27 Search Results for "Jansen, Thomas"

Document
DOI: 10.4230/DagRep.12.9.220
Transparent Quantitative Research as a User Interface Problem (Dagstuhl Seminar 22392)

Authors: Chat Wacharamanotham, Yvonne Jansen, Amelia A. McNamara, Kasper Hornbæk, Judy Robertson, and Lahari Goswami

Published in: Dagstuhl Reports, Volume 12, Issue 9 (2023)

Abstract
The replication crises in many scientific fields galvanize movements toward Open Science. Within this movement is a push for increasing research transparency. Although researchers in the areas of Human-Computer Interaction (HCI) and Visualization (VIS) face these challenges, they have methodological expertise to study, design, and evaluate innovations that could help improve research transparency. This Dagstuhl Seminar gathers HCI and VIS researchers and those from adjacent fields such as statistics and psychology to discuss challenges in promoting and adopting research transparency, create prototypes of potential solutions, and receive feedback from policy influencers in the research community. This seminar fostered seeds for future initiatives and collaboration toward improving research transparency in HCI, VIS, and other scientific fields.
Cite as

Chat Wacharamanotham, Yvonne Jansen, Amelia A. McNamara, Kasper Hornbæk, Judy Robertson, and Lahari Goswami. Transparent Quantitative Research as a User Interface Problem (Dagstuhl Seminar 22392). In Dagstuhl Reports, Volume 12, Issue 9, pp. 220-234, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Article{wacharamanotham_et_al:DagRep.12.9.220,
  author =	{Wacharamanotham, Chat and Jansen, Yvonne and McNamara, Amelia A. and Hornb{\ae}k, Kasper and Robertson, Judy and Goswami, Lahari},
  title =	{{Transparent Quantitative Research as a User Interface Problem (Dagstuhl Seminar 22392)}},
  pages =	{220--234},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2023},
  volume =	{12},
  number =	{9},
  editor =	{Wacharamanotham, Chat and Jansen, Yvonne and McNamara, Amelia A. and Hornb{\ae}k, Kasper and Robertson, Judy and Goswami, Lahari},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.12.9.220},
  URN =		{urn:nbn:de:0030-drops-178149},
  doi =		{10.4230/DagRep.12.9.220},
  annote =	{Keywords: Open Science, Research Transparency, Replicability, Reproducibility, Dagstuhl Seminar}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2017.10
A Lottery Model for Center-Type Problems with Outliers

Authors: David G. Harris, Thomas Pensyl, Aravind Srinivasan, and Khoa Trinh

Published in: LIPIcs, Volume 81, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)

Abstract
In this paper, we give tight approximation algorithms for the k-center and matroid center problems with outliers. Unfairness arises naturally in this setting: certain clients could always be considered as outliers. To address this issue, we introduce a lottery model in which each client is allowed to submit a parameter indicating the lower-bound on the probability that it should be covered and we look for a random solution that satisfies all the given requests. Out techniques include a randomized rounding procedure to round a point inside a matroid intersection polytope to a basis plus at most one extra item such that all marginal probabilities are preserved and such that a certain linear function of the variables does not decrease in the process with probability one.
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David G. Harris, Thomas Pensyl, Aravind Srinivasan, and Khoa Trinh. A Lottery Model for Center-Type Problems with Outliers. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 81, pp. 10:1-10:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{harris_et_al:LIPIcs.APPROX-RANDOM.2017.10,
  author =	{Harris, David G. and Pensyl, Thomas and Srinivasan, Aravind and Trinh, Khoa},
  title =	{{A Lottery Model for Center-Type Problems with Outliers}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)},
  pages =	{10:1--10:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-044-6},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{81},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} D. P. and Williamson, David P. and Vempala, Santosh S.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2017.10},
  URN =		{urn:nbn:de:0030-drops-75596},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2017.10},
  annote =	{Keywords: approximation algorithms, randomized rounding, clustering problems}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2017.16
Submodular Secretary Problems: Cardinality, Matching, and Linear Constraints

Authors: Thomas Kesselheim and Andreas Tönnis

Published in: LIPIcs, Volume 81, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)

