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Documents authored by Li, Liang

Found 8 Possible Name Variants:

Li, Liang

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.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}
}

Liang, Suihong

Document
DOI: 10.4230/DagSemProc.05142.3
An Architecture for Tetherless Communication

Authors: Aaditeshwar Seth, Patrick Darragh, Suihong Liang, Yunfeng Lin, and Srinivasan Keshav

Published in: Dagstuhl Seminar Proceedings, Volume 5142, Disruption Tolerant Networking (2005)

Abstract
In the emerging paradigm of tetherless computing, client applications running on small, inexpensive, and smart mobile devices maintain opportunistic wireless connectivity with back-end services running on centralized computers, enabling novel classes of applications. These applications require a communications infrastrastructure that is mobility-aware, disconnection-resilient and provides support for an opportunistic style of communiction. It should even be able to function across network partitions that may arise when end-to-end communication is not possible. We outline, design, and evaluate the implementation of an architecture that provides this functionality. we shot that it is possible for next-generation mobile devices to obtain up to 80-fold improvement over conventional mechanisms by exploiting opportunistic WiFi links, and that this benefit can be delivered as an overlay that is compatible with the current Internet.
Cite as

Aaditeshwar Seth, Patrick Darragh, Suihong Liang, Yunfeng Lin, and Srinivasan Keshav. An Architecture for Tetherless Communication. In Disruption Tolerant Networking. Dagstuhl Seminar Proceedings, Volume 5142, pp. 1-13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2005)

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@InProceedings{seth_et_al:DagSemProc.05142.3,
  author =	{Seth, Aaditeshwar and Darragh, Patrick and Liang, Suihong and Lin, Yunfeng and Keshav, Srinivasan},
  title =	{{An Architecture for Tetherless Communication}},
  booktitle =	{Disruption Tolerant Networking},
  pages =	{1--13},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{5142},
  editor =	{Marcus Brunner and Lars Eggert and Kevin Fall and J\"{o}rg Ott and Lars Wolf},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.05142.3},
  URN =		{urn:nbn:de:0030-drops-3519},
  doi =		{10.4230/DagSemProc.05142.3},
  annote =	{Keywords: Delay tolerant networks, Opportunistic communication, Tetherless computing, Wireless, Mobile}
}

Liang, Shanshan

Document
DOI: 10.4230/LIPIcs.ICLP.2012.26
Answering Why and How questions with respect to a frame-based knowledge base: a preliminary report

Authors: Chitta Baral, Nguyen Ha Vo, and Shanshan Liang

Published in: LIPIcs, Volume 17, Technical Communications of the 28th International Conference on Logic Programming (ICLP'12) (2012)

Abstract
Being able to answer questions with respect to a given text is the cornerstone of language understanding and at the primary school level students are taught how to answer various kinds of questions including why and how questions. In the building of automated question answering systems the focus so far has been more on factoid questions and comparatively little attention has been devoted to answering why and how questions. In this paper we explore answering why and how questions with respect to a frame-based knowledge base and give algorithms and ASP (answer set programming) implementation to answer two classes of questions in the Biology domain. They are of the form: "How are X and Y related in the process Z?" and "Why is X important to Y?"
Cite as

Chitta Baral, Nguyen Ha Vo, and Shanshan Liang. Answering Why and How questions with respect to a frame-based knowledge base: a preliminary report. In Technical Communications of the 28th International Conference on Logic Programming (ICLP'12). Leibniz International Proceedings in Informatics (LIPIcs), Volume 17, pp. 26-36, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{baral_et_al:LIPIcs.ICLP.2012.26,
  author =	{Baral, Chitta and Ha Vo, Nguyen and Liang, Shanshan},
  title =	{{Answering Why and How questions with respect to a frame-based knowledge base: a preliminary report}},
  booktitle =	{Technical Communications of the 28th International Conference on Logic Programming (ICLP'12)},
  pages =	{26--36},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-43-9},
  ISSN =	{1868-8969},
  year =	{2012},
  volume =	{17},
  editor =	{Dovier, Agostino and Santos Costa, V{\'\i}tor},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICLP.2012.26},
  URN =		{urn:nbn:de:0030-drops-36078},
  doi =		{10.4230/LIPIcs.ICLP.2012.26},
  annote =	{Keywords: answer set programming, frame based knowledge representation, question answering.}
}

Liang, Yingyu

Document
DOI: 10.4230/LIPIcs.ITCS.2018.5
Matrix Completion and Related Problems via Strong Duality

Authors: Maria-Florina Balcan, Yingyu Liang, David P. Woodruff, and Hongyang Zhang

Published in: LIPIcs, Volume 94, 9th Innovations in Theoretical Computer Science Conference (ITCS 2018)

