The Math Behind PageRank

anaesthetica writes "The American Mathematical Society is featuring an article with an in-depth explanation of the type of mathematical operations that power PageRank. Because about 95% of the text on the 25 billion pages indexed by Google consist of the same 10,000 words, determining relevance requires an extremely sophisticated set of methods. And because the links constituting the web are constantly changing and updating, the relevance of pages needs to be recalculated on a continuous basis."

Comments

Bad summary

[Knights who say 'INT]

The article specifically says the PageRank eigenvector is only recalculated once a month, approximately. Even though Google uses some clever numerics to calculate the eigenvectors to a 25 billion by 25 billion matrix by iteration, it still takes several hours to finish.

Re:Pagerank is cool

[silentounce]

Interestingly enough, google thinks so, too.

Of course, yahoo has its own opinion.
 
Although, altavista seems to almost agree. Check the second non-advertised result.
 
I do find this amusing though. Third place, how humble.
 
I didn't expect such interesting results. The site with the search term in its url was tops for av and yahoo, but not google. Yahoo ranked the wiki entry above google, but av reversed that decision, google of course thought itself was more important than the wiki. Google's own reference site was number one in its own search and near the top in the other two, but pagerank.net wasn't even in the top 10 for google's search. I'm not sure what conclusions can be drawn from all that, but it is definitely food for thought.