Abstract
We study various generalizations of the secretary problem with submodular objective functions. Generally, a set of requests is revealed step-by-step to an algorithm in random order. For each request, one option has to be selected so as to maximize a monotone submodular function while ensuring feasibility. For our results, we assume that we are given an offline algorithm computing an alpha-approximation for the respective problem. This way, we separate computational limitations from the ones due to the online nature. When only focusing on the online aspect, we can assume alpha = 1. In the submodular secretary problem, feasibility constraints are cardinality constraints, or equivalently, sets are feasible if and only if they are independent sets of a k-uniform matroid. That is, out of a randomly ordered stream of entities, one has to select a subset of size k. For this problem, we present a 0.31alpha-competitive algorithm for all k, which asymptotically reaches competitive ratio alpha/e for large k. In submodular secretary matching, one side of a bipartite graph is revealed online. Upon arrival, each node has to be matched permanently to an offline node or discarded irrevocably. We give a 0.207alpha-competitive algorithm. This also covers the problem, in which sets of entities are feasible if and only if they are independent with respect to a transversal matroid. In both cases, we improve over previously best known competitive ratios, using a generalization of the algorithm for the classic secretary problem. Furthermore, we give an O(alpha d^(-2/(B-1)))-competitive algorithm for submodular function maximization subject to linear packing constraints. Here, d is the column sparsity, that is the maximal number of none-zero entries in a column of the constraint matrix, and B is the minimal capacity of the constraints. Notably, this bound is independent of the total number of constraints. We improve the algorithm to be O(alpha d^(-1/(B-1)))-competitive if both d and B are known to the algorithm beforehand.
Cite as

Thomas Kesselheim and Andreas Tönnis. Submodular Secretary Problems: Cardinality, Matching, and Linear Constraints. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 81, pp. 16:1-16:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{kesselheim_et_al:LIPIcs.APPROX-RANDOM.2017.16,
  author =	{Kesselheim, Thomas and T\"{o}nnis, Andreas},
  title =	{{Submodular Secretary Problems: Cardinality, Matching, and Linear Constraints}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)},
  pages =	{16:1--16:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-044-6},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{81},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} D. P. and Williamson, David P. and Vempala, Santosh S.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2017.16},
  URN =		{urn:nbn:de:0030-drops-75657},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2017.16},
  annote =	{Keywords: Secretary Problem, Online Algorithms, Submodular Maximization}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2017.49
Communication Complexity of Statistical Distance

Authors: Thomas Watson

Published in: LIPIcs, Volume 81, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)

Abstract
We prove nearly matching upper and lower bounds on the randomized communication complexity of the following problem: Alice and Bob are each given a probability distribution over $n$ elements, and they wish to estimate within +-epsilon the statistical (total variation) distance between their distributions. For some range of parameters, there is up to a log(n) factor gap between the upper and lower bounds, and we identify a barrier to using information complexity techniques to improve the lower bound in this case. We also prove a side result that we discovered along the way: the randomized communication complexity of n-bit Majority composed with n-bit Greater-Than is Theta(n log n).
Cite as

Thomas Watson. Communication Complexity of Statistical Distance. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 81, pp. 49:1-49:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{watson:LIPIcs.APPROX-RANDOM.2017.49,
  author =	{Watson, Thomas},
  title =	{{Communication Complexity of Statistical Distance}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2017)},
  pages =	{49:1--49:10},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-044-6},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{81},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} D. P. and Williamson, David P. and Vempala, Santosh S.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2017.49},
  URN =		{urn:nbn:de:0030-drops-75984},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2017.49},
  annote =	{Keywords: Communication, complexity, statistical, distance}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2016.30
The Niceness of Unique Sink Orientations

Authors: Bernd Gärtner and Antonis Thomas

Published in: LIPIcs, Volume 60, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016)

Abstract
Random Edge is the most natural randomized pivot rule for the simplex algorithm. Considerable progress has been made recently towards fully understanding its behavior. Back in 2001, Welzl introduced the concepts of reachmaps and niceness of Unique Sink Orientations (USO), in an effort to better understand the behavior of Random Edge. In this paper, we initiate the systematic study of these concepts. We settle the questions that were asked by Welzl about the niceness of (acyclic) USO. Niceness implies natural upper bounds for Random Edge and we provide evidence that these are tight or almost tight in many interesting cases. Moreover, we show that Random Edge is polynomial on at least n^{Omega(2^n)} many (possibly cyclic) USO. As a bonus, we describe a derandomization of Random Edge which achieves the same asymptotic upper bounds with respect to niceness.
Cite as

