decision trees protocols and the fourier entropy
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Decision trees, protocols, and the Fourier Entropy-Influence - PowerPoint PPT Presentation

Decision trees, protocols, and the Fourier Entropy-Influence Conjecture Andrew Wan (Simons Institute) John Wright (CMU) Chenggang Wu (Tsinghua) Fourier basics Given a Boolean function , Fourier


  1. Our results If is computable by a read-k DT , then . If is computable DT with expected depth d , and satisfies , then . also proven by [CKLS13] The FEI + conjecture of [OT13] composes. also proven by [OT13]

  2. Our technique • Want to show for certain Boolean functions .

  3. Our technique • Want to show for certain Boolean functions . • Previous papers have studied the expression

  4. Our technique • Want to show for certain Boolean functions . • Previous papers have studied the expression • We instead take an information theoretic approach via the Shannon Source Coding Theorem .

  5. Shannon Source Coding Theorem Given a random variable , avg # of bits needed to communicate .

  6. Shannon Source Coding Theorem Given a random variable , avg # of bits needed to communicate . Thus, to show , we need to construct an efficient protocol for communicating the value of .

  7. Shannon Source Coding Theorem Given a random variable , avg # of bits needed to communicate . Thus, to show , we need to construct an efficient protocol for communicating the value of . ( efficient = bits on average)

  8. a protocol for read-k DTs

  9. Protocol for read-k DTs is computed by 0 0 1 1 0 1 0 1 0 1

  10. Protocol for read-k DTs is computed by (a read-2 DT) 0 0 1 1 0 1 0 1 0 1

  11. Protocol for read-k DTs is computed by 0 0 1 1 0 1 0 1 0 1

  12. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1

  13. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  14. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  15. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  16. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  17. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  18. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  19. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  20. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  21. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  22. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  23. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  24. Protocol for read-k DTs is computed by Key fact : if is in the support 0 of , then the coordinates of appear in a root-to-leaf path in 0 1 1 . 0 1 0 1 0 1 Some sets in the support of :

  25. Protocol for read-k DTs Given , what should our protocol output? 0 0 1 1 0 1 0 1 0 1

  26. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 0 1 1 0 1 0 1 0 1

  27. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 0 1 0 1 0 1

  28. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 0 1 0 1 0 1

  29. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 0 1 0 1 0 1

  30. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 0 1 0 1 0 1

  31. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 3.) indicate which nodes fall in : 0 1 0 1 0 1

  32. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 3.) indicate which nodes fall in : 0 1 0 1 0 1

  33. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 3.) indicate which nodes fall in : 0 1 0 1 0 1

  34. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 2.) output the path’s description : 3.) indicate which nodes fall in : 0 1 0 1 0 1 4.) final output:

  35. Protocol for read-k DTs Given , what should our protocol output? 0 0 1 1 0 1 0 1 0 1

  36. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 0 1 1 0 1 0 1 0 1

  37. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 0 1 0 1 0 1

  38. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 lots of choices! 0 1 0 1 0 1

  39. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 lots of choices! 0 1 0 1 0 1

  40. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 lots of choices! 0 1 0 1 0 1

  41. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find a path containing 0 1 1 lots of choices! 0 1 0 1 0 1

  42. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find the shortest path 0 1 1 containing 0 1 0 1 0 1

  43. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find the shortest path 0 1 1 containing 0 1 0 1 0 1

  44. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find the shortest path 0 1 1 containing 2.) output the path’s description : 0 1 0 1 0 1

  45. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find the shortest path 0 1 1 containing 2.) output the path’s description : 0 1 0 1 0 1 3.) indicate which nodes fall in :

  46. Protocol for read-k DTs Given , what should our protocol output? e.g., 0 1.) find the shortest path 0 1 1 containing 2.) output the path’s description : 0 1 0 1 0 1 3.) indicate which nodes fall in : 4.) final output:

  47. Analysis of protocol • A decision tree should be arranged with the most influential variables near the top.

  48. Analysis of protocol • A decision tree should be arranged with the most influential variables near the top. • Since every path output is root-to-leaf, the variables near the top will contribute a lot of bits to the expectation.

  49. Analysis of protocol • A decision tree should be arranged with the most influential variables near the top. • Since every path output is root-to-leaf, the variables near the top will contribute a lot of bits to the expectation. • In summary, contributes a lot to the expectation ⇒ is near the top of the tree ⇒ is highly influential

  50. A bad tree Let be a decision tree.

  51. A bad tree Let be a decision tree.

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