Fast spectral learning using Lanczos eigenspace projections

  • Authors:
  • Sridhar Mahadevan

  • Affiliations:
  • Department of Computer Science, University of Massachusetts, Amherst, MA

  • Venue:
  • AAAI'08 Proceedings of the 23rd national conference on Artificial intelligence - Volume 3
  • Year:
  • 2008

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Abstract

The core computational step in spectral learning - finding the projection of a function onto the eigenspace of a symmetric operator, such as a graph Laplacian - generally incurs a cubic computational complexity O(N3). This paper describes the use of Lanczos eigenspace projections for accelerating spectral projections, which reduces the complexity to O(nTop + n2N) operations, where n is the number of distinct eigenvalues, and Top is the complexity of mUltiplying T by a vector. This approach is based on diagonalizing the restriction of the operator to the Krylov space spanned by the operator and a projected function. Even further savings can be accrued by constructing an approximate Lanczos tridiagonal representation of the Krylov-space restricted operator. A key novelty of this paper is the use of Krylov-subspace modulated Lanczos acceleration for multi-resolution wavelet analysis. A challenging problem of learning to control a robot arm is used to test the proposed approach.