On Mon, Aug 10, 2015 at 1:11 PM, nusenu nusenu@openmailbox.org wrote:
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Hi,
https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n2028
If 3 or more authorities provide a Measured= keyword for a router, the authorities produce a consensus containing a "w" Bandwidth= keyword equal to the median of the Measured= votes.
a random sample from recent votes:
grep 37.59.38.117 -A 3 *|grep Measured w Bandwidth=6869 Measured=7570 w Bandwidth=6869 Measured=15500 w Bandwidth=6869 Measured=18100 w Bandwidth=6869 Measured=30500
Tor says the median value is 15500
2015-08-10-16-00-00-consensus: w Bandwidth=15500
but the median of these 4 values is actually: (18100+15500)/2 = 16800 no?
Has tor a different definition of 'median' and simply takes always the second ordered measurement vote out of 4 votes or is there a bug in the spec or implementation?
There's one misplaced throwaway sentence in dir-spec.txt:
" All ties in computing medians are broken in favor of the smaller or earlier item. "
We should bring this, and probably other things, into a "definitions" section earlier in dir-spec.txt. Patches welcome. ;)