Discrete & Computational Geometry

, Volume 45, Issue 1, pp 181–220 | Cite as

A Baby Steps/Giant Steps Probabilistic Algorithm for Computing Roadmaps in Smooth Bounded Real Hypersurface



We consider the problem of constructing roadmaps of real algebraic sets. This problem was introduced by Canny to answer connectivity questions and solve motion planning problems. Given s polynomial equations with rational coefficients, of degree D in n variables, Canny’s algorithm has a Monte Carlo cost of \(s^{n}\log(s)D^{O(n^{2})}\) operations in ℚ; a deterministic version runs in time \(s^{n}\log(s)D^{O(n^{4})}\) . A subsequent improvement was due to Basu, Pollack, and Roy, with an algorithm of deterministic cost \(s^{d+1}D^{O(n^{2})}\) for the more general problem of computing roadmaps of a semi-algebraic set (dn is the dimension of an associated object).

We give a probabilistic algorithm of complexity \((nD)^{O(n^{1.5})}\) for the problem of computing a roadmap of a closed and bounded hypersurface V of degree D in n variables, with a finite number of singular points. Even under these extra assumptions, no previous algorithm featured a cost better than \(D^{O(n^{2})}\) .


Computational real algebraic geometry Algorithms Roadmaps Complexity 


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© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.SALSA Project, CNRS, UMR 7606, LIP6, Case 169UPMC, Univ Paris 06, INRIA, Paris-Rocquencourt CenterParisFrance
  2. 2.Computer Science Department, Room 415, Middlesex CollegeThe University of Western OntarioLondonCanada

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