Papers sorted chronologically

    Differential Privacy and Sublinear Time are Incompatible sometimes. Jeremiah Blocki, Hendrik Fichtenberger, Elena Grigorescu and Tamalika Mukherjee
    [full] 2024
    Directed Buy-at-Bulk Spanners. Elena Grigorescu, Nithish Kumar, Young-San Lin.
    [full] 2024
    On k-Mer-Based and Maximum Likelihood Estimation Algorithms for Trace Reconstruction. Kuan Cheng, Elena Grigorescu, Xin Li, Madhu Sudan, Minshen Zhu.
    ISIT 2024 (to appear) [full]
    On Computing Discretized Ricci Curvatures of Graphs Bhaskar DasGupta, Elena Grigorescu, Tamalika Mukherjee
    Theoretical Computer Science (to appear).
    Approximation Algorithms for Directed Weighted Spanners. Elena Grigorescu, Nithish Kumar, Young-San Lin.
    APPROX 2023 [full]
    How to Make your Approximation Algorithm Private. Jeremiah Blocki, Elena Grigorescu, Tamalika Mukherjee, Samson Zhou.
    RANDOM 2023 [full]
    On Relaxed Locally Decodable Codes for Hamming and Insertion-Deletion Errors, Alex Block, Jeremiah Blocki, Kuan Cheng, Elena Grigorescu, Xin Li, Yu Zheng, Minshen Zhu.
    Computational Complexity Conference (CCC) 2023 [ conference] [full]
    Learning-Augmented Algorithms for Online Linear and Semidefinite Programming Elena Grigorescu, Young-San Lin, Sandeep Silwal, Maoyuan Song, Samson Zhou
    NeuIPS 2022 (Spotlight presentation) [full]
    Hardness of Maximum Likelihood Learning of DPPs Elena Grigorescu, Brendan Juba, Karl Wimmer, Ning Xie
    COLT 2022 [full]
    Privately Estimating Graph Parameters in Sublinear Time Jeremiah Blocki, Elena Grigorescu, and Tamalika Mukherjee
    ICALP 2022 [full]
    Exponential Lower Bounds for Locally Decodable Codes Correcting Insertions and Deletions, Jeremiah Blocki, Kuan Cheng, Elena Grigorescu, Xin Li, Yu Zheng, Minshen Zhu.
    FOCS 2021. [full]
    Online Directed Spanners and Steiner Forests Elena Grigorescu, Young-San Lin, Kent Quanrud
    APPROX 2021 [full] (Theory of Computing (invited to Special Issue for APPROX21), 2023, to appear)
    Differentially Private Sublinear-Time Clustering Jeremiah Blocki, Elena Grigorescu, and Tamalika Mukherjee
    ISIT 2021 [conference], [full]
    Limitations of Mean-Based Algorithms for Trace Reconstruction at Small Distance Elena Grigorescu, Madhu Sudan, Minshen Zhu
    ISIT 2021 [full] IEEE Trans. Inf. Theory 2022.
    List Learning with Attribute Noise Mahdi Cheraghchi, Elena Grigorescu, Brendan Juba, Karl Wimmer, Ning Xie.
    AISTATS 2021 [full]
    Locally Decodable/Correctable Codes for Insertions and Deletions Alex Block, Jeremiah Blocki, Elena Grigorescu, Shubhang Kulkarni, Minshen Zhu
    FSTTCS 2020 [full]
    Fixed-Parameter Algorithms for Longest Heapable Subsequence and Maximum Binary Tree Kathik Chandrasekaran, Elena Grigorescu, Gabriel Istrate, Shubhang Kulkarni, Young-San Lin, Minshen Zhu. IPEC 2020 [conference] [full]
    The Maximum Binary Tree Problem Kathik Chandrasekaran, Elena Grigorescu, Gabriel Istrate, Shubhang Kulkarni, Young-San Lin, Minshen Zhu.
    ESA 2020.[full]. Algorithmica, 2021.
    Relaxed Locally Correctable Codes in Computationally Bounded Channels Jeremiah Blocki, Venkata Gandikota, Elena Grigorescu, Samson Zhou.
