Paper Info
Title
Fine-grained reductions from approximate counting to decision.
Abstract
In this paper, we introduce a general framework for fine-grained reductions of approximate counting problems to their decision versions. (Thus we use an oracle that decides whether any witness exists to multiplicatively approximate the number of witnesses with minimal overhead.) This mirrors a foundational result of Sipser (STOC 1983) and Stockmeyer (SICOMP 1985) in the polynomial-time setting, and a similar result of Müller (IWPEC 2006) in the FPT setting. Using our framework, we obtain such reductions for some of the most important problems in fine-grained complexity: the Orthogonal Vectors problem, 3SUM, and the Negative-Weight Triangle problem (which is closely related to All-Pairs Shortest Path). While all these problems have simple algorithms over which it is conjectured that no polynomial improvement is possible, our reductions would remain interesting even if these conjectures were proved; they have only polylogarithmic overhead, and can therefore be applied to subpolynomial improvements such as the n3/exp(Θ(√logn))-time algorithm for the Negative-Weight Triangle problem due to Williams (STOC 2014). Our framework is also general enough to apply to versions of the problems for which more efficient algorithms are known. For example, the Orthogonal Vectors problem over GF(m)d for constant m can be solved in time n·poly(d) by a result of Williams and Yu (SODA 2014); our result implies that we can approximately count the number of orthogonal pairs with essentially the same running time. We also provide a fine-grained reduction from approximate #SAT to SAT. Suppose the Strong Exponential Time Hypothesis (SETH) is false, so that for some 1<c<2 and all k there is an O(cn)-time algorithm for #k-SAT. Then we prove that for all k, there is an O((c+o(1))n)-time algorithm for approximate #k-SAT. In particular, our result implies that the Exponential Time Hypothesis (ETH) is equivalent to the seemingly-weaker statement that there is no algorithm to approximate #3-SAT to within a factor of 1+ε in time 2o(n)/ε2 (taking ε > 0 as part of the input). A full version of this paper containing detailed proofs is available at https://arxiv.org/abs/1707.04609.
Year
DOI
Venue
2018
10.1145/3188745.3188920
STOC '18: Symposium on Theory of Computing Los Angeles CA USA June, 2018
Keywords
DocType
Volume
Approximate counting,fine-grained complexity,orthogonal vectors,satisfiability,isolation lemma
Conference
abs/1707.04609
ISSN
ISBN
Citations 
0737-8017
978-1-4503-5559-9
2
PageRank 
References 
Authors
0.41
20
2
Name
Order
Citations
PageRank
Holger Dell122016.74
John Lapinskas2134.25