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PageRank
Whenever we need to search for a result on Google, this one of the most famous algorithm used.
First we take some pages and all the links available on that page linking to the other gathered pages:
p1, p2, p3, p4, ..., pn
# Links found on the page
p1:
- a1 -> p2
- a3 -> p4
...
- al -> p8
p2:
...
Then we make an oriented graph where all the points are pages
and links are arrows pointing to the landing page
Variables
B_p: Set of pages that backlinks top|a|: Cardinality ofa| Number of outgoing links froma
Formula
rank_k(p) = \sum_{a \in B_p}\frac{
rank_{k-1}(a)
}{
|a|
} \in [0, \dots, 1]
Here the state is composed of all ranks for our gathered pages.
If | rank_k(p) - rank_{k-1}(p)| < \epsilon we will stop
iterating.
At time k = 0 all pages have the same importance that is
rank_0(p) = \frac{1}{n}