Subject:
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Re: Brainstorms GUID
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 13 Aug 2002 00:15:04 GMT
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Original-From:
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Steve Baker <SJBAKER1@AIRMAIL.nomorespamNET>
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Reply-To:
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sjbaker1@airmail.NOSPAMnet
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Viewed:
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838 times
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Bruce Boyes wrote:
> Here's the issue I was addressing:
>
> How do you guarantee that two vendors won't produce the same 128-bit
> pseudo-random number? If they use the same algorithm they will produce
> the same series of "random" but not unique numbers, unless you can
> guarantee that they use different seeds. Thirty two bits would give you
> four billion numbers, I'm wondering why you chose 128.
Presuming they can use different seeds, 32 bits is one chance of collision
every 4,294,967,296 attempts. If they don't have random seeds then it doesn't
matter a damn how many bits you have.
The chances of collision on each reboot go up rapidly with the number of
units you have connected though. For two units, it's one in 4 billion - but
for N units, there are N(N-1)/2 ways...it gets big quickly.
However, even if you have 6 nodes, (15 ways to get a collision) then the
odds are still one in 286331153 each time you reboot. That's enough to let
you reboot once a second, day and night for nine years with a reasonable
expectation of just one failure in all that time. Failure of your reset
button is much more likely!
However, if you were contemplating truly HUGE systems with 10,000 connected
parts - then there are about 50 million ways they could generate a pair of
matching random 32 bit numbers - so your system will screw up roughly once
in every 85 reboots - which would be enough to be annoying.
But a 128 bit number seems like overkill.
----------------------------- Steve Baker -------------------------------
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Message is in Reply To:
 | | Re: Brainstorms GUID
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| (...) Maybe I completely missed the point myself? I like your idea of intelligence so small it can fit into a brick, and then tie into upper levels of higher intelligence. That sounds like true distributed processing (a good thing) to me. Here's the (...) (22 years ago, 12-Aug-02, to lugnet.robotics)
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