5 Search Results for "Xia, Li-Yao"

Document
DOI: 10.4230/LIPIcs.STACS.2023.44
An 𝒪(3.82^k) Time FPT Algorithm for Convex Flip Distance

Authors: Haohong Li and Ge Xia

Published in: LIPIcs, Volume 254, 40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023)

Abstract
Let P be a convex polygon in the plane, and let T be a triangulation of P. An edge e in T is called a diagonal if it is shared by two triangles in T. A flip of a diagonal e is the operation of removing e and adding the opposite diagonal of the resulting quadrilateral to obtain a new triangulation of P from T. The flip distance between two triangulations of P is the minimum number of flips needed to transform one triangulation into the other. The Convex Flip Distance problem asks if the flip distance between two given triangulations of P is at most k, for some given parameter k ∈ ℕ. We present an FPT algorithm for the Convex Flip Distance problem that runs in time 𝒪(3.82^k) and uses polynomial space, where k is the number of flips. This algorithm significantly improves the previous best FPT algorithms for the problem.
Cite as

Haohong Li and Ge Xia. An 𝒪(3.82^k) Time FPT Algorithm for Convex Flip Distance. In 40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 254, pp. 44:1-44:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{li_et_al:LIPIcs.STACS.2023.44,
  author =	{Li, Haohong and Xia, Ge},
  title =	{{An 𝒪(3.82^k) Time FPT Algorithm for Convex Flip Distance}},
  booktitle =	{40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023)},
  pages =	{44:1--44:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-266-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{254},
  editor =	{Berenbrink, Petra and Bouyer, Patricia and Dawar, Anuj and Kant\'{e}, Mamadou Moustapha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2023.44},
  URN =		{urn:nbn:de:0030-drops-176965},
  doi =		{10.4230/LIPIcs.STACS.2023.44},
  annote =	{Keywords: Flip distance, Rotation distance, Triangulations, Exact algorithms, Parameterized complexity}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2021.48
Streaming Algorithms for Graph k-Matching with Optimal or Near-Optimal Update Time

Authors: Jianer Chen, Qin Huang, Iyad Kanj, Qian Li, and Ge Xia

Published in: LIPIcs, Volume 212, 32nd International Symposium on Algorithms and Computation (ISAAC 2021)

Abstract
We present streaming algorithms for the graph k-matching problem in both the insert-only and dynamic models. Our algorithms, while keeping the space complexity matching the best known upper bound, have optimal or near-optimal update time, significantly improving on previous results. More specifically, for the insert-only streaming model, we present a one-pass randomized algorithm that runs in optimal 𝒪(k²) space and has optimal 𝒪(1) update time, and that, w.h.p. (with high probability), computes a maximum weighted k-matching of a weighted graph. Previously, the best upper bound on the update time was 𝒪(log k), which was achieved by a deterministic streaming algorithm that however only works for unweighted graphs [Stefan Fafianie and Stefan Kratsch, 2014]. For the dynamic streaming model, we present a one-pass randomized algorithm that, w.h.p., computes a maximum weighted k-matching of a weighted graph in Õ(Wk²) space and with Õ(1) update time, where W is the number of distinct edge weights. Again the update time of our algorithm improves the previous best upper bound Õ(k²) [Rajesh Chitnis et al., 2016]. Moreover, we prove that in the dynamic streaming model, any randomized streaming algorithm for the problem requires k²⋅ Ω(W(log W+1)) bits of space. Hence, both the space and update-time complexities achieved by our algorithm in the dynamic model are near-optimal. A streaming approximation algorithm for k-matching is also presented, whose space complexity matches the best known upper bound with a significantly improved update time.
Cite as

Jianer Chen, Qin Huang, Iyad Kanj, Qian Li, and Ge Xia. Streaming Algorithms for Graph k-Matching with Optimal or Near-Optimal Update Time. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 48:1-48:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{chen_et_al:LIPIcs.ISAAC.2021.48,
  author =	{Chen, Jianer and Huang, Qin and Kanj, Iyad and Li, Qian and Xia, Ge},
  title =	{{Streaming Algorithms for Graph k-Matching with Optimal or Near-Optimal Update Time}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{48:1--48:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-214-3},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{212},
  editor =	{Ahn, Hee-Kap and Sadakane, Kunihiko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2021.48},
  URN =		{urn:nbn:de:0030-drops-154816},
  doi =		{10.4230/LIPIcs.ISAAC.2021.48},
  annote =	{Keywords: streaming algorithms, matching, parameterized algorithms, lower bounds}
}
Document
DOI: 10.4230/LIPIcs.ITP.2021.32
Verifying an HTTP Key-Value Server with Interaction Trees and VST

Authors: Hengchu Zhang, Wolf Honoré, Nicolas Koh, Yao Li, Yishuai Li, Li-Yao Xia, Lennart Beringer, William Mansky, Benjamin Pierce, and Steve Zdancewic

Published in: LIPIcs, Volume 193, 12th International Conference on Interactive Theorem Proving (ITP 2021)

Abstract
We present a networked key-value server, implemented in C and formally verified in Coq. The server interacts with clients using a subset of the HTTP/1.1 protocol and is specified and verified using interaction trees and the Verified Software Toolchain. The codebase includes a reusable and fully verified C string library that provides 17 standard POSIX string functions and 17 general purpose non-POSIX string functions. For the KVServer socket system calls, we establish a refinement relation between specifications at user-space level and at CertiKOS kernel-space level.
Cite as

