On Wed, 2012-09-05 at 13:23 +1200, aaron morton wrote: > > I believe the question is why is the maximum 2**127 and not > > 0xffffffffffffffff oops - I got the wrong number of digits there. > The maximum is the size of the digest created by MD5. (I may be mistaken) - isn't the range of MD5 values 0 <= hash < (2**128) ? If you're dropping one bit to store as a signed integer to give 127 bits of entropy then it would be in the range: 0 <= hash < (2**127) but the range being checked is: 0 <= hash <= (2**127) > Does that answer the question? I meant that what the OP spotted was it's an inclusive maximum <= 0 <= hash <= 2**127 gives (2**127) + 1 different values, and is mathematically the clock-arithmetic (cyclic) group: Z/(2**127 + 1) [0] I _believe_ the issue is actually the other way around in AbstractHashedPartitioner (upper and lower bounds are exclusive) - but the comments are incorrect. i.e. both the code and the comments have off-by-one errors. {{{ if (i.compareTo(ZERO) < 0) throw new ConfigurationException("Token must be >= 0"); if (i.compareTo(MAXIMUM) > 0) throw new ConfigurationException("Token must be <= 2**127"); }}} The comments imply that 0 and 2**127 are both valid tokens (which they shouldn't be). The code does exclusive comparisons and excludes the value 0 though. Tim > [0] I believe the OP mistyped that as Z/(127+1) > > > ----------------- > Aaron Morton > Freelance Developer > @aaronmorton > http://www.thelastpickle.com > > On 3/09/2012, at 8:20 PM, Tim Wintle wrote: > > > On Tue, 2012-08-28 at 16:57 +1200, aaron morton wrote: > > > Sorry I don't understand your question. > > > > > > Can you explain it a bit more or maybe someone else knows. > > > > I believe the question is why is the maximum 2**127 and not > > 0xffffffffffffffff > > > > Tim > > > > > > > > Cheers > > > > > > ----------------- > > > Aaron Morton > > > Freelance Developer > > > @aaronmorton > > > http://www.thelastpickle.com > > > > > > On 27/08/2012, at 7:16 PM, Romain HARDOUIN > > > wrote: > > > > > > > > > > > Thank you Aaron. > > > > This limit was pushed down in RandomPartitioner but the question > > > > still exists... > > > > > > > > > > > > aaron morton a écrit sur 26/08/2012 > > > > 23:35:50 : > > > > > > > > > > AbstractHashedPartitioner > > > > > does not exist in the trunk. > > > > > https://git-wip-us.apache.org/repos/asf?p=cassandra.git; > > > > > a=commitdiff;h=a89ef1ffd4cd2ee39a2751f37044dba3015d72f1 > > > > > > > > > > > > > > > Cheers > > > > > > > > > > ----------------- > > > > > Aaron Morton > > > > > Freelance Developer > > > > > @aaronmorton > > > > > http://www.thelastpickle.com > > > > > > > > > > On 24/08/2012, at 10:51 PM, Romain HARDOUIN > > > > > wrote: > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > AbstractHashedPartitioner defines a maximum of 2**127 hence > > > > > > an > > > > > order of (2**127)+1. > > > > > > I'd say that tokens of such partitioners are intented to be > > > > > distributed in Z/(127), hence a maximum of (2**127)-1. > > > > > > Could there be a mix up between maximum and order? > > > > > > This is a detail but could someone confirm/invalidate? > > > > > > > > > > > > Regards, > > > > > > > > > > > > Romain > > > > > > > > > > > > > >