Abstract
This work studies the strong duality of non-convex matrix factorization problems: we show that under certain dual conditions, these problems and its dual have the same optimum. This has been well understood for convex optimization, but little was known for non-convex problems. We propose a novel analytical framework and show that under certain dual conditions, the optimal solution of the matrix factorization program is the same as its bi-dual and thus the global optimality of the non-convex program can be achieved by solving its bi-dual which is convex. These dual conditions are satisfied by a wide class of matrix factorization problems, although matrix factorization problems are hard to solve in full generality. This analytical framework may be of independent interest to non-convex optimization more broadly. We apply our framework to two prototypical matrix factorization problems: matrix completion and robust Principal Component Analysis (PCA). These are examples of efficiently recovering a hidden matrix given limited reliable observations of it. Our framework shows that exact recoverability and strong duality hold with nearly-optimal sample complexity guarantees for matrix completion and robust PCA.
Cite as

Maria-Florina Balcan, Yingyu Liang, David P. Woodruff, and Hongyang Zhang. Matrix Completion and Related Problems via Strong Duality. In 9th Innovations in Theoretical Computer Science Conference (ITCS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 94, pp. 5:1-5:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{balcan_et_al:LIPIcs.ITCS.2018.5,
  author =	{Balcan, Maria-Florina and Liang, Yingyu and Woodruff, David P. and Zhang, Hongyang},
  title =	{{Matrix Completion and Related Problems via Strong Duality}},
  booktitle =	{9th Innovations in Theoretical Computer Science Conference (ITCS 2018)},
  pages =	{5:1--5:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-060-6},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{94},
  editor =	{Karlin, Anna R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2018.5},
  URN =		{urn:nbn:de:0030-drops-83583},
  doi =		{10.4230/LIPIcs.ITCS.2018.5},
  annote =	{Keywords: Non-Convex Optimization, Strong Duality, Matrix Completion, Robust PCA, Sample Complexity}
}

Li, Yuliang

Document
DOI: 10.4230/LIPIcs.ICDT.2019.11
Index-Based, High-Dimensional, Cosine Threshold Querying with Optimality Guarantees

Authors: Yuliang Li, Jianguo Wang, Benjamin Pullman, Nuno Bandeira, and Yannis Papakonstantinou

Published in: LIPIcs, Volume 127, 22nd International Conference on Database Theory (ICDT 2019)

Abstract
Given a database of vectors, a cosine threshold query returns all vectors in the database having cosine similarity to a query vector above a given threshold. These queries arise naturally in many applications, such as document retrieval, image search, and mass spectrometry. The present paper considers the efficient evaluation of such queries, providing novel optimality guarantees and exhibiting good performance on real datasets. We take as a starting point Fagin’s well-known Threshold Algorithm (TA), which can be used to answer cosine threshold queries as follows: an inverted index is first built from the database vectors during pre-processing; at query time, the algorithm traverses the index partially to gather a set of candidate vectors to be later verified against the similarity threshold. However, directly applying TA in its raw form misses significant optimization opportunities. Indeed, we first show that one can take advantage of the fact that the vectors can be assumed to be normalized, to obtain an improved, tight stopping condition for index traversal and to efficiently compute it incrementally. Then we show that one can take advantage of data skewness to obtain better traversal strategies. In particular, we show a novel traversal strategy that exploits a common data skewness condition which holds in multiple domains including mass spectrometry, documents, and image databases. We show that under the skewness assumption, the new traversal strategy has a strong, near-optimal performance guarantee. The techniques developed in the paper are quite general since they can be applied to a large class of similarity functions beyond cosine.
Cite as

Yuliang Li, Jianguo Wang, Benjamin Pullman, Nuno Bandeira, and Yannis Papakonstantinou. Index-Based, High-Dimensional, Cosine Threshold Querying with Optimality Guarantees. In 22nd International Conference on Database Theory (ICDT 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 127, pp. 11:1-11:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{li_et_al:LIPIcs.ICDT.2019.11,
  author =	{Li, Yuliang and Wang, Jianguo and Pullman, Benjamin and Bandeira, Nuno and Papakonstantinou, Yannis},
  title =	{{Index-Based, High-Dimensional, Cosine Threshold Querying with Optimality Guarantees}},
  booktitle =	{22nd International Conference on Database Theory (ICDT 2019)},
  pages =	{11:1--11:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-101-6},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{127},
  editor =	{Barcelo, Pablo and Calautti, Marco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2019.11},
  URN =		{urn:nbn:de:0030-drops-103135},
  doi =		{10.4230/LIPIcs.ICDT.2019.11},
  annote =	{Keywords: Vector databases, Similarity search, Cosine, Threshold Algorithm}
}

Liang, Xiao

Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2020.28
Improved Black-Box Constructions of Composable Secure Computation