Bernd Gärtner and Antonis Thomas. The Niceness of Unique Sink Orientations. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 60, pp. 30:1-30:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{gartner_et_al:LIPIcs.APPROX-RANDOM.2016.30,
  author =	{G\"{a}rtner, Bernd and Thomas, Antonis},
  title =	{{The Niceness of Unique Sink Orientations}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016)},
  pages =	{30:1--30:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-018-7},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{60},
  editor =	{Jansen, Klaus and Mathieu, Claire and Rolim, Jos\'{e} D. P. and Umans, Chris},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2016.30},
  URN =		{urn:nbn:de:0030-drops-66538},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2016.30},
  annote =	{Keywords: random edge, unique sink orientation, random walk, reachmap, niceness}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2016.34
Lower Bounds on Same-Set Inner Product in Correlated Spaces

Authors: Jan Hazla, Thomas Holenstein, and Elchanan Mossel

Published in: LIPIcs, Volume 60, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016)

Abstract
Let P be a probability distribution over a finite alphabet Omega^L with all L marginals equal. Let X^(1), ..., X^(L), where X^(j) = (X_1^(j), ..., X_n^(j)) be random vectors such that for every coordinate i in [n] the tuples (X_i^(1), ..., X_i^(L)) are i.i.d. according to P. The question we address is: does there exist a function c_P independent of n such that for every f: Omega^n -> [0, 1] with E[f(X^(1))] = m > 0 we have E[f(X^(1)) * ... * f(X^(n))] > c_P(m) > 0? We settle the question for L=2 and when L>2 and P has bounded correlation smaller than 1.
Cite as

Jan Hazla, Thomas Holenstein, and Elchanan Mossel. Lower Bounds on Same-Set Inner Product in Correlated Spaces. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 60, pp. 34:1-34:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{hazla_et_al:LIPIcs.APPROX-RANDOM.2016.34,
  author =	{Hazla, Jan and Holenstein, Thomas and Mossel, Elchanan},
  title =	{{Lower Bounds on Same-Set Inner Product in Correlated Spaces}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2016)},
  pages =	{34:1--34:11},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-018-7},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{60},
  editor =	{Jansen, Klaus and Mathieu, Claire and Rolim, Jos\'{e} D. P. and Umans, Chris},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2016.34},
  URN =		{urn:nbn:de:0030-drops-66571},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2016.34},
  annote =	{Keywords: same set hitting, product spaces, correlation, lower bounds}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2015.625
Weighted Polynomial Approximations: Limits for Learning and Pseudorandomness

Authors: Mark Bun and Thomas Steinke

Published in: LIPIcs, Volume 40, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2015)

Abstract
Low-degree polynomial approximations to the sign function underlie pseudorandom generators for halfspaces, as well as algorithms for agnostically learning halfspaces. We study the limits of these constructions by proving inapproximability results for the sign function. First, we investigate the derandomization of Chernoff-type concentration inequalities. Schmidt et al. (SIAM J. Discrete Math. 1995) showed that a tail bound of delta can be established for sums of Bernoulli random variables with only O(log(1/delta))-wise independence. We show that their results are tight up to constant factors. Secondly, the “polynomial regression” algorithm of Kalai et al. (SIAM J. Comput. 2008) shows that halfspaces can be efficiently learned with respect to log-concave distributions on R^n in the challenging agnostic learning model. The power of this algorithm relies on the fact that under log-concave distributions, halfspaces can be approximated arbitrarily well by low-degree polynomials. In contrast, we exhibit a large class of non-log-concave distributions under which polynomials of any degree cannot approximate the sign function to within arbitrarily low error.
Cite as

