>From: "Brian J. Beesley" <[EMAIL PROTECTED]>
>To: "Geoffrey Faivre-Malloy" <[EMAIL PROTECTED]>
>CC: [EMAIL PROTECTED]
>Subject: RE: Mersenne: The recent popularity of Factoring
>Date: Sun, 26 Mar 2000 07:39:15 -0000
>
>Geoffrey Faivre-Malloy wrote:
Stuff that we've already gone over and dabated for a few days.
Regarding factoroverride=, Brian stated:
>I'd call it an "unwanted feature". George, I think perhaps the easy
>way to handle this would be to check "UsePrimeNet" and refuse to
>execute AdvancedFactor assignments if UsePrimeNet=1.
Seems perfectly reasonable, or maybe allow it only if the difference between
the override value and the default depth is no more than two bits. One can
still make a case, however, that this will result in other users getting
exponents that will take nearly as long to run and have a greatly reduced
chance of finding a factor.
>
>I appreciate the point about slower machines. One way to deal with
>this would be a few small changes to Prime95, and a small enhancement
>to PrimeNet.
>
>It could go something like this:
>
>Prime95 would have a new parameter for the maximum elapsed time for a
>factoring assignment. When it completes to a depth of n bits, before
>going on to (n+1) bits it checks if the max elapsed time would be
>exceeded. If so, it reports "no factor found to 2^n", signals
>PrimeNet that it is abandoning work on this exponent & goes on to the
>next assignment. (I think that this is purely client end so far,
>since there is already a mechanism to return an unwanted assignment,
>both in the manual testing pages and invoked from "Quit Gimps".)
I think the date should be user-modifiable, but only as a whole number of
days. There is no reason why a person would not be able to have a machine
doing factoring for one day (or three days, even, if it's a business
machine)
>
>When requesting factoring assignments, Prime95 would tell PrimeNet
>the maximum number of bits pre-factored it was prepared to accept
>assignments for (this could be calculated approximately from the max
>factoring assignment time parameter) . This requires a change to the
>server as well as to the client to accommodate, since the server
>would have to scan down the list of available factoring assignments
>until it found a suitable candidate.
And what of those assignments that have already been pre-factored? I guess
we might assume that there will be enough naive novice users coming in who
will be able to deal with them though...
>However it is also possible that slower machines with reasonable
>amounts of memory could find a role running P-1 assignments, when
>they become available. Note that this is dependent on a major change
>to the server software, so maybe now is a good time to specify the
>relatively minor change needed to accommodate a scheme similar to the
>above.
I feel I'm still a touch new to comment on this part.
>A more general & more secure method of preventing the type of problem
>exposed by this incident would be to have the server enforce a quota
>for the maximum number of assignments issued to any user/computer id
>combo in a particular time interval e.g. 20 per day. Yes, this could
>still be got round by anyone determined to cause mischief by changing
>the computer id and grabbing another bunch of assignments, but it
>would be effective against accidents.
>
>
>Regards
>Brian Beesley
I still feel that 20/day is rather liberal. I have a P3-600, nearly
top-of-the-line now, and when I was doing factoring 24//7 it was rare to
finish two assignments in a day; I never finished more.
Regards
Nathan
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