5 Search Results for "Guo, Alan"

Document
DOI: 10.4230/LIPIcs.SEA.2023.14
A Graph-Theoretic Formulation of Exploratory Blockmodeling

Authors: Alexander Bille, Niels Grüttemeier, Christian Komusiewicz, and Nils Morawietz

Published in: LIPIcs, Volume 265, 21st International Symposium on Experimental Algorithms (SEA 2023)

Abstract
We present a new simple graph-theoretic formulation of the exploratory blockmodeling problem on undirected and unweighted one-mode networks. Our formulation takes as input the network G and the maximum number t of blocks for the solution model. The task is to find a minimum-size set of edge insertions and deletions that transform the input graph G into a graph G' with at most t neighborhood classes. Herein, a neighborhood class is a maximal set of vertices with the same neighborhood. The neighborhood classes of G' directly give the blocks and block interactions of the computed blockmodel. We analyze the classic and parameterized complexity of the exploratory blockmodeling problem, provide a branch-and-bound algorithm, an ILP formulation and several heuristics. Finally, we compare our exact algorithms to previous ILP-based approaches and show that the new algorithms are faster for t ≥ 4.
Cite as

Alexander Bille, Niels Grüttemeier, Christian Komusiewicz, and Nils Morawietz. A Graph-Theoretic Formulation of Exploratory Blockmodeling. In 21st International Symposium on Experimental Algorithms (SEA 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 265, pp. 14:1-14:20, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@InProceedings{bille_et_al:LIPIcs.SEA.2023.14,
  author =	{Bille, Alexander and Gr\"{u}ttemeier, Niels and Komusiewicz, Christian and Morawietz, Nils},
  title =	{{A Graph-Theoretic Formulation of Exploratory Blockmodeling}},
  booktitle =	{21st International Symposium on Experimental Algorithms (SEA 2023)},
  pages =	{14:1--14:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-279-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{265},
  editor =	{Georgiadis, Loukas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2023.14},
  URN =		{urn:nbn:de:0030-drops-183648},
  doi =		{10.4230/LIPIcs.SEA.2023.14},
  annote =	{Keywords: Clustering, Exact Algorithms, ILP-Formulation, Branch-and-Bound, Social Networks}
}
Document
DOI: 10.4230/LITES-v005-i001-a001
Risk-Aware Scheduling of Dual Criticality Job Systems Using Demand Distributions

Authors: Bader Naim Alahmad and Sathish Gopalakrishnan

Published in: LITES, Volume 5, Issue 1 (2018). Leibniz Transactions on Embedded Systems, Volume 5, Issue 1

Abstract
We pose the problem of scheduling Mixed Criticality (MC) job systems when there are only two criticality levels, Lo and Hi -referred to as Dual Criticality job systems- on a single processing platform, when job demands are probabilistic and their distributions are known. The current MC models require that the scheduling policy allocate as little execution time as possible to Lo-criticality jobs if the scenario of execution is of Hi criticality, and drop Lo-criticality jobs entirely as soon as the execution scenario's criticality level can be inferred and is Hi. The work incurred by "incorrectly" scheduling Lo-criticality jobs in cases of Hi realized scenarios might affect the feasibility of Hi criticality jobs; we quantify this work and call it Work Threatening Feasibility (WTF). Our objective is to construct online scheduling policies that minimize the expected WTF for the given instance, and under which the instance is feasible in a probabilistic sense that is consistent with the traditional deterministic definition of MC feasibility. We develop a probabilistic framework for MC scheduling, where feasibility is defined in terms of (chance) constraints on the probabilities that Lo and Hi jobs meet their deadlines. The probabilities are computed over the set of sample paths, or trajectories, induced by executing the policy, and those paths are dependent upon the set of execution scenarios and the given demand distributions. Our goal is to exploit the information provided by job distributions to compute the minimum expected WTF below which the given instance is not feasible in probability, and to compute a (randomized) "efficiently implementable" scheduling policy that realizes the latter quantity. We model the problem as a Constrained Markov Decision Process (CMDP) over a suitable state space and a finite planning horizon, and show that an optimal (non-stationary) Markov randomized scheduling policy exists. We derive an optimal policy by solving a Linear Program (LP). We also carry out quantitative evaluations on select probabilistic MC instances to demonstrate that our approach potentially outperforms current MC scheduling policies.
Cite as

Bader Naim Alahmad and Sathish Gopalakrishnan. Risk-Aware Scheduling of Dual Criticality Job Systems Using Demand Distributions. In LITES, Volume 5, Issue 1 (2018). Leibniz Transactions on Embedded Systems, Volume 5, Issue 1, pp. 01:1-01:30, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)

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@Article{alahmad_et_al:LITES-v005-i001-a001,
  author =	{Alahmad, Bader Naim and Gopalakrishnan, Sathish},
  title =	{{Risk-Aware Scheduling of Dual Criticality Job Systems Using Demand Distributions}},
  booktitle =	{LITES, Volume 5, Issue 1 (2018)},
  pages =	{01:1--01:30},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2018},
  volume =	{5},
  number =	{1},
  editor =	{Alahmad, Bader Naim and Gopalakrishnan, Sathish},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v005-i001-a001},
  doi =		{10.4230/LITES-v005-i001-a001},
  annote =	{Keywords: Mixed criticalities, Probability distribution, Real time systems, Scheduling, Chance constrained Markov decision process, Linear programming, Randomized policy}
}
Document
DOI: 10.4230/LITES-v004-i001-a002
Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results