    Brief announcement in ICALP 2018. [brief]. Proceedings of ISIT 2019. [full]
    Structural Results on Matching Estimation with Applications to Streaming Marc Bury, Elena Grigorescu, Andrew McGregor, Morteza Monemizadeh, Chris Schwiegelshohn, Sofya Vorotnikova, Samson Zhou [pdf] (Joint journal version of this, this, and this.) Algorithmica, 2019.
    Nearly-Optimal Distinct Elements and Heavy Hitters in the Sliding Window Model Vladimir Braverman, Elena Grigorescu, Harry Lang, David Woodruff, Samson Zhou.
    Proceedings of APPROX 2018. [full]
    Flipping out with Many Flips: Hardness of Testing k-Monotonicity Elena Grigorescu, Akash Kumar, Karl Wimmer.
    Proceedings of RANDOM 2018. [pdf]
    Periodicity in Data Streams with Wildcards Funda Ergün, Elena Grigorescu, Erfan Sadeqi Azer, Samson Zhou.
    Proceedings of CSR, 2018 (to appear) [full]. Invited to special issue of Theory of Computing Systems.
    Lattice-Based Locality Sensitive Hashing is Optimal Karthik Chandrasekaran, Daniel Dadush, Venkata Gandikota, Elena Grigorescu
    Proceedings of Innovations in Theoretical Computer Science (ITCS), 2018. [conference]
    Communication-Efficient Distributed Learning of Discrete Distributions Ilias Diakonikolas, Elena Grigorescu, Jerry Li, Abhiram Natarajan, Krzysztof Onak, Ludwig Schmidt
    Proceedings of NIPS 2017. Oral presentation. [conference]
    Maximally Recoverable Codes: the Bounded Case Venkata Gandikota, Elena Grigorescu, Clayton Thomas, Minshen Zhu
    Proceedings of Allerton Conference on Communication, Control, and Computing, 2017. [pdf]
    Streaming Periodicity with Mismatches Funda Ergun, Elena Grigorescu, Erfan Sadeqi Azer, Samson Zhou.
    Proceedings of RANDOM 2017. [pdf]
    Streaming for Aibohphobes: Longest Palindrome with Mismatches Elena Grigorescu, Erfan Sadeqi Azer, Samson Zhou. [pdf]
    Proceedings of FSTTCS, 2017.
    Longest Alignment with Edits in Data Streams Elena Grigorescu, Erfan Sadeqi Azer, Samson Zhou. [pdf]
    Proceedings of Allerton Conference on Communication, Control, and Computing, 2017
    Testing k-Monotonicity (The Rise and Fall of Boolean Functions) Clément Canonne, Elena Grigorescu, Siyao Guo, Akash Kumar, Karl Wimmer.
    Accepted to Theory of Computing, 2017. Preliminary version in the Proceedings of Innovations in Theoretical Computer Science (ITCS), 2017. [pdf]
    Local Testing of Lattices Karthik Chandrasekaran, Mahdi Cheraghchi, Venkata Gandikota, Elena Grigorescu.
    SIDMA, 2018 (accepted). Preliminary version in Proceedings of FSTTCS 2016. [conference] [full]
    Nearly Optimal Sparse Group Testing Venkata Gandikota, Elena Grigorescu, Sidharth Jaggi, Samson Zhou.
    IEEE Transactions on Information Theory (accepted). Preliminary version in Proceedings of Allerton Conference on Communication, Control, and Computing, 2016. [conference] [full]
    NP-hardness of Reed-Solomon Decoding and the Prouhet-Tarry-Escott Problem Venkata Gandikota, Badih Ghazi, Elena Grigorescu.
    SICOMP 2018 (accepted). Preliminary in proceedings of FOCS 2016. [conference] [full]
    AC0-MOD2 Lower Bounds for the Boolean Inner-Product Mahdi Cheraghchi, Elena Grigorescu, Brendan Juba, Karl Wimmer, Ning Xie.
    Journal of Computer and System Sciences, 2018 (accepted). Preliminary version in Proceedings of ICALP 2016. [conference] [full]
    We show super-linear bounds for the problem of computing the Inner-Product function on AC0 circuits with parity gates just above the input level. These are the current state-of-the-art bounds on the problem.
