On Fri, Oct 03, 2003 at 11:37:35PM +0000, thong wrote: > Martin Stone Davis <[EMAIL PROTECTED]> writes: > >Ian Clarke wrote: > >> I still don't have my head around this fully yet, but I think the core > >> flaw in your proposal is that it assumes that, for a given key, the > >> pSuccess values of repeated requests to the same node are independent, > >> but they are not. After the first failure, pSuccess for that node drops > >> to 0. > > > >Hand-wavy explanation: When trying to ask "how long will it take this > >one node to give us a 1 unit of data?" we don't have to be concerned > >about how our opinions about pSuccess will change in the future. All > >that matters is the true value itself. Since we don't know the true > >value, the best we can do is use our current opinion of the true value. > > I think the basic problem is as follows. In Martin's model, you > repeatedly query the same node again and again. Sometimes it decides > to give you data (with probability pSuccess), sometimes it decides not > to (with probability pFailure). The rate at which you can issue > queries depends on how long the node takes to get back to you > (tSuccess or tFailure, respectively). Martin then picks the node that > gives the greatest throughput. > > There are two difficulties here. First, we are only interested in > getting the data once, not lots of times. So we really want to > minimize the time to the first success, not maximize the number of > successes over time. > > Second, once the node returns failure, that means it can't find the > data. There's no point in asking again, because it will again say no. > Or will it? Maybe we *should* admit the possibility of asking the > same node twice - downstream network conditions might change. After > all, that's exactly what you do on your own node when requesting data. > If you don't find it, you try again.
DataNotFound cache. A.k.a. failtable. > > theo > > > -- > Theodore Hong Dept. of Computing, Imperial College London > [EMAIL PROTECTED] 180 Queen's Gate, London SW7 2BZ > PGP key: http://www.doc.ic.ac.uk/~twh1/ > > _______________________________________________ > Devl mailing list > [EMAIL PROTECTED] > http://dodo.freenetproject.org/cgi-bin/mailman/listinfo/devl -- Matthew J Toseland - [EMAIL PROTECTED] Freenet Project Official Codemonkey - http://freenetproject.org/ ICTHUS - Nothing is impossible. Our Boss says so.
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