcutta, India 700 032
>
> All the world's a stage..
> And I am acting tonight
> C - the difference : http://www.eskimo.com/~scs/C-faq/top.html
>
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