Authors: Rohit Chatterjee, Xiao Liang, and Omkant Pandey

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
We close the gap between black-box and non-black-box constructions of composable secure multiparty computation in the plain model under the minimal assumption of semi-honest oblivious transfer. The notion of protocol composition we target is angel-based security, or more precisely, security with super-polynomial helpers. In this notion, both the simulator and the adversary are given access to an oracle called an angel that can perform some predefined super-polynomial time task. Angel-based security maintains the attractive properties of the universal composition framework while providing meaningful security guarantees in complex environments without having to trust anyone. Angel-based security can be achieved using non-black-box constructions in max(R_OT,Õ(log n)) rounds where R_OT is the round-complexity of semi-honest oblivious transfer. However, current best known black-box constructions under the same assumption require max(R_OT,Õ(log² n)) rounds. If R_OT is a constant, the gap between non-black-box and black-box constructions can be a multiplicative factor log n. We close this gap by presenting a max(R_OT,Õ(log n)) round black-box construction. We achieve this result by constructing constant-round 1-1 CCA-secure commitments assuming only black-box access to one-way functions.
Cite as

Rohit Chatterjee, Xiao Liang, and Omkant Pandey. Improved Black-Box Constructions of Composable Secure Computation. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 28:1-28:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{chatterjee_et_al:LIPIcs.ICALP.2020.28,
  author =	{Chatterjee, Rohit and Liang, Xiao and Pandey, Omkant},
  title =	{{Improved Black-Box Constructions of Composable Secure Computation}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{28:1--28:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.28},
  URN =		{urn:nbn:de:0030-drops-124351},
  doi =		{10.4230/LIPIcs.ICALP.2020.28},
  annote =	{Keywords: Secure Multi-Party Computation, Black-Box, Composable, Non-Malleable}
}

Liang, JiaJian

Document
DOI: 10.4230/LIPIcs.ISAAC.2021.39
Multimodal Transportation with Ridesharing of Personal Vehicles

Authors: Qian-Ping Gu and JiaJian Liang

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

Abstract
Many public transportation systems are unable to keep up with growing passenger demand as the population grows in urban areas. The slow or lack of improvement for public transportation pushes people to use private transportation modes, such as carpooling and ridesharing. However, the occupancy rate of personal vehicles has been dropping in many cities. In this paper, we describe a centralized transit system that integrates public transit and ridesharing, which matches drivers and transit riders such that the riders would result in shorter travel time using both transit and ridesharing. The optimization goal of the system is to assign as many riders to drivers as possible for ridesharing. We give an exact approach and approximation algorithms to achieve the optimization goal. As a case study, we conduct an extensive computational study to show the effectiveness of the transit system for different approximation algorithms, based on the real-world traffic data in Chicago City; the data sets include both public transit and ridesharing trip information. The experiment results show that our system is able to assign more than 60% of riders to drivers, leading to a substantial increase in occupancy rate of personal vehicles and reducing riders' travel time.
Cite as

Qian-Ping Gu and JiaJian Liang. Multimodal Transportation with Ridesharing of Personal Vehicles. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 39:1-39:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{gu_et_al:LIPIcs.ISAAC.2021.39,
  author =	{Gu, Qian-Ping and Liang, JiaJian},
  title =	{{Multimodal Transportation with Ridesharing of Personal Vehicles}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{39:1--39:16},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2021.39},
  URN =		{urn:nbn:de:0030-drops-154727},
  doi =		{10.4230/LIPIcs.ISAAC.2021.39},
  annote =	{Keywords: Multimodal transportation, ridesharing, approximation algorithms, computational study}
}

Liang, Ya-Chun

Document
DOI: 10.4230/LIPIcs.ESA.2024.48
Scheduling with Obligatory Tests

Authors: Konstantinos Dogeas, Thomas Erlebach, and Ya-Chun Liang

Published in: LIPIcs, Volume 308, 32nd Annual European Symposium on Algorithms (ESA 2024)

Abstract
Motivated by settings such as medical treatments or aircraft maintenance, we consider a scheduling problem with jobs that consist of two operations, a test and a processing part. The time required to execute the test is known in advance while the time required to execute the processing part becomes known only upon completion of the test. We use competitive analysis to study algorithms for minimizing the sum of completion times for n given jobs on a single machine. As our main result, we prove using a novel analysis technique that the natural 1-SORT algorithm has competitive ratio at most 1.861. For the special case of uniform test times, we show that a simple threshold-based algorithm has competitive ratio at most 1.585. We also prove a lower bound that shows that no deterministic algorithm can be better than √2-competitive even in the case of uniform test times.
Cite as