Mark Bun and Thomas Steinke. Weighted Polynomial Approximations: Limits for Learning and Pseudorandomness. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 40, pp. 625-644, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{bun_et_al:LIPIcs.APPROX-RANDOM.2015.625,
  author =	{Bun, Mark and Steinke, Thomas},
  title =	{{Weighted Polynomial Approximations: Limits for Learning and Pseudorandomness}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2015)},
  pages =	{625--644},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-89-7},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{40},
  editor =	{Garg, Naveen and Jansen, Klaus and Rao, Anup and Rolim, Jos\'{e} D. P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2015.625},
  URN =		{urn:nbn:de:0030-drops-53274},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2015.625},
  annote =	{Keywords: Polynomial Approximations, Pseudorandomness, Concentration, Learning Theory, Halfspaces}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2014.643
Sampling a Uniform Solution of a Quadratic Equation Modulo a Prime Power

Authors: Chandan Dubey and Thomas Holenstein

Published in: LIPIcs, Volume 28, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)

Abstract
Let p be a prime and k, t be positive integers. Given a quadratic equation Q(x1,x2,...,xn)=t mod p^k in n-variables; we present a polynomial time Las-Vegas algorithm that samples a uniformly random solution of the quadratic equation.
Cite as

Chandan Dubey and Thomas Holenstein. Sampling a Uniform Solution of a Quadratic Equation Modulo a Prime Power. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 28, pp. 643-653, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)

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@InProceedings{dubey_et_al:LIPIcs.APPROX-RANDOM.2014.643,
  author =	{Dubey, Chandan and Holenstein, Thomas},
  title =	{{Sampling a Uniform Solution of a Quadratic Equation Modulo a Prime Power}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)},
  pages =	{643--653},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-74-3},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{28},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} and Devanur, Nikhil R. and Moore, Cristopher},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2014.643},
  URN =		{urn:nbn:de:0030-drops-47289},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2014.643},
  annote =	{Keywords: Quadratic Forms, Lattices, Modular, p-adic}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2014.721
Communication Complexity of Set-Disjointness for All Probabilities

Authors: Mika Göös and Thomas Watson

Published in: LIPIcs, Volume 28, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)

Abstract
We study set-disjointness in a generalized model of randomized two-party communication where the probability of acceptance must be at least alpha(n) on yes-inputs and at most beta(n) on no-inputs, for some functions alpha(n)>beta(n). Our main result is a complete characterization of the private-coin communication complexity of set-disjointness for all functions alpha and beta, and a near-complete characterization for public-coin protocols. In particular, we obtain a simple proof of a theorem of Braverman and Moitra (STOC 2013), who studied the case where alpha=1/2+epsilon(n) and beta=1/2-epsilon(n). The following contributions play a crucial role in our characterization and are interesting in their own right. (1) We introduce two communication analogues of the classical complexity class that captures small bounded-error computations: we define a "restricted" class SBP (which lies between MA and AM) and an "unrestricted" class USBP. The distinction between them is analogous to the distinction between the well-known communication classes PP and UPP. (2) We show that the SBP communication complexity is precisely captured by the classical corruption lower bound method. This sharpens a theorem of Klauck (CCC 2003). (3) We use information complexity arguments to prove a linear lower bound on the USBP complexity of set-disjointness.
Cite as

Mika Göös and Thomas Watson. Communication Complexity of Set-Disjointness for All Probabilities. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 28, pp. 721-736, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)

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@InProceedings{goos_et_al:LIPIcs.APPROX-RANDOM.2014.721,
  author =	{G\"{o}\"{o}s, Mika and Watson, Thomas},
  title =	{{Communication Complexity of Set-Disjointness for All Probabilities}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)},
  pages =	{721--736},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-74-3},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{28},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} and Devanur, Nikhil R. and Moore, Cristopher},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2014.721},
  URN =		{urn:nbn:de:0030-drops-47342},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2014.721},
  annote =	{Keywords: Communication Complexity, Set-Disjointness, All Probabilities}
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2014.885
Pseudorandomness and Fourier Growth Bounds for Width-3 Branching Programs

Authors: Thomas Steinke, Salil Vadhan, and Andrew Wan

Published in: LIPIcs, Volume 28, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)