    Deciding Orthogonality in Construction-A Lattices Karthik Chandrasekaran, Venkata Gandikota, Elena Grigorescu
    SIDMA, 2017. Preliminary version in Foundations of Software Technology and Theoretical Computer Science (FSTTCS) 2015. [pdf]
    On the NP-hardness of Bounded Distance Decoding of Reed-Solomon Codes Venkata Gandikota, Badih Ghazi, Elena Grigorescu
    IEEE International Symposium on Information Theory (ISIT) 2015. [conference] [full]
    Tight Lower Bounds for Testing Linear Isomorphism Elena Grigorescu, Karl Wimmer, Ning Xie.
    Proceedings of RANDOM 2013. [pdf]
    We show a tight adaptive, two-sided lower bound for testing linear isomorphism to the inner-product function. This is the first lower bound for testing linear isomorphism to a specific function that matches the trivial upper bound. We also show an exponential query lower bound for any adaptive, two-sided tester for membership in a large subclass of bent functions.
    A Lower-Variance Randomized Algorithm for Approximate String Matching Mikhail Atallah, Elena Grigorescu,Yi Wu.
    Information Processing Letters, 2013. [pdf]
    We provide an unbiased estimator for the score of matches between a text string and a pattern string, of smaller variance than in previous algorithms.
    Statistical Algorithms and a Lower Bound for Planted Clique Vitaly Feldman, Elena Grigorescu, Lev Reyzin, Santosh Vempala, Ying Xiao.
    J. ACM 2017. Preliminary version in Proceedings of STOC 2013. [conference] [full]
    We introduce a framework for proving lower bounds on computational problems over distributions, based on defining a restricted class of algorithms called statistical algorithms. For well-known problems over distributions, we give lower bounds on the complexity of any statistical algorithm. These include a nearly optimal lower bound for detecting planted bipartite clique distributions (or planted dense subgraph distributions) when the planted clique has small size.
    List Decoding Barnes-Wall Lattices Elena Grigorescu, Chris Peikert.
    Computational Complexity, 2017. Preliminary version in Proceedings of the Conference on Computational Complexity (CCC), 2012 [pdf]
    Motivated by the similar discrete linear structure of linear codes and point lattices, and their many shared applications, we initiate the study of list decoding for lattices. We focus on combinatorial and algorithmic questions related to list decoding for the well-studied family of Barnes-Wall lattices. Our results imply a polynomial-time list-decoding algorithm for any error radius bounded away from the minimum distance, thus beating a typical barrier for natural error-correcting codes posed by the Johnson radius.
    Testing Odd-Cycle Freeness in Boolean Functions Arnab Bhattacharyya, Elena Grigorescu, Prasad Raghavendra, Asaf Shapira.
    Combinatorics, Probability and Computing 21(6): 835-855, 2012. Proceedings of ACM-SIAM Symposium on Discrete Algorithms (SODA), 2012. [conference] [full]
    We continue the study of boolean linear-invariant properties defined over the hypercube and draw more connections to the testability of dense graphs. We show that an important family in this class (called `odd-cycle free') is efficiently testable. We also show that a canonical tester for this property only blows up the query complexity polynomially. These results suggest new open questions that attempt to cast light into the larger program of characterizing testable linear-invariant properties.
    Explicit Low-Weight Bases for BCH Codes Elena Grigorescu, Tali Kaufman.
    IEEE Transactions on Information Theory, 2011. [pdf]
    Motivated by applications in property testing, we investigate explicit low-weight codewords and bases of low-weight codewords for the well-studied BCH codes. We exhibit such codewords in some restricted settings.
    On Noise Tolerant Learning of Sparse Parities and Related Problems Elena Grigorescu, Lev Reyzin, Santosh Vempala.
    Proceedings of the International Conference on Algorithmic Learning Theory (ALT), 2011. [pdf]
    We propose an improved algorithm for learning sparse parities over arbitrary distributions.