Hengchu Zhang, Wolf Honoré, Nicolas Koh, Yao Li, Yishuai Li, Li-Yao Xia, Lennart Beringer, William Mansky, Benjamin Pierce, and Steve Zdancewic. Verifying an HTTP Key-Value Server with Interaction Trees and VST. In 12th International Conference on Interactive Theorem Proving (ITP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 193, pp. 32:1-32:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{zhang_et_al:LIPIcs.ITP.2021.32,
  author =	{Zhang, Hengchu and Honor\'{e}, Wolf and Koh, Nicolas and Li, Yao and Li, Yishuai and Xia, Li-Yao and Beringer, Lennart and Mansky, William and Pierce, Benjamin and Zdancewic, Steve},
  title =	{{Verifying an HTTP Key-Value Server with Interaction Trees and VST}},
  booktitle =	{12th International Conference on Interactive Theorem Proving (ITP 2021)},
  pages =	{32:1--32:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-188-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{193},
  editor =	{Cohen, Liron and Kaliszyk, Cezary},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2021.32},
  URN =		{urn:nbn:de:0030-drops-139273},
  doi =		{10.4230/LIPIcs.ITP.2021.32},
  annote =	{Keywords: formal verification, Coq, HTTP, deep specification}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2016.64
Information Cascades on Arbitrary Topologies

Authors: Jun Wan, Yu Xia, Liang Li, and Thomas Moscibroda

Published in: LIPIcs, Volume 55, 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)

Abstract
In this paper, we study information cascades on graphs. In this setting, each node in the graph represents a person. One after another, each person has to take a decision based on a private signal as well as the decisions made by earlier neighboring nodes. Such information cascades commonly occur in practice and have been studied in complete graphs where everyone can overhear the decisions of every other player. It is known that information cascades can be fragile and based on very little information, and that they have a high likelihood of being wrong. Generalizing the problem to arbitrary graphs reveals interesting insights. In particular, we show that in a random graph G(n,q), for the right value of q, the number of nodes making a wrong decision is logarithmic in n. That is, in the limit for large n, the fraction of players that make a wrong decision tends to zero. This is intriguing because it contrasts to the two natural corner cases: empty graph (everyone decides independently based on his private signal) and complete graph (all decisions are heard by all nodes). In both of these cases a constant fraction of nodes make a wrong decision in expectation. Thus, our result shows that while both too little and too much information sharing causes nodes to take wrong decisions, for exactly the right amount of information sharing, asymptotically everyone can be right. We further show that this result in random graphs is asymptotically optimal for any topology, even if nodes follow a globally optimal algorithmic strategy. Based on the analysis of random graphs, we explore how topology impacts global performance and construct an optimal deterministic topology among layer graphs.
Cite as

Jun Wan, Yu Xia, Liang Li, and Thomas Moscibroda. Information Cascades on Arbitrary Topologies. In 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 55, pp. 64:1-64:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{wan_et_al:LIPIcs.ICALP.2016.64,
  author =	{Wan, Jun and Xia, Yu and Li, Liang and Moscibroda, Thomas},
  title =	{{Information Cascades on Arbitrary Topologies}},
  booktitle =	{43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)},
  pages =	{64:1--64:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-013-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{55},
  editor =	{Chatzigiannakis, Ioannis and Mitzenmacher, Michael and Rabani, Yuval and Sangiorgi, Davide},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2016.64},
  URN =		{urn:nbn:de:0030-drops-63417},
  doi =		{10.4230/LIPIcs.ICALP.2016.64},
  annote =	{Keywords: Information Cascades, Herding Effect, Random Graphs}
}
Document
Extended Abstract
DOI: 10.4230/LIPIcs.STACS.2008.1368
A Theory for Valiant's Matchcircuits (Extended Abstract)

Authors: Angsheng Li and Mingji Xia

Published in: LIPIcs, Volume 1, 25th International Symposium on Theoretical Aspects of Computer Science (2008)

Abstract
The computational function of a matchgate is represented by its character matrix. In this article, we show that all nonsingular character matrices are closed under matrix inverse operation, so that for every $k$, the nonsingular character matrices of $k$-bit matchgates form a group, extending the recent work of Cai and Choudhary (2006) of the same result for the case of $k=2$, and that the single and the two-bit matchgates are universal for matchcircuits, answering a question of Valiant (2002).
Cite as

Angsheng Li and Mingji Xia. A Theory for Valiant's Matchcircuits (Extended Abstract). In 25th International Symposium on Theoretical Aspects of Computer Science. Leibniz International Proceedings in Informatics (LIPIcs), Volume 1, pp. 491-502, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2008)

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@InProceedings{li_et_al:LIPIcs.STACS.2008.1368,
  author =	{Li, Angsheng and Xia, Mingji},
  title =	{{A Theory for Valiant's Matchcircuits}},
  booktitle =	{25th International Symposium on Theoretical Aspects of Computer Science},
  pages =	{491--502},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-06-4},
  ISSN =	{1868-8969},
  year =	{2008},
  volume =	{1},
  editor =	{Albers, Susanne and Weil, Pascal},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2008.1368},
  URN =		{urn:nbn:de:0030-drops-13686},
  doi =		{10.4230/LIPIcs.STACS.2008.1368},
  annote =	{Keywords: Pfaffian, Matchgate, Matchcircuit}
}
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