Learnability and Automatizability

  • Authors:
  • Misha Alekhnovich;Mark Braverman;Vitaly Feldman;Adam R. Klivans;Toniann Pitassi

  • Affiliations:
  • Institute for Advanced Studies;University of Toronto;Harvard University;Toyota Technological Institute;Institute for Advanced Studies and University of Toronto

  • Venue:
  • FOCS '04 Proceedings of the 45th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2004

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Abstract

We consider the complexity of properly learning concept classes, i.e. when the learner must output a hypothesis of the same form as the unknown concept. We present the following new upper and lower bounds on well-known concept classes: We show that unless NP = RP, there is no polynomial-time PA Clearning algorithm for DNF formulae where the hypothesis is an OR-of-thresholds. Note that as special cases, we show that neither DNF nor OR-of-thresholds are properly learnable unless NP = RP. Previous hardness results have required strong restrictions on the size of the output DNF formula. We also prove that it is NP-hard to learn the intersection of \ell\geqslant 2 halfspaces by the intersection of k halfspaces for any constant k 驴 0. Previous work held for the case when k = \ell. Assuming that NP 驴 DTIME(2^{n^\varepsilon} ) for a certain constant 驴