Abstract
We present an explicit pseudorandom generator for oblivious, read-once, width-3 branching programs, which can read their input bits in any order. The generator has seed length O~( log^3 n ). The previously best known seed length for this model is n^{1/2+o(1)} due to Impagliazzo, Meka, and Zuckerman (FOCS'12). Our work generalizes a recent result of Reingold, Steinke, and Vadhan (RANDOM'13) for permutation branching programs. The main technical novelty underlying our generator is a new bound on the Fourier growth of width-3, oblivious, read-once branching programs. Specifically, we show that for any f : {0,1}^n -> {0,1} computed by such a branching program, and k in [n], sum_{|s|=k} |hat{f}(s)| < n^2 * (O(\log n))^k, where f(x) = sum_s hat{f}(s) (-1)^<s,x> is the standard Fourier transform over Z_2^n. The base O(log n) of the Fourier growth is tight up to a factor of log log n.
Cite as

Thomas Steinke, Salil Vadhan, and Andrew Wan. Pseudorandomness and Fourier Growth Bounds for Width-3 Branching Programs. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 28, pp. 885-899, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)

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@InProceedings{steinke_et_al:LIPIcs.APPROX-RANDOM.2014.885,
  author =	{Steinke, Thomas and Vadhan, Salil and Wan, Andrew},
  title =	{{Pseudorandomness and Fourier Growth Bounds for Width-3 Branching Programs}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)},
  pages =	{885--899},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-74-3},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{28},
  editor =	{Jansen, Klaus and Rolim, Jos\'{e} and Devanur, Nikhil R. and Moore, Cristopher},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2014.885},
  URN =		{urn:nbn:de:0030-drops-47456},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2014.885},
  annote =	{Keywords: Pseudorandomness, Branching Programs, Discrete Fourier Analysis}
}
Document
DOI: 10.4230/LIPIcs.STACS.2012.441
Playing Mastermind With Constant-Size Memory

Authors: Benjamin Doerr and Carola Winzen

Published in: LIPIcs, Volume 14, 29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012)

Abstract
We analyze the classic board game of Mastermind with n holes and a constant number of colors. The classic result of Chvatal (Combinatorica 3 (1983), 325-329) states that the codebreaker can find the secret code with Theta(n / log n) questions. We show that this bound remains valid if the codebreaker may only store a constant number of guesses and answers. In addition to an intrinsic interest in this question, our result also disproves a conjecture of Droste, Jansen, and Wegener (Theory of Computing Systems 39 (2006), 525-544) on the memory-restricted black-box complexity of the OneMax function class.
Cite as

Benjamin Doerr and Carola Winzen. Playing Mastermind With Constant-Size Memory. In 29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012). Leibniz International Proceedings in Informatics (LIPIcs), Volume 14, pp. 441-452, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{doerr_et_al:LIPIcs.STACS.2012.441,
  author =	{Doerr, Benjamin and Winzen, Carola},
  title =	{{Playing Mastermind With Constant-Size Memory}},
  booktitle =	{29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012)},
  pages =	{441--452},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-35-4},
  ISSN =	{1868-8969},
  year =	{2012},
  volume =	{14},
  editor =	{D\"{u}rr, Christoph and Wilke, Thomas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2012.441},
  URN =		{urn:nbn:de:0030-drops-34112},
  doi =		{10.4230/LIPIcs.STACS.2012.441},
  annote =	{Keywords: Algorithms, Mastermind, black-box complexity, memory-restricted algorithms, query complexity}
}
Document
DOI: 10.4230/LIPIcs.STACS.2012.519
Stronger Lower Bounds and Randomness-Hardness Trade-Offs Using Associated Algebraic Complexity Classes

Authors: Maurice Jansen and Rahul Santhanam

Published in: LIPIcs, Volume 14, 29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012)

Abstract
We associate to each Boolean language complexity class C the algebraic class a.C consisting of families of polynomials {f_n} for which the evaluation problem over the integers is in C. We prove the following lower bound and randomness-to-hardness results: 1. If polynomial identity testing (PIT) is in NSUBEXP then a.NEXP does not have poly size constant-free arithmetic circuits. 2. a.NEXP^RP does not have poly size constant-free arithmetic circuits. 3. For every fixed k, a.MA does not have arithmetic circuits of size n^k. Items 1 and 2 strengthen two results due to (Kabanets and Impagliazzo, 2004). The third item improves a lower bound due to (Santhanam, 2009). We consider the special case low-PIT of identity testing for (constant-free) arithmetic circuits with low formal degree, and give improved hardness-to-randomness trade-offs that apply to this case. Combining our results for both directions of the hardness-randomness connection, we demonstrate a case where derandomization of PIT and proving lower bounds are equivalent. Namely, we show that low-PIT is in i.o-NTIME[2^{n^{o(1)}}]/n^{o(1)} if and only if there exists a family of multilinear polynomials in a.NE/lin that requires constant-free arithmetic circuits of super-polynomial size and formal degree.
Cite as

