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arXiv · 1411.7747

A Characterization of hard-to-cover CSPs

Amey Bhangale·Prahladh Harsha·Girish Varma
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Abstract

We continue the study of the covering complexity of constraint satisfaction problems (CSPs) initiated by Guruswami, H{\aa}stad and Sudan [SIAM J. Comp. 2002] and Dinur and Kol [CCC'13]. The covering number of a CSP instance $\Phi$ is the smallest number of assignments to the variables of $\Phi$, such that each constraint of $\Phi$ is satisfied by at least one of the assignments. We show the following results: 1. Assuming a covering variant of the Unique Games Conjecture, introduced by Dinur and Kol, we show that for every non-odd predicate $P$ over any constant-size alphabet and every integer $K$, it is NP-hard to approximate the covering number within a factor of $K$. This yields a complete characterization of CSPs over constant-size alphabets that are hard to cover. 2. For a large class of predicates that are contained in the 2k-LIN predicate, we show that it is quasi-NP-hard to distinguish between instances with covering number at most $2$ and those with covering number at least $\Omega(\log\log n)$. This generalizes and improves the 4-LIN covering hardness result of Dinur and Kol.

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Amey Bhangale, Prahladh Harsha, Girish Varma. 2014-11-28. A Characterization of hard-to-cover CSPs. https://doi.org/10.4086/toc.2020.v016a016%2C%2010.4230%2Flipics.ccc.2015.280

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