On Wed, Nov 21, 2012 at 01:38:37PM -0500, Matt Corallo wrote: > On Wed, 2012-11-21 at 16:15 +0100, Pieter Wuille wrote: > > On Wed, Oct 24, 2012 at 05:56:07PM +0200, Mike Hearn wrote: > > > I've written a draft BIP describing the bloom filtering protocol > > > extension developed by myself and Matt. > > > > > > https://en.bitcoin.it/wiki/BIP_0037 > > > > Two comments I made on the pullreq page, which are probably better > > discussed here: > > * The 0xFFFFFFFF/(n-1)*i seed value seems intended to result in large bit > > differences between the different hash function's seeds. Together with > > the tweak, > > however, the first and the last now get seeds tweak and tweak-1. I think > > something simpler like k1*i+k2*n+tweak is better (with k1 and k2 > > arbitrary large > > odd 32-bit integers). > Meh, sure, whatever...I dont really think the seed values matter > significantly (Murmur3 isnt that bad of a hash function...) (and the > original algorithm wont result in a significant bit difference between > the seeds in many cases).
Sure, it's nothing important, but it seems like it fails to do what it was intended for. How about just this: tweak + i*0xFBA4C795 (number optimized to give large seed differences for every tweak). If you want variation when changing the number of hash functions, just choose a different seed. > > Maybe the actual filter data in filterload can be made optional: > > if it is omitted, it's assumed to be all zeroes (though that would mean > > the size > > has to be specified). > > > I'm not sure here, if you are sending a filter just to use filteradd to > add things to it manually, you are doing something very, very, very > wrong... Though we could certainly do some kind of compressed bloom > filter encoding to allow for small filter loads (loading the few things > you need to filteradd right away) where you anticipate adding > significantly more filter elements down the road (can anyone even come > up with a case where you anticipate doing this?), the filter is small > enough (max 36kB) that I see little benefit for the large increase in > complexity (or is this another repeat of the merkle branch discussion?) It's probably not worth it for something that is max 36 kilobytes. If ever necessary, we can define a new message type that just lists a number of bits to be set in the server-side filter. For now, I agree that you should just send the filter as intended, and not expect to do many filteradds (though you should take the implicitly-added txids into accounted when computing the filter size). -- Pieter ------------------------------------------------------------------------------ Keep yourself connected to Go Parallel: DESIGN Expert tips on starting your parallel project right. http://goparallel.sourceforge.net _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
