Special Section on the Forty-Ninth Annual ACM Symposium on the Theory of Computing (STOC 2017)

This issue of SICOMP contains ten specially selected papers from STOC 2017, the Forty-ninth Annual ACM Symposium on the Theory of Computing, which was held June 19--23 in Montreal, Canada. The papers here were chosen to represent the range and quality of the STOC program. These papers have been revised and extended by their authors and subjected to the standard thorough reviewing process of SICOMP. The program committee for STOC 2017 consisted of Nina Balcan, Allan Borodin, Keren Censor-Hillel, Edith Cohen, Artur Czumaj, Yevgeniy Dodis, Andrew Drucker, Nick Harvey, Monika Henzinger, Russell Impagliazzo, Ken-ichi Kawarabayashi, Ravi Kumar, James R. Lee, Katrina Ligett, Aleksander Mądry, Cristopher Moore, Jelani Nelson, Eric Price, Amit Sahai, Jared Saia, Shubhangi Saraf, Alexander Sherstov, Mohit Singh, and Gábor Tardos. The program chair was Valerie King. Included in this issue are the following papers: ``Short Presburger Arithmetic Is Hard," by Danny Nguyen and Igor Pak, proves that the satisfiability of short sentences in Presburger arithmetic with $m+2$ alternating quantifiers is $\Sigma^{{P}}_m$-complete or $\Pi^{{P}}_m$-complete when the first quantifier is $\exists$ or $\forall$, respectively. ``An Efficient Reduction from Two-Source to Nonmalleable Extractors: Achieving Near-Logarithmic Min-Entropy," by Avraham Ben-Aroya, Dean Doron, and Amnon Ta-Shma, gets an explicit bipartite Ramsey graph (or a twosource extractor) for sets of size 2$k$ for $k = O(\log n \log \log n)$, using the currently best explicit nonmalleable extractors. ``Holographic Algorithm with Matchgates Is Universal for Planar \#CSP over Boolean Domain," by Jin-Yi Cai and Zhiguo Fu, classifies all counting CSPs over Boolean variables into one of three categories: polynomial-time tractable, \#P-hard for general instances but solvable in polynomial time over planar graphs, and \#P-hard over planar graphs. ``Deciding Parity Games in Quasipolynomial Time," by Cristian S. Calude, Sanjay Jain, Bakhadyr Khoussainov, Wei Li, and Frank Stephan, shows the parameterized parity game, with $n$ nodes and $m$ priorities, is in the class of fixed parameter tractable problems when parameterized over $m$. ``New Hardness Results for Routing on Disjoint Paths," by Julia Chuzhoy, David H. K. Kim, and Rachit Nimavat, proves that node-disjoint paths is $2^{\Omega(\sqrt{\log n})}$-hard to approximate, unless all problems in NP have algorithms with running time $n^{O(\log n)}$. ``A Weighted Linear Matroid Parity Algorithm," by Satoru Iwata and Yusuke Kobayashi, presents a combinatorial, deterministic, strongly polynomial-time algorithm for the weighted linear matroid parity problem. ``Targeted Pseudorandom Generators, Simulation Advice Generators, and Derandomizing Logspace," by William M. Hoza and Chris Umans, shows that $\mathbf{BPL} \subseteq \bigcap_{\alpha > 0} {DSPACE}(\log^{1 + \alpha} n)$, assuming that for every derandomization result for log-space algorithms there is a pseudorandom generator strong enough to nearly recover the derandomization by iterating over all seeds and taking a majority vote. ``Approximating Rectangles by Juntas and Weakly Exponential Lower Bounds for LP Relaxations of CSPs," by Pravesh K. Kothari, Raghu Meka, and Prasad Raghavendra, shows that for CSPs, subexponential size LP relaxations are as powerful as $n^{\Omega(1)}$-rounds of the Sherali--Adams LP hierarchy. ``Equivocating Yao: Constant-Round Adaptively Secure Multiparty Computation in the Plain Model," by Ran Canetti, Oxana Poburinnaya, and Muthuramakrishnan Venkitasubramaniam, defines a new type of encryption and shows that Yao's garbling scheme, implemented with this encryption mechanism, is secure against adaptive adversaries. ``Geodesic Walks in Polytopes," by Yin Tat Lee and Santosh Vempala, introduces the geodesic walk for sampling Riemannian manifolds and applies it to the problem of generating uniform random points from the interior of polytopes in ${\mathbb{R}}^{n}$ specified by m inequalities; the resulting sampling algorithm for polytopes mixes in $O^{*}(mn^{\frac{3}{4}})$ steps. We thank the authors, the STOC 2017 program committee, the STOC 2017 external reviewers, and the SICOMP referees for all of their hard work. Andy Drucker, Ravi Kumar, Amit Sahai, Mohit Singh, Guest editors

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