Maurice Jansen and Rahul Santhanam. Stronger Lower Bounds and Randomness-Hardness Trade-Offs Using Associated Algebraic Complexity Classes. In 29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012). Leibniz International Proceedings in Informatics (LIPIcs), Volume 14, pp. 519-530, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{jansen_et_al:LIPIcs.STACS.2012.519,
  author =	{Jansen, Maurice and Santhanam, Rahul},
  title =	{{Stronger Lower Bounds and Randomness-Hardness Trade-Offs Using Associated Algebraic Complexity Classes}},
  booktitle =	{29th International Symposium on Theoretical Aspects of Computer Science (STACS 2012)},
  pages =	{519--530},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-35-4},
  ISSN =	{1868-8969},
  year =	{2012},
  volume =	{14},
  editor =	{D\"{u}rr, Christoph and Wilke, Thomas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2012.519},
  URN =		{urn:nbn:de:0030-drops-34307},
  doi =		{10.4230/LIPIcs.STACS.2012.519},
  annote =	{Keywords: Computational Complexity, Circuit Lower Bounds, Polynomial Identity Testing, Derandomization}
}
Document
DOI: 10.4230/DagRep.1.4.100
Artificial Immune Systems (Dagstuhl Seminar 11172)

Authors: Emma Hart, Thomas Jansen, and Jon Timmis

Published in: Dagstuhl Reports, Volume 1, Issue 4 (2011)

Abstract
This report documents the program and the outcomes of the Dagstuhl Seminar 11172 ``Artificial Immune Systems''. The purpose of the seminar was to bring together researchers from the areas of immune-inspired computing, theoretical computer science, randomised search heuristics, engineering, swarm intelligence and computational immunology in a highly interdisciplinary seminar to discuss two main issues: first, how to best develop a more rigorous theoretical framework for algorithms inspired by the immune system and second, to discuss suitable application areas for immune-inspired systems and how best to exploit the properties of those algorithms.
Cite as

Emma Hart, Thomas Jansen, and Jon Timmis. Artificial Immune Systems (Dagstuhl Seminar 11172). In Dagstuhl Reports, Volume 1, Issue 4, pp. 100-111, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)

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@Article{hart_et_al:DagRep.1.4.100,
  author =	{Hart, Emma and Jansen, Thomas and Timmis, Jon},
  title =	{{Artificial Immune Systems (Dagstuhl Seminar 11172)}},
  pages =	{100--111},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2011},
  volume =	{1},
  number =	{4},
  editor =	{Hart, Emma and Jansen, Thomas and Timmis, Jon},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.1.4.100},
  URN =		{urn:nbn:de:0030-drops-32004},
  doi =		{10.4230/DagRep.1.4.100},
  annote =	{Keywords: Artificial Immune Systems, Randomised Search Heuristics}
}
Document
DOI: 10.4230/LIPIcs.STACS.2011.165
Cross-Composition: A New Technique for Kernelization Lower Bounds

Authors: Hans L. Bodlaender, Bart M. P. Jansen, and Stefan Kratsch

Published in: LIPIcs, Volume 9, 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)

Abstract
We introduce a new technique for proving kernelization lower bounds, called cross-composition. A classical problem L cross-composes into a parameterized problem $Q$ if an instance of Q with polynomially bounded parameter value can express the logical OR of a sequence of instances of L. Building on work by Bodlaender et al. (ICALP 2008) and using a result by Fortnow and Santhanam (STOC 2008) we show that if an NP-hard problem cross-composes into a parameterized problem Q then Q does not admit a polynomial kernel unless the polynomial hierarchy collapses. Our technique generalizes and strengthens the recent techniques of using OR-composition algorithms and of transferring the lower bounds via polynomial parameter transformations. We show its applicability by proving kernelization lower bounds for a number of important graphs problems with structural (non-standard) parameterizations, e.g., Chromatic Number, Clique, and Weighted Feedback Vertex Set do not admit polynomial kernels with respect to the vertex cover number of the input graphs unless the polynomial hierarchy collapses, contrasting the fact that these problems are trivially fixed-parameter tractable for this parameter. We have similar lower bounds for Feedback Vertex Set.
Cite as