    On Sums of Locally Testable Affine Invariant Properties Eli Ben-Sasson, Elena Grigorescu, Ghid Maatouk, Amir Shpilka, Madhu Sudan.
    Proceedings of the International Workshop on Randomization and Computation (RANDOM), 2011. [conference] [full]
    Linear codes (properties) that are also affine-invariant represent well-studied objects in the areas of local-testing, local-correcting, and local-decoding. An important open question in algebraic property testing is: what are neccessary and sufficient conditions that unify the testability of all these properties? The notion of `single-orbit' has been identified in the literature as a promising structural feature that leads to testability. This notion allows us in this work to broaden the class of known testable affine invariant properties by considering a basic, yet nontrivial operation on properties that have a single orbit, namely summation. Our results here together with previous results from the literature suggest the first conjecture that attempts to essentially capture the structure of all testable affine invariant properties.
    Steiner Transitive-Closure Spanners of Low-Dimensional Posets Peter Berman, Arnab Bhattacharyya, Elena Grigorescu, Sofya Raskhodnikova, David Woodruff, Grigory Yaroslavtsev.
    Combinatorica 34(3): 255-277 (2014). Preliminary version in Proceedings of the International Colloquium on Automata, Languages and Programming (ICALP), 2011. [conference] [full]
    Motivated by applications to property reconstruction and access control hierarchies, we concentrate on Steiner TC-spanners for partially ordered sets. We present a nearly tight lower bound on the size of Steiner 2-TC-spanners of d-dimensional directed hypergrids. It implies better lower bounds on the complexity of local reconstructors of monotone functions and functions with low Lipschitz constant. We also show a lower bound on the size of Steiner k-TC-spanners of d-dimensional posets that almost matches the known upper bounds.
    Separations of Matroid Freeness Properties Arnab Bhattacharyya, Elena Grigorescu, Jakob Nordström, Ning Xie.
    Technical Report TR10-136, Electronic Colloquium on Computational Complexity (ECCC), August 2010. [pdf]
    We focus again on boolean linear-invariant properties over the hypercube defined by forbidden patterns. We initiate a systematic study of these properties from the somewhat subtle point of view that different local characterizations by forbidden patterns can lead to properties that are essentially the same in a property testing sense. We identify a combinatorial tool (called `labelled matroid homomorphism') that captures the relationship between the constraints in a way relevant to the question of distinguishing the respective properties that they define.
    Symmetries in Algebraic Property Testing Elena Grigorescu
    PhD Thesis, MIT, 2010.
    A Unified Framework for Testing Linear-Invariant Properties Arnab Bhattacharyya, Elena Grigorescu, Asaf Shapira .
    Random Struct. Algorithms 46(2): 232-260 (2015). Preliminary version in Proceedings of the Symposium on Foundations of Computer Science (FOCS), 2010. [conference] [full]
    We propose a framework for analyzing the testability of boolean linear-invariant properties defined over the hypercube by drawing ideas from mysterious syntactic connections to the testability of graph properties, which is an area well-understood. Our results show the testability of a large class of linear-invariant properties, defined by forbidding a possibly infinite collection of arbitrary patterns. Based on these results we formulate the first conjecture that attempts to unify the testability of all boolean properties that are invariant under linear transformations and are testable with one sided error.
    Lower Bounds for Local Monotonicity Reconstructors from Transitive-Closure Spanners Arnab Bhattacharyya, Elena Grigorescu, Madhav Jha, Kyomin Jung, Sofya Raskhodnikova, David Woodruff.
    SIAM Journal on Discrete Mathematics 26(2): 618-646 (2012). Proceedings of the International Workshop on Randomization and Computation (RANDOM), 2010. [conference] [full]
    We continue the study of Transitive Closure Spanners and reveal a connection to `local monotonicity reconstructors', which are algorithms that reconstruct monotone functions from corrupted versions, in a distributed manner. This connection allows us to derive lower bounds on the query complexity of local monotonicity reconstructors from lower bounds on the size of TC-spanners. We study such lower bounds on directed hypercubes and hypergrids.
    A Local Decision Test for Sparse Polynomials Elena Grigorescu, Kyomin Jung, Ronitt Rubinfeld .
