Author: Vincent Diepeveen
Date: 13:31:07 09/15/01
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On September 14, 2001 at 22:56:06, Pham Minh Tri wrote:
>I see that dual computers are expensive, not easy to own and still limited in
>power of computing.
>
>I wonder how good / possible if we use all computers in a LAN for chess
>computing. LANs are very popular and the numbers of computers could be hundreds.
LAN 1Gigabit /s or a slow 100mbit LAN?
>Even though a LAN is not effective as a dual circuit, but the bigger number of
>processors could help and break the limit.
>What do you think?
the problem is the hard work to make it. I had done some tests and have
a version of diep that nearly worked over the lan, but then i was confronted
with some huge slowdowns. Then i talked to Bob and i knew why.
note that 100mbit networks aren't 100mbit networks really. Even the fastest
cards i could not get more than 60mbit through a second.
a major problem is that if you try to get read info from it in a multithreaded
way that you get huge delays. Also multiprocessor the problem is exactly as
big.
Before you receive info over the network you are already hundreds of
milliseconds further. This is a major problem.
So a) you have huge overhead
b) you cannot communicate much
c) you will not be able to get systemtime on a big 100mbit network anyway.
d) the bigger the network the more chanceless you get a speedup at a
100mbit network.
e) where at networks with nodes being dual or quad getting a speedup is
already hard, at networks where nodes are single cpu getting a positive
speedup is nearly impossible.
I asked here some time ago for some volunteers and only got a few responses.
Regrettably the mailing list didn't work anymore so i lost most email
adresses, also not a single one has dual or quad machines. Getting a speedup
from a network 100mbit with single cpu nodes is nearly impossible for
an efficient program.
Of course for the nodes a second it might look great, but that's not my
goal.
So in short you CAN get a huge nps but if you measure speedup in the depth
you get at a dual versus a 8 node single cpu, then you will be hugely
dissappointed. The dual will outgun the 8 node anywhere if it's a 100mbit
network.
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