[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Re: [tor-bugs] #6232 [Analysis]: Make entropy-over-time graph
#6232: Make entropy-over-time graph
-------------------------+--------------------------------------------------
Reporter: arma | Owner:
Type: enhancement | Status: needs_review
Priority: normal | Milestone:
Component: Analysis | Version:
Keywords: | Parent:
Points: | Actualpoints:
-------------------------+--------------------------------------------------
Comment(by phw):
Replying to [comment:9 phw]:
> A clarification for the math which changed between the initial code and
my update:
>
> Assume the early days of Tor, where we have only a few relays in the
consensus. In fact, it's 7 relays with the following bandwidth:
> `[1, 1, 2, 2, 2, 3, 4]`
>
> The old code determined the total bandwidth (15, the sum of all
bandwidths in the list) and calculated:
> `1/15 * log2(1/15) + 1/15 * log2(1/15) + 2/15 * log2(2/15) + 2/15 *
log2(2/15) + 2/15 * log2(2/15) + 3/15 * log2(3/15) + 4/15 * log2(4/15)`
>
> The problem is the probabilities. E.g., for the value '1', we expect a
probability of 2/7 (There are two instances of '1' in all 7 values) and
not 1/15.
>
> The uploaded version fixes that. It builds a hash table of the form: `{
bandwidth_value => observed occurrences }`. Then, it iterates over the
hash table, adds up the result and we have the entropy.
Note that the above is probably '''not''' what we want. It calculates the
entropy based on the probability of a '''bandwidth''' instead of a
'''relay''' being selected. So gsathya was right all along.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6232#comment:14>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
_______________________________________________
tor-bugs mailing list
tor-bugs@xxxxxxxxxxxxxxxxxxxx
https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-bugs