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Q3: How does Googlerank webpages?Mung ChiangNetworks: Friends, Money, and Bytes
Webpages form a network Links in text: since mid-20th century… Hyperlinks in webpages    Early 1990s: web, browser, portal...
Which webpages are more       important? Usefulness of ranking is hard to measure So rank by importance Quantify node impo...
General themesNetwork consists of   Topology: graphs, matrices   Functionality: what you do on the graphWe’ll see 3 matric...
Try 1Add up importance scores through incoming links
Try 2Normalize by the spread of importanceIs there a set of consistent scores?
Example
Calculation
What does Google do?Crawling the webStoring and indexing the pagesComputing two scores to rank pages per search   Relevant...
Remember vector and     matrix?
Matrix multiplication
Example
The first matrix
Iterations
Dangling nodes
The second matrixMandatory score-spreading
Too many consistent      scores
The third matrixRandomization
Pagerank algorithm
Example
Matrix
Iterations
PageRank result32481576
Parallel with DPCBoth are special cases of “power method” usingnon-negative matrix theory
The challenge of scaleNumerical linear algebra methodsA few more tricks
SEOHow to increase your website rank?How Google reacts?   Early 2011   May 2012
SummaryHyperlinked webpages form a networkConnectivity pattern provides a hint onimportancePagerank uniquely defines and e...
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Q3

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Transcript of "Q3"

  1. 1. Q3: How does Googlerank webpages?Mung ChiangNetworks: Friends, Money, and Bytes
  2. 2. Webpages form a network Links in text: since mid-20th century… Hyperlinks in webpages Early 1990s: web, browser, portal… Mid to late 1990s: search… Directed graph Huge and sparse N=40—60 Billion webpages out there… And very few links in/out of most webpages
  3. 3. Which webpages are more important? Usefulness of ranking is hard to measure So rank by importance Quantify node importance: Count the number of links? More important links point to this page? Turn a seemingly cyclic statmeent to characterize an equilibrium of a recursive definition
  4. 4. General themesNetwork consists of Topology: graphs, matrices Functionality: what you do on the graphWe’ll see 3 matrices and a model of the “searchand navigation” functionality
  5. 5. Try 1Add up importance scores through incoming links
  6. 6. Try 2Normalize by the spread of importanceIs there a set of consistent scores?
  7. 7. Example
  8. 8. Calculation
  9. 9. What does Google do?Crawling the webStoring and indexing the pagesComputing two scores to rank pages per search Relevant scores Importance scores
  10. 10. Remember vector and matrix?
  11. 11. Matrix multiplication
  12. 12. Example
  13. 13. The first matrix
  14. 14. Iterations
  15. 15. Dangling nodes
  16. 16. The second matrixMandatory score-spreading
  17. 17. Too many consistent scores
  18. 18. The third matrixRandomization
  19. 19. Pagerank algorithm
  20. 20. Example
  21. 21. Matrix
  22. 22. Iterations
  23. 23. PageRank result32481576
  24. 24. Parallel with DPCBoth are special cases of “power method” usingnon-negative matrix theory
  25. 25. The challenge of scaleNumerical linear algebra methodsA few more tricks
  26. 26. SEOHow to increase your website rank?How Google reacts? Early 2011 May 2012
  27. 27. SummaryHyperlinked webpages form a networkConnectivity pattern provides a hint onimportancePagerank uniquely defines and efficientlycomputes a consistent set of importance scoresWhich can be viewed as the dominanteigenvector of the Google matrix
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