# A nearly optimal algorithm for deciding connectivity queries in smooth and bounded real algebraic sets

1 PolSys - Polynomial Systems
LIP6 - Laboratoire d'Informatique de Paris 6, Inria de Paris
Abstract : A roadmap for a semi-algebraic set $S$ is a curve which has a non-empty and connected intersection with all connected components of $S$. Hence, this kind of object, introduced by Canny, can be used to answer connectivity queries (with applications, for instance, to motion planning) but has also become of central importance in effective real algebraic geometry, since it is used in higher-level algorithms. In this paper, we provide a probabilistic algorithm which computes roadmaps for smooth and bounded real algebraic sets. Its output size and running time are polynomial in $(nD)^{n\log(d)}$, where $D$ is the maximum of the degrees of the input polynomials, $d$ is the dimension of the set under consideration and $n$ is the number of variables. More precisely, the running time of the algorithm is essentially subquadratic in the output size. Even under our assumptions, it is the first roadmap algorithm with output size and running time polynomial in $(nD)^{n\log(d)}$.
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Journal articles

https://hal.inria.fr/hal-00849057
Contributor : Mohab Safey El Din <>
Submitted on : Thursday, October 27, 2016 - 12:02:52 PM
Last modification on : Friday, May 24, 2019 - 5:26:57 PM
Long-term archiving on : Friday, February 3, 2017 - 12:35:56 PM

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Mohab Safey El Din, Éric Schost. A nearly optimal algorithm for deciding connectivity queries in smooth and bounded real algebraic sets. Journal of the ACM (JACM), Association for Computing Machinery, 2017, 63 (6), pp.48:1--48:37. ⟨10.1145/2996450⟩. ⟨hal-00849057v3⟩

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