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124 results on '"Wong, Prudence W.H."'

12. Greedy is Optimal for Online Restricted Assignment and Smart Grid Scheduling for Unit Size Jobs

Author

Liu, Fu-Hong, Liu, Hsiang-Hsuan, Wong, Prudence W.H., Sub Algorithms and Complexity, Algorithms and Complexity, Sub Algorithms and Complexity, and Algorithms and Complexity

Subjects
Schedule, Mathematical optimization, 021103 operations research, Competitive analysis, Matching (graph theory), Optimal online algorithm, Computer science, Restricted assignment, 0211 other engineering and technologies, 0102 computer and information sciences, 02 engineering and technology, Upper and lower bounds, 01 natural sciences, Theoretical Computer Science, Scheduling (computing), Smart grid, Computational Theory and Mathematics, Bounding overwatch, 010201 computation theory & mathematics, Theory of computation, Online algorithm, Greedy algorithm, Assignment problem, Smart grid scheduling
Abstract

We study online scheduling of unit-sized jobs in two related problems, namely, restricted assignment problem and smart grid problem. The input to the two problems are in close analogy but the objective functions are different. We show that the greedy algorithm is an optimal online algorithm for both problems. Typically, an online algorithm is proved to be an optimal online algorithm through bounding its competitive ratio and showing a lower bound with matching competitive ratio. However, our analysis does not take this approach. Instead, we prove the optimality without giving the exact bounds on competitive ratio. Roughly speaking, given any online algorithm and a job instance, we show the existence of another job instance for greedy such that (i) the two instances admit the same optimal offline schedule; (ii) the cost of the online algorithm is at least that of the greedy algorithm on the respective job instance. With these properties, we can show that the competitive ratio of the greedy algorithm is the smallest possible.

Published
2021

38. Off-Line Algorithms for Minimizing Total Flow Time in Broadcast Scheduling.

Author

Wang, Lusheng, Chan, Wun-Tat, Chin, Francis Y.L., Zhang, Yong, Zhu, Hong, Shen, Hong, and Wong, Prudence W.H.

Abstract

We study the off-line broadcast scheduling problem to minimize total (or average) flow time. Assume the server has k pages and the requests arrive at n distinct times, we give the first algorithm to find the optimal schedule for the server with a single channel, in O(k3(n+k)k-1) time. For m-channel case, i.e., the server can broadcast m different pages at a time where m < k, we find the optimal schedule in O(nk-m) time when k and m are constants. In the single channel case, we also give a simple linear-time approximation algorithm to minimize average flow time, which achieves an additive (k-1)/2-approximation. [ABSTRACT FROM AUTHOR]

Published
2005
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39. Dynamic Bin Packing of Unit Fractions Items.

Author

Caires, Luís, Italiano, Giuseppe F., Monteiro, Luís, Palamidessi, Catuscia, Yung, Moti, Wun-Tat Chan, Tak-Wah Lam, and Wong, Prudence W.H.

Abstract

This paper studies the dynamic bin packing problem, in which items arrive and depart at arbitrary time. We want to pack a sequence of unit fractions items (i.e., items with sizes 1/w for some integer w ≥ 1) into unit-size bins such that the maximum number of bins used over all time is minimized. Tight and almost-tight performance bounds are found for the family of any-fit algorithms, including first-fit, best-fit, and worst-fit. We show that the competitive ratio of best-fit and worst-fit is 3, which is tight, and the competitive ratio of first-fit lies between 2.45 and 2.4985. We also show that no on-line algorithm is better than 2.428-competitive. This result improves the lower bound of dynamic bin packing problem even for general items. [ABSTRACT FROM AUTHOR]

Published
2005
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41. EFFICIENT CONSTRAINED MULTIPLE SEQUENCE ALIGNMENT WITH PERFORMANCE GUARANTEE.

Author

Chin, Francis Y.L., Ho, N.L., Lam, T.W., and Wong, Prudence W.H.

