The thesis presentation discusses the challenges of providing online movie recommendations at scale using matrix factorization, highlighting that 75% of daily movie starts come from recommendations. It outlines the performance of a system tested on 1 million items and emphasizes the need for balanced clusters and efficient data handling. The document concludes with a summary of setup and performance metrics, indicating a successful implementation with 74% effectiveness.

1. Thesis presentation:
Online recommendations
at scale with matrix factorisation.
Royal Institute of Technology, Stockholm, Sweden 22 June 2012
Instituto Superior Técnico, Lisbon, Portugal Marcus Ljungblad
Universitat Politécnica de Catalunya, Barcelona, Spain marcus@ljungblad.nu

5. " 75% of the 30 million daily movie
starts are sourced from
recommendations.

6. " a key differentiating factor

7. 3 challenges

14. How do you serve
recommendations
from millions of
items to millions
of users online?

15. Video ratings
2 4 4 ? 1
3 5 ? ? 1
Users
? 4 2 1 ?
1 ? 1 3 3

16. f( )

17. Video ratings
2.05 3.97 3.96 2.12 1.01
2.93 5.02 3.21 1.61 0.98
Users
2.15 3.95 2.01 1.05 1.10
1.00 4.29 1.01 2.96 2.98

18. Video ratings
2.05 3.97 3.96 2.12 1.01 2 4 4 ? 1
Users
2.93 5.02 3.21 1.61 0.98 3 5 ? ? 1
2.15 3.95 2.01 1.05 1.10 ? 4 2 1 ?
1.00 4.29 1.01 2.96 2.98 1 ? 1 3 3

19. 2.05 3.97 3.96 2.12 1.01
2.93 5.02 3.21 1.61 0.98
2.15 3.95 2.01 1.05 1.10
1.00 4.29 1.01 2.96 2.98

20. 13x40
MILLION
RATINGS

29. Interface Delegate Router Worker
request
start
route
compute
top-N
merge
to json
reply

30. Interface Delegate Router Worker
request
start
route
compute
top-N
merge
to json
reply

31. Did it work?

32. Setup:
• 1-3 machines
• 1 million items
• same rack = high-speed
• 1 test machine

33. Performance!

34. Performance!
h uh?!

35. Did it work?
w ell

36. 74% = 74%
Offline Online

38. Summary:
... clustering depends on data ...
... need balanced clusters ...
... memory bound ...
... scales ok ...

39. Thank you!

41. Photos and pictures borrowed from the Internetz:
Iron Maiden cover: http://en.wikipedia.org/wiki/File:Iron_Maiden_(album)_cover.jpg
Cat picture: http://www.lastfm.es/group/Cats
Coins: http://www.sxc.hu/photo/1235540
iPhones: http://blog.bayuamus.com/2011/08/user-experience-comparison-between-htc-salsa-and-samsung-galaxy-mini/
Amazon recommendations: http://mashable.com/2010/08/06/online-retail-facebook-data/
TV remote: http://www.flickr.com/photos/62337512@N00/2749561795/sizes/z/in/photostream/
Headphones: http://www.flickr.com/photos/markusschoepke/82957375/sizes/m/in/photostream/
Function: http://en.wikipedia.org/wiki/File:Graph_of_example_function.svg
Home servers: http://www.flickr.com/photos/fabrico/477844434/sizes/z/in/photostream/

42. Extra material...

45. AXYDBLSZQ (1/2) / 1
AXYDBLSZQ (1/1) / 1
AXYDBLSZQ (1/1 + 2/3) / 2