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Nearly Tight Bounds for Robust Proper Learning of Halfspaces with a Margin Ilias Diakonikolas Daniel M. Kane Pasin Manurangsi UW Madison UC San Diego Google Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin


  1. Nearly Tight Bounds for Robust Proper Learning of Halfspaces with a Margin Ilias Diakonikolas Daniel M. Kane Pasin Manurangsi UW Madison UC San Diego Google Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  2. Agnostic Proper Learning of Halfspaces Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - + - - - + - - - + - Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  3. Agnostic Proper Learning of Halfspaces Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + - - - + - - - + - Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  4. Agnostic Proper Learning of Halfspaces Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  5. Agnostic Proper Learning of Halfspaces Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  6. Agnostic Proper Learning of Halfspaces w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  7. Agnostic Proper Learning of Halfspaces w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  8. Agnostic Proper Learning of Halfspaces w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT + Ξ΅ - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  9. Agnostic Proper Learning of Halfspaces w* Input + w + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT + Ξ΅ - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  10. Agnostic Proper Learning of Halfspaces w* Input + w + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT + Ξ΅ - + - OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  11. Agnostic Proper Learning of Halfspaces w* Input + w + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT + Ξ΅ - + - Bad news: [Arora et al.’97] Unless NP = RP, no poly-time 𝛽 -learner for all constants 𝛽 . OPT = Min classifjcation error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 0] [Guruswami-Raghavendra’ 06, Feldman et al.’06] Even weak learning is NP-hard. Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  12. Agnostic Proper Learning of Halfspaces with a Margin Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  13. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT 𝛿 = Min 𝛿 -margin error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  14. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT 𝛿 = Min 𝛿 -margin error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  15. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - 𝛿 𝛿 + Output A halfspace w with β€œsmall” classifjcation error - - - + - - - + - OPT 𝛿 = Min 𝛿 -margin error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  16. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - 𝛿 𝛿 + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT 𝛿 + Ξ΅ - + - OPT 𝛿 = Min 𝛿 -margin error among all halfspaces = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  17. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - 𝛿 𝛿 + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT 𝛿 + Ξ΅ - + - Margin Assumption OPT 𝛿 = Min 𝛿 -margin error among all halfspaces - β€œRobustness” of the optimal halfspace to β„“ 2 noise = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

  18. Agnostic Proper Learning of Halfspaces with a Margin w* Input + + - - + - Labeled samples (x 1 , y 1 ), (x 2 , y 2 ), … ∈ 𝓒 (d) Γ— {Β±1} + from distribution 𝓔 + - Positive real number Ξ΅ - 𝛿 𝛿 + Output A halfspace w with β€œsmall” classifjcation error - - - + - An algorithm is a 𝛽 -learner if it outputs w with - classifjcation error at most 𝛽 ・ OPT 𝛿 + Ξ΅ - + - Margin Assumption OPT 𝛿 = Min 𝛿 -margin error among all halfspaces - β€œRobustness” of the optimal halfspace to β„“ 2 noise = min w Pr (x, y)~ 𝓔 [<w, x> ・ y < 𝛿 ] - Variants used in Perceptron, SVMs Nearly Tight Bound for Robust Proper Learning of Halfspaces with a Margin Diakonikolas, Kane, Manurangsi

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