Konstantinos Dogeas, Thomas Erlebach, and Ya-Chun Liang. Scheduling with Obligatory Tests. In 32nd Annual European Symposium on Algorithms (ESA 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 308, pp. 48:1-48:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dogeas_et_al:LIPIcs.ESA.2024.48,
  author =	{Dogeas, Konstantinos and Erlebach, Thomas and Liang, Ya-Chun},
  title =	{{Scheduling with Obligatory Tests}},
  booktitle =	{32nd Annual European Symposium on Algorithms (ESA 2024)},
  pages =	{48:1--48:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-338-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{308},
  editor =	{Chan, Timothy and Fischer, Johannes and Iacono, John and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2024.48},
  URN =		{urn:nbn:de:0030-drops-211194},
  doi =		{10.4230/LIPIcs.ESA.2024.48},
  annote =	{Keywords: Competitive ratio, Online algorithm, Scheduling with testing, Sum of completion times}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2022.28
Improving the Bounds of the Online Dynamic Power Management Problem

Authors: Ya-Chun Liang, Kazuo Iwama, and Chung-Shou Liao

Published in: LIPIcs, Volume 248, 33rd International Symposium on Algorithms and Computation (ISAAC 2022)

Abstract
We investigate the power-down mechanism which decides when a machine transitions between states such that the total energy consumption, characterized by execution cost, idle cost and switching cost, is minimized. In contrast to most of the previous studies on the offline model, we focus on the online model in which a sequence of jobs with their release time, execution time and deadline, arrive in an online fashion. More precisely, we exploit a different switching on and off strategy and present an upper bound of 3, and further show a lower bound of 2.1, in a dual-machine model, introduced by Chen et al. in 2014 [STACS 2014: 226-238], both of which beat the currently best result.
Cite as

Ya-Chun Liang, Kazuo Iwama, and Chung-Shou Liao. Improving the Bounds of the Online Dynamic Power Management Problem. In 33rd International Symposium on Algorithms and Computation (ISAAC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 248, pp. 28:1-28:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{liang_et_al:LIPIcs.ISAAC.2022.28,
  author =	{Liang, Ya-Chun and Iwama, Kazuo and Liao, Chung-Shou},
  title =	{{Improving the Bounds of the Online Dynamic Power Management Problem}},
  booktitle =	{33rd International Symposium on Algorithms and Computation (ISAAC 2022)},
  pages =	{28:1--28:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-258-7},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{248},
  editor =	{Bae, Sang Won and Park, Heejin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2022.28},
  URN =		{urn:nbn:de:0030-drops-173138},
  doi =		{10.4230/LIPIcs.ISAAC.2022.28},
  annote =	{Keywords: Online algorithm, Energy scheduling, Dynamic power management}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2021.50
Tight Competitive Analyses of Online Car-Sharing Problems

Authors: Ya-Chun Liang, Kuan-Yun Lai, Ho-Lin Chen, and Kazuo Iwama

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

Abstract
The car-sharing problem, proposed by Luo, Erlebach and Xu in 2018, mainly focuses on an online model in which there are two locations: 0 and 1, and k total cars. Each request which specifies its pick-up time and pick-up location (among 0 and 1, and the other is the drop-off location) is released in each stage a fixed amount of time before its specified start (i.e. pick-up) time. The time between the booking (i.e. released) time and the start time is enough to move empty cars between 0 and 1 for relocation if they are not used in that stage. The model, called kS2L-F, assumes that requests in each stage arrive sequentially regardless of the same booking time and the decision (accept or reject) must be made immediately. The goal is to accept as many requests as possible. In spite of only two locations, the analysis does not seem easy and the (tight) competitive ratio (CR) is only known to be 2.0 for k = 2 and 1.5 for a restricted value of k, i.e., a multiple of three. In this paper, we remove all the holes of unknown CR’s; namely we prove that the CR is 2k/(k + ⌊k/3⌋) for all k ≥ 2. Furthermore, if the algorithm can delay its decision until all requests have come in each stage, the CR is improved to roughly 4/3. We can take this advantage even further, precisely we can achieve a CR of (2+R)/3 if the number of requests in each stage is at most Rk, 1 ≤ R ≤ 2, where we do not have to know the value of R in advance. Finally we demonstrate that randomization also helps to get (slightly) better CR’s.
Cite as

Ya-Chun Liang, Kuan-Yun Lai, Ho-Lin Chen, and Kazuo Iwama. Tight Competitive Analyses of Online Car-Sharing Problems. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 50:1-50:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{liang_et_al:LIPIcs.ISAAC.2021.50,
  author =	{Liang, Ya-Chun and Lai, Kuan-Yun and Chen, Ho-Lin and Iwama, Kazuo},
  title =	{{Tight Competitive Analyses of Online Car-Sharing Problems}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{50:1--50:14},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2021.50},
  URN =		{urn:nbn:de:0030-drops-154835},
  doi =		{10.4230/LIPIcs.ISAAC.2021.50},
  annote =	{Keywords: Car-sharing, Competitive analysis, On-line scheduling, Randomized algorithm}
}
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