Authors: Florian Kluge

Published in: LITES, Volume 4, Issue 1 (2017). Leibniz Transactions on Embedded Systems, Volume 4, Issue 1

Abstract
The concept of a firm real-time task implies the notion of a firm deadline that should not be missed by the jobs of this task. If a deadline miss occurs, the concerned job yields no value to the system. For some applications domains, this restrictive notion can be relaxed. For example, robust control systems can tolerate that single executions of a control loop miss their deadlines, and still yield an acceptable behaviour. Thus, systems can be developed under more optimistic assumptions, e.g. by allowing overloads. However, care must be taken that deadline misses do not accumulate. This restriction can be expressed by the model of (m,k)-firm real-time tasks that require that from any k consecutive jobs at least m are executed successfully. In this article, we extend our prior work on the MKU scheduling heuristic. MKU uses history-cognisant utility functions as means for making decisions in overload situations. We present new theoretical results on MKU and on other schedulers for (m,k)-firm real-time tasks. Based on extensive simulations, we assess the performance of these schedulers. The results allow us to identify task set characteristics that can be used as guidelines for choosing a scheduler for a concrete use case.
Cite as

Florian Kluge. Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results. In LITES, Volume 4, Issue 1 (2017). Leibniz Transactions on Embedded Systems, Volume 4, Issue 1, pp. 02:1-02:25, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)

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@Article{kluge:LITES-v004-i001-a002,
  author =	{Kluge, Florian},
  title =	{{Utility-Based Scheduling of (m,k)-firm Real-Time Tasks - New Empirical Results}},
  booktitle =	{LITES, Volume 4, Issue 1 (2017)},
  pages =	{02:1--02:25},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2017},
  volume =	{4},
  number =	{1},
  editor =	{Kluge, Florian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v004-i001-a002},
  doi =		{10.4230/LITES-v004-i001-a002},
  annote =	{Keywords: Real-time Scheduling, (m, k)-Firm Real-Time Tasks}
}
Document
DOI: 10.4230/LITES-v001-i002-a003
Implementing Mixed-criticality Systems Upon a Preemptive Varying-speed Processor

Authors: Zhishan Guo and Sanjoy K. Baruah

Published in: LITES, Volume 1, Issue 2 (2014). Leibniz Transactions on Embedded Systems, Volume 1, Issue 2

Abstract
A mixed criticality (MC) workload consists of components of varying degrees of importance (or "criticalities"); the more critical components typically need to have their correctness validated to greater levels of assurance than the less critical ones. The problem of executing such a MC workload upon a preemptive processor whose effective speed may vary during run-time, in a manner that is not completely known prior to run-time, is considered.Such a processor is modeled as being characterized by several execution speeds: a normal speed and several levels of degraded speed. Under normal circumstances it will execute at or above its normal speed; conditions during run-time may cause it to execute slower. It is desired that all components of the MC workload execute correctly under normal circumstances. If the processor speed degrades, it should nevertheless remain the case that the more critical components execute correctly (although the less critical ones need not do so).In this work, we derive an optimal algorithm for scheduling MC workloads upon such platforms; achieving optimality does not require that the processor be able to monitor its own run-time speed. For the sub-case of the general problem where there are only two criticality levels defined, we additionally provide an implementation that is asymptotically optimal in terms of run-time efficiency.
Cite as

Zhishan Guo and Sanjoy K. Baruah. Implementing Mixed-criticality Systems Upon a Preemptive Varying-speed Processor. In LITES, Volume 1, Issue 2 (2014). Leibniz Transactions on Embedded Systems, Volume 1, Issue 2, pp. 03:1-03:19, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2014)

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@Article{guo_et_al:LITES-v001-i002-a003,
  author =	{Guo, Zhishan and Baruah, Sanjoy K.},
  title =	{{Implementing Mixed-criticality Systems Upon a Preemptive Varying-speed Processor}},
  booktitle =	{LITES, Volume 1, Issue 2 (2014)},
  pages =	{03:1--03:19},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2014},
  volume =	{1},
  number =	{2},
  editor =	{Guo, Zhishan and Baruah, Sanjoy K.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v001-i002-a003},
  doi =		{10.4230/LITES-v001-i002-a003},
  annote =	{Keywords: Mixed criticalities, Varying-speed processor, Preemptive uniprocessor scheduling, }
}
Document
DOI: 10.4230/LIPIcs.APPROX-RANDOM.2014.737
List Decoding Group Homomorphisms Between Supersolvable Groups

Authors: Alan Guo and Madhu Sudan

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

Abstract
We show that the set of homomorphisms between two supersolvable groups can be locally list decoded up to the minimum distance of the code, extending the results of Dinur et al. (Proc. STOC 2008) who studied the case where the groups are abelian. Moreover, when specialized to the abelian case, our proof is more streamlined and gives a better constant in the exponent of the list size. The constant is improved from about 3.5 million to 105.
Cite as

Alan Guo and Madhu Sudan. List Decoding Group Homomorphisms Between Supersolvable Groups. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 28, pp. 737-747, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2014)

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@InProceedings{guo_et_al:LIPIcs.APPROX-RANDOM.2014.737,
  author =	{Guo, Alan and Sudan, Madhu},
  title =	{{List Decoding Group Homomorphisms Between Supersolvable Groups}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)},
  pages =	{737--747},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2014.737},
  URN =		{urn:nbn:de:0030-drops-47359},
  doi =		{10.4230/LIPIcs.APPROX-RANDOM.2014.737},
  annote =	{Keywords: Group theory, error-correcting codes, locally decodable codes}
}
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