Finding the Rare Cube

  • Authors:
  • Shlomo Hoory;Oded Margalit

  • Affiliations:
  • IBM Haifa Research Labs,;IBM Haifa Research Labs,

  • Venue:
  • ALT '08 Proceedings of the 19th international conference on Algorithmic Learning Theory
  • Year:
  • 2008

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Abstract

In this paper we investigate the problem of active learning the partition of the n-dimensional hypercube into mcubes, where the i-th cube has color i. The model we are using is exactlearning via color evaluation queries, without equivalence queries, as proposed by the work of Fine and Mansour. We give a randomized algorithm solving this problem in O(mlogn) expected number of queries, which is tight, while its expected running time is O(m2nlogn).Furthermore, we generalize the problem to allow partitions of the cube into mmonochromatic parts, where each part is the union of pcubes. We give two randomized algorithms for the generalized problem. The first uses O(mp22plogn) expected number of queries, which is almost tight with the lower bound. However, its naïve implementation requires an exponential running time in n. The second, more practical, algorithm achieves a better running time complexity of $\tilde{O}(m^2 n^2 2^{2^p})$. However, it may fail to learn the correct partition with an arbitrarily small probability and it requires slightly more expected number of queries: $\tilde{O}(mn 4^p)$, where the $\tilde{O}$ represents a poly logarithmic factor in m,n,2p.