On Thu, Jun 01, 2006 at 01:11:25AM -0600, Brian F. G. Bidulock ([EMAIL PROTECTED]) wrote: > Evgeniy, > > On Thu, 01 Jun 2006, Evgeniy Polyakov wrote: > > > On Thu, Jun 01, 2006 at 12:46:08AM -0600, Brian F. G. Bidulock ([EMAIL > > PROTECTED]) wrote: > > > > Since pseudo-randomness affects both folded and not folded hash > > > > distribution, it can not end up in different results. > > > > > > Yes it would, so to rule out pseudo-random effects the pseudo- > > > random number generator must be removed. > > > > > > > > > > > You are right that having test with 2^48 values is really interesting, > > > > but it will take ages on my test machine :) > > > > > > Try a usable subset; no pseudo-random number generator. > > > > I've run it for 2^30 - the same result: folded and not folded Jenkins > > hash behave the same and still both results produce exactly the same > > artifacts compared to XOR hash. > > But not without the pseudo-random number generation... ?
How can I obtain (2^30)*6 bytes of truly random bytes? > > Btw, XOR hash, as completely stateless, can be used to show how > > Linux pseudo-random generator works for given subset - it's average of > > distribution is very good. > > But its distribution might auto-correlate with the Jenkins function. > The only way to be sure is to remove the pseudo-random number generator. > > Just try incrementing from, say, 10.0.0.0:10000 up, resetting port number > to 10000 at 16000, and just incrementing the IP address when the port > number wraps, instead of pseudo-random, through 2^30 loops for both. > If the same artifacts emerge, I give in. I've run it with following source ip/port selection algo: if (++sport == 0) { saddr++; sport++; } Starting IP was 1.1.1.1 and sport was 1. Destination IP and port are the same 192.168.0.1:80 Jenkins hash started to show different behaviour: it does not have previous artefacts, but instead it's dispersion is _much_ wider than in XOR case. With following ip/port selection algo: if (++sport == 0) { //saddr++; sport += 123; } I see yet another jenkins artefacts, but again different from previous two. But each time both folded and not folded hashes behave exactly the same. > Can you show the same artifacts for jenkins_3word? What should be used as starting point there? If I use 0 it is the same as jhash_2words(). If I use 123123 - artefacts are the same, just slighly shifted (I tested only the latest test above though). Looking into the code we can see that jhash_2words() is jhash_3words() with zero "C" value, so it will show the same nature. -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html