    Information Processing Letters, v.110, n.20, 898-901, 2010. [pdf]
    We show a local test for deciding if a polynomial is sparse or not.
    Error-Correcting Data Structures Victor Chen, Elena Grigorescu, Ronald de Wolf.
    SIAM Journal on Computing 42(1): 84-111 (2013). Proceedings of the Symposium on Theoretical Aspects of Computer Science (STACS), 2010. [conference] [full]
    We construct efficient data structures that are resilient against a constant fraction of adversarial noise. Our model requires that the decoder answers most queries correctly with high probability. In this work, we study two data structure problems: membership and polynomial evaluation. We show that these two problems have constructions that are simultaneously efficient and error-correcting.
    Succinct Representation of Codes with Applications to Testing Elena Grigorescu, Tali Kaufman, Madhu Sudan.
    SIAM Journal on Discrete Mathematics 26(4): 1618-1634 (2012). Proceedings of the International Workshop on Randomization and Computation (RANDOM), 2009. [conference] [full]
    We show that the dual of every ``sparse'' binary code whose symmetry group includes the group of non-singular affine transformations, has the single local orbit property (i.e., it is specified by a single local constraint and its translations under the affine group. ) This class includes the dual-BCH codes for whose duals (i.e., for BCH codes) simple bases were not known.
    Transitive-Closure Spanners Arnab Bhattacharyya , Elena Grigorescu, Kyomin Jung, Sofya Raskhodnikova, David Woodruff.
    SIAM Journal on Computing 41(6): 1380-1425 (2012). Proceedings of the ACM-SIAM Symposium on Discrete Algorithms (SODA), 2009. [conference] [full]
    We introduce the notion of Transitive-Closure spanners of a directed graph as a common abstraction to applications in data structures, monotonicity testing and access control. We present algorithms for approximating the size of the sparsest k-TC spanner, and prove strong hardness results for this problem. In addition, our structural bounds for path-separable (directed) graphs lead to improved monotonicity testers for these posets.
    2-Transitivity is Insufficient for Local Testability Elena Grigorescu, Tali Kaufman, Madhu Sudan.
    Journal of Computational Complexity 22(1): 137-158 (2013). Proceedings of the Conference on Computational Complexity (CCC), 2008. [conference] [full]
    In this work we refute a conjecture from the literature, stating that the presence of a single low weight codeword in the dual of a code, and ``2-transitivity'' of the code (i.e., the code is invariant under a 2-transitive group of permutations on the coordinates of the code) suffice to imply local testability.
    Decodability of Group Homomorphisms Beyound the Johnson Bound Irit Dinur, Elena Grigorescu, Swastik Kopparty, Madhu Sudan.
    Proceedings of the ACM Symposium on Theory of Computing (STOC), 2008. [conference] [full]
    We show that the code whose codewords are the homomorphisms between any two finite abelian groups is locally list decodable from a fraction of errors arbitrarily close to its minimum distance. The heart of the argument is a combinatorial result which gives an upper bound on the number of codewords in within a certain distance from any given word.
    Local Decoding and Testing for Homomorphisms Elena Grigorescu, Swastik Kopparty, Madhu Sudan.
    Proceedings of the International Workshop on Randomization and Computation (RANDOM), 2006. [conference] [full]
    We initiate a systematic study of local decoding of codes based on group homomorphisms. We present an efficient local list decoder for codes from any abelian group G to a fixed abelian group H. Our results give a new generalization of the classical work of Goldreich and Levin, and give a new abstraction of the list decoder of Sudan, Trevisan and Vadhan.
    The Insulation Sequence of a Graph Elena Grigorescu
    Discrete Applied Mathematics, Volume 134, Issues 1-3, 2004, 77-90. [pdf]
    We consider certain generalizations of independent sets, called insulated sets, and completely characterize the possible orderings of an insulated sequence of a graph.
    Decreasing the Diameter of Cycles Elena Grigorescu
    Journal of Graph Theory, Volume 43, Issues 4, 2003, 299-303. [pdf]
    We improve some lower bounds on the number of edges to be added to a cycle in order to decrease its diameter to 2 or 3.