Hans L. Bodlaender, Bart M. P. Jansen, and Stefan Kratsch. Cross-Composition: A New Technique for Kernelization Lower Bounds. In 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 9, pp. 165-176, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)

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@InProceedings{bodlaender_et_al:LIPIcs.STACS.2011.165,
  author =	{Bodlaender, Hans L. and Jansen, Bart M. P. and Kratsch, Stefan},
  title =	{{Cross-Composition: A New Technique for Kernelization Lower Bounds}},
  booktitle =	{28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)},
  pages =	{165--176},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-25-5},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{9},
  editor =	{Schwentick, Thomas and D\"{u}rr, Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2011.165},
  URN =		{urn:nbn:de:0030-drops-30082},
  doi =		{10.4230/LIPIcs.STACS.2011.165},
  annote =	{Keywords: kernelization, lower bounds, parameterized complexity}
}
Document
DOI: 10.4230/LIPIcs.STACS.2011.177
Vertex Cover Kernelization Revisited: Upper and Lower Bounds for a Refined Parameter

Authors: Bart M. P. Jansen and Hans L. Bodlaender

Published in: LIPIcs, Volume 9, 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)

Abstract
Kernelization is a concept that enables the formal mathematical analysis of data reduction through the framework of parameterized complexity. Intensive research into the Vertex Cover problem has shown that there is a preprocessing algorithm which given an instance (G,k) of Vertex Cover outputs an equivalent instance (G',k') in polynomial time with the guarantee that G' has at most 2k' vertices (and thus O((k')^2) edges) with k' <= k. Using the terminology of parameterized complexity we say that k-Vertex Cover has a kernel with 2k vertices. There is complexity-theoretic evidence that both 2k vertices and Theta(k^2) edges are optimal for the kernel size. In this paper we consider the Vertex Cover problem with a different parameter, the size fvs(G) of a minimum feedback vertex set for G. This refined parameter is structurally smaller than the parameter k associated to the vertex covering number VC(G) since fvs(G) <= VC(G) and the difference can be arbitrarily large. We give a kernel for Vertex Cover with a number of vertices that is cubic in fvs(G): an instance (G,X,k) of Vertex Cover, where X is a feedback vertex set for G, can be transformed in polynomial time into an equivalent instance (G',X',k') such that k' <= k, |X'| <= |X| and most importantly |V(G')| <= 2k and |V(G')| in O(|X'|^3). A similar result holds when the feedback vertex set X is not given along with the input. In sharp contrast we show that the Weighted Vertex Cover problem does not have polynomial kernel when parameterized by fvs(G) unless the polynomial hierarchy collapses to the third level (PH=Sigma_3^p). Our work is one of the first examples of research in kernelization using a non-standard parameter, and shows that this approach can yield interesting computational insights. To obtain our results we make extensive use of the combinatorial structure of independent sets in forests.
Cite as

Bart M. P. Jansen and Hans L. Bodlaender. Vertex Cover Kernelization Revisited: Upper and Lower Bounds for a Refined Parameter. In 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 9, pp. 177-188, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)

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@InProceedings{jansen_et_al:LIPIcs.STACS.2011.177,
  author =	{Jansen, Bart M. P. and Bodlaender, Hans L.},
  title =	{{Vertex Cover Kernelization Revisited: Upper and Lower Bounds for a Refined Parameter}},
  booktitle =	{28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)},
  pages =	{177--188},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-25-5},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{9},
  editor =	{Schwentick, Thomas and D\"{u}rr, Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2011.177},
  URN =		{urn:nbn:de:0030-drops-30097},
  doi =		{10.4230/LIPIcs.STACS.2011.177},
  annote =	{Keywords: kernelization, lower bounds, parameterized complexity}
}
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