Space complexity of perfect matching in bounded genus bipartite graphs

  • Authors:
  • Samir Datta;Raghav Kulkarni;Raghunath Tewari;N. V. Vinodchandran

  • Affiliations:
  • Chennai Mathematical Institute, Chennai, India;University of Chicago, Chicago, IL, USA;Indian Institute of Technology Kharagpur, Kharagpur, India;University of Nebraska - Lincoln, Lincoln, NE, USA

  • Venue:
  • Journal of Computer and System Sciences
  • Year:
  • 2012

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Abstract

We investigate the space complexity of certain perfect matching problems over bipartite graphs embedded on surfaces of constant genus (orientable or non-orientable). We show that the problems of deciding whether such graphs have (1) a perfect matching or not and (2) a unique perfect matching or not, are in the log-space complexity class Stoic Probabilistic Log-space (SPL). Since SPL is contained in the log-space counting classes @?L (in fact in Mod"kL for all k=2), C"=L, and PL, our upper bound places the above-mentioned matching problems in these counting classes as well. We also show that the search version, computing a perfect matching, for this class of graphs can be performed by a log-space transducer with an SPL oracle. Our results extend the same upper bounds for these problems over bipartite planar graphs known earlier. As our main technical result, we design a log-space computable and polynomially bounded weight function which isolates a minimum weight perfect matching in bipartite graphs embedded on surfaces of constant genus. We use results from algebraic topology for proving the correctness of the weight function.