Subjects
COMPUTATIONAL biology, BIOINFORMATICS, ALGORITHMS, SPACETIME, ALGEBRA
Abstract

The constrained multiple sequence alignment problem is to align a set of sequences of maximum length n subject to a given constrained sequence, which arises from some knowledge of the structure of the sequences. This paper presents new algorithms for this problem, which are more efficient in terms of time and space (memory) than the previous algorithms,15 and with a worst-case guarantee on the quality of the alignment. Saving the space requirement by a quadratic factor is particularly significant as the previous O(n4)-space algorithm has limited application due to its huge memory requirement. Experiments on real data sets confirm that our new algorithms show improvements in both alignment quality and resource requirements. [ABSTRACT FROM AUTHOR]

Published
2005
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42. Designing an Optimized Water Quality Monitoring Network with Reserved Monitoring Locations.

Author

Zhu, Xiaohui, Yue, Yong, Wong, Prudence W.H., Zhang, Yixin, and Ding, Hao

Subjects
WATER quality, PROBABILITY theory, WATERSHEDS, PARTICLE swarm optimization, WATER pollution
Abstract

The optimized design of water quality monitoring networks can not only minimize the pollution detection time and maximize the detection probability for river systems but also reduce redundant monitoring locations. In addition, it can save investments and costs for building and operating monitoring systems as well as satisfy management requirements. This paper aims to use the beneficial features of multi-objective discrete particle swarm optimization (MODPSO) to optimize the design of water quality monitoring networks. Four optimization objectives: minimum pollution detection time, maximum pollution detection probability, maximum centrality of monitoring locations and reservation of particular monitoring locations, are proposed. To guide the convergence process and keep reserved monitoring locations in the Pareto frontier, we use a binary matrix to denote reserved monitoring locations and develop a new particle initialization procedure as well as discrete functions for updating particle's velocity and position. The storm water management model (SWMM) is used to model a hypothetical river network which was studied in the literature for comparative analysis of our work. We define three pollution detection thresholds and simulate pollution events respectively to obtain all the pollution detection time for all the potential monitoring locations when a pollution event occurs randomly at any potential monitoring locations. Compared to the results of an enumeration search method, we confirm that our algorithm could obtain the Pareto frontier of optimized monitoring network design, and the reserved monitoring locations are included to satisfy the management requirements. This paper makes fundamental advancements of MODPSO and enables it to optimize the design of water quality monitoring networks with reserved monitoring locations. [ABSTRACT FROM AUTHOR]

Published
2019
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43. Sorting by Multi-cut Rearrangements

Author

Bulteau, Laurent, Fertin, Guillaume, Jean, Géraldine, Komusiewicz, Christian, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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44. Role-Based Access Control on Graph Databases

Author

Chabin, Jacques, Ciferri, Cristina D. A., Halfeld-Ferrari, Mirian, Hara, Carmem S., Penteado, Raqueline R. M., Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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45. Iterated Uniform Finite-State Transducers on Unary Languages

Author

Kutrib, Martin, Malcher, Andreas, Mereghetti, Carlo, Palano, Beatrice, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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46. Bike Assisted Evacuation on a Line

Author

Jawhar, Khaled, Kranakis, Evangelos, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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47. Tightness of Sensitivity and Proximity Bounds for Integer Linear Programs

Author

Berndt, Sebastian, Jansen, Klaus, Lassota, Alexandra, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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48. Semi-automatic Column Type Inference for CSV Table Understanding

Author

Bonfitto, Sara, Cappelletti, Luca, Trovato, Fabrizio, Valentini, Giorgio, Mesiti, Marco, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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49. S2CFT: A New Approach for Paper Submission Recommendation

Author

Nguyen, Dac, Huynh, Son, Huynh, Phong, Dinh, Cuong V., Nguyen, Binh T., Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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50. Graphs Cannot Be Indexed in Polynomial Time for Sub-quadratic Time String Matching, Unless SETH Fails

Author

Equi, Massimo, Mäkinen, Veli, Tomescu, Alexandru I., Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Bureš, Tomáš, editor, Dondi, Riccardo, editor, Gamper, Johann, editor, Guerrini, Giovanna, editor, Jurdziński, Tomasz, editor, Pahl, Claus, editor, Sikora, Florian, editor, and Wong, Prudence W.H., editor

Published
2021
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