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Lecture 17

Lecture 17. Search Engines & Map Reduce Project meeting sign up: http ://goo.gl/ SauqD. Page Rank Example. A. B. C. D. A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0. Page Rank Example. A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0. Round 0

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Lecture 17

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  1. Lecture 17 Search Engines & Map Reduce Project meeting sign up: http://goo.gl/SauqD

  2. Page Rank Example A B C D A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0

  3. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 3 links to A

  4. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 3 links to A B links to 2 docs

  5. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 3 links to A B links to 2 docs C links to 3 docs

  6. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 1/2 = 1.33 3 links to A B links to 2 docs C links to 3 docs D links to 2 docs

  7. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 1/2 = 1.33 PR(B) = 2 links to B

  8. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 1/2 = 1.33 PR(B) = 1 + 1/3 = 1.33 2 links to B

  9. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 1/2 = 1.33 PR(B) = 1 + 1/3 = 1.33 PR(C) = .5 1 link to C

  10. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 0 PR(A) = 1, PR(B) = 1, PR(C) = 1, PR(D) = 1 Round 1 PR(A) = 1/2 + 1/3 + 1/2 = 1.33 PR(B) = 1 + 1/3 = 1.33 PR(C) = .5 PR(D) = 1/2 + 1/3 = .83 2 links to D

  11. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.33/2 + .5/3 + .83/2 = 1.24

  12. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.33/2 + .5/3 + .83/2 = 1.24 PR(B) = 1.33 + .5/3 = 1.49

  13. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.33/2 + .5/3 + .83/2 = 1.24 PR(B) = 1.33 + .5/3 = 1.49 PR(C) = .83 / 2 = .415

  14. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.33/2 + .5/3 + .83/2 = 1.24 PR(B) = 1.33 + .5/3 = 1.49 PR(C) = .83 / 2 = .415 PR(D) = 1.33/2 + .5/3 = .83

  15. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.24, PR(B) = 1.49, PR(C) = .415, PR(D) = .83 Round 3 PR(A) = 1.49/2 + .415/3 + .83/2 = 1.30 PR(B) = 1.24 + .415/3 = 1.37 PR(C) = .83/2 = .415 PR(D) = 1.49/2 + .415/3 = .883

  16. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.24, PR(B) = 1.49, PR(C) = .415, PR(D) = .83 Round 3 PR(A) = 1.30, PR(B) =1.37, PR(C) =.415, PR(D) =.883 Round(4) PR(A) = 1.37/2 + .415/3 + .883/2 = 1.27 PR(B) = 1.30 + .415/3 = 1.43 PR(C) = .883/2 = .441 PR(D) = 1.37/2 + .415/3 = .823

  17. Page Rank Example A B C D A 0 1 0 0 B 1 0 0 1 C 1 1 0 1 D 1 0 1 0 Round 1 PR(A) = 1.33, PR(B) = 1.33, PR(C) = .5, PR(D) = .83 Round 2 PR(A) = 1.24, PR(B) = 1.49, PR(C) = .415, PR(D) = .83 Round 3 PR(A) = 1.30, PR(B) =1.37, PR(C) =.415, PR(D) =.883 Round(4) PR(A) = 1.27, PR(B) = 1.43, PR(C) = .441, PR(D) = .823 Document(A) is good because lots of documents link to it Document(B) is good because A only links to it, and lots of people link to A (it's an authority) Document(C) is bad, because few people link to it , and it links to everyone Document(D) is ok

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