English

Super Strong ETH is False for Random $k$-SAT

Data Structures and Algorithms 2018-10-16 v1 Computational Complexity

Abstract

It has been hypothesized that kk-SAT is hard to solve for randomly chosen instances near the "critical threshold", where the clause-to-variable ratio is 2kln2θ(1)2^k \ln 2-\theta(1). Feige's hypothesis for kk-SAT says that for all sufficiently large clause-to-variable ratios, random kk-SAT cannot be refuted in polynomial time. It has also been hypothesized that the worst-case kk-SAT problem cannot be solved in 2n(1ωk(1)/k)2^{n(1-\omega_k(1)/k)} time, as multiple known algorithmic paradigms (backtracking, local search and the polynomial method) only yield an 2n(11/O(k))2^{n(1-1/O(k))} time algorithm. This hypothesis has been called the "Super-Strong ETH", modeled after the ETH and the Strong ETH. Our main result is a randomized algorithm which refutes the Super-Strong ETH for the case of random kk-SAT, for any clause-to-variable ratio. Given any random kk-SAT instance FF with nn variables and mm clauses, our algorithm decides satisfiability for FF in 2n(1Ω(logk)/k)2^{n(1-\Omega(\log k)/k)} time, with high probability. It turns out that a well-known algorithm from the literature on SAT algorithms does the job: the PPZ algorithm of Paturi, Pudlak, and Zane (1998).

Keywords

Cite

@article{arxiv.1810.06081,
  title  = {Super Strong ETH is False for Random $k$-SAT},
  author = {Nikhil Vyas},
  journal= {arXiv preprint arXiv:1810.06081},
  year   = {2018}
}

Comments

15 pages

R2 v1 2026-06-23T04:39:08.402Z