[RC5] Active subspaces/random subspaces

Jim C. Nasby nasby at enteract.com
Sun May 10 23:28:22 EDT 1998


Edwin-
You are absolutly correct about the random subspace buildup problem. With any
luck, it is a non-issue though, since v3 _should_ be done and implimented
before we hit 50% on RC5-64. If it's not... well I guess I'd just have to go to
Duncan's apartment and club him over the head with a cattle-prod... :P

Mooo!
dB!
Chief distributed.net Duncan Motivation Officer :)

Edwin ten Dam wrote:

> Thus spoke the keyboard of Jim C. Nasby, nasbjim at charlie.cns.iit.edu on
> 06/05/98 17:45:
>
> >The basic reason for this is that the clients are coded to use the
> >current subspace+1 as the random subspace. It might be more space
> >efficient to issue out of random keyspaces (ie: switch from 0x64 to 0x65,
> >instead of 0x66), but it would also increase the dupe rate durring
> >switchover periods. Also, redoing random subspaces right now isn't an
> >option, since that would make a completed subspace the random one, meaning
> >that almost all randomly generated blocks would be dupes.
>
> Hmm. if I understand this correctly, there are a few problems with this.
> The random subspace (=current subspace+1) will never be finished at the
> same time as the current subspace; therefore you'll have to keep track of
> any subspace that once was random. So, (say curent subspace is even,
> random =current+1), for every step in current subspace we make, we'll
> gain an unfinished random subspace to keep track of. And what happens
> when we start finishing of these random subspaces? The then current
> subspaces (odd) will direct the random subspace to be the even subspaces,
> which are already done. Then there is a problem with take subspaces off
> the severs; by their nature randomly generated blocks will be from
> computers that have not been in contact for some time, they can't be
> relied on to be working in the appropriate random subspace.
>
> Maybe we should stick to the two current random subspaces (0x67 and 0x69)
> somehow, and when we get too many dupes in for one make that a regular
> one and take a new random subspace.
>
> cheers,
>
> Edwin
>
> Edwin ten Dam                                   etd at bigfoot.com
> School of Biomedical Sciences     -    University of St Andrews
> Irvine Building, North Street,  St Andrews, Fife KY16  9AL U.K.
> Phone: +44 1334 463404                   - Fax: +44 1334 463400
>
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--
Jim C. Nasby (aka Decibel!)                                  /^\
nasbjim at charlie.cns.iit.edu                                 /___\
Freelance lighting designer and database developer         /  |  \
Member: Triangle Fraternity, Sports Car Club of America   /___|___\

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