Wyniki wyszukiwania - BazTech

1

Efficient Approximation Methods for Lexicographic Max-Min Optimization

Śliwiński Tomasz

Journal of Telecommunications and Information Technology

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2024

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nr 1

46--53

EN

Lexicographic max-min (LMM) optimization is of considerable importance in many fairness-oriented applications. LMM problems can be reformulated in a way that allows to solve them by applying the standard lexicographic maximization algorithm. However, the reformulation introduces a large number of auxiliary variables and linear constraints, making the process computationally complex. In this paper, two approximation schemes for such a reformulation are presented, resulting in problem size reduction and significant performance gains. Their influence on the quality of the solution is shown in a series of computational experiments concerned with the fair network dimensioning and bandwidth allocation problem.

2

The SEKO assignment : efficient and fair assignment of students to multiple seminars

Hoßfeld Tobias

Operations Research and Decisions

|

2023

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Vol. 33, No. 3

1--25

EN

Seminars are offered to students for education in various disciplines. The seminars may be limited in terms of the maximum number of participants, e.g., to have lively interactions. Due to capacity limitations, those seminars are often offered several times to serve the students’ demands. Still, some seminars are more popular than others and it may not be possible to grant access to all interested students due to capacity limitations. In this paper, a simple, but efficient random selection using key objectives (SEKO) assignment strategy is proposed which achieves the following goals: (i) efficiency by utilizing all available seminar places, (ii) satisfying all students by trying to assign at least one seminar to each student, and (iii) fairness by considering the number of assigned seminars per student. We formulate various theoretical optimization models using integer linear programming (ILP) and compare their solutions to the SEKO assignment based on a real-world data set. The real-world data set is also used as the basis for generating large data sets to investigate the scalability in terms of demand and number of seminars. Furthermore, the first-in first-out (FIFO) assignment, as a typical implementation of fair assignments in practice, is compared to SEKO in terms of utilization and fairness. The results show that the FIFO assignment suffers in realworld situations regarding fairness, while the SEKO assignment is close to the optimum and scales regarding computational time in contrast to the ILP.

3

Sustainable development as a concept of fairness from the perspective of energy consumption policy

Pieńkowski Dariusz

Ekonomia i Środowisko

|

2019

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nr 3

180--196

EN

Classical economists have claimed that selfish behaviour and competition are the most efficient way of resource allocation. Their concept of fairness according to one’s work was treated as the universal formula of resource allocation very much defined by the individualistic perspective. However, the concept of sustainable development refers to the idea of fairness according to the needs of both present and future generations. This paper presents the sustainable perspective of fairness that postulates new forms of energy consumption related to the concepts of solidarity or social economies. The perspective is contrasted with the example of Friedman’s view, a famous advocate of market economy, to illustrate the differences and consequences for socio-economic development. Both the fairness systems are just in the terms of formal justice, despite the dispute regarding their fairness formula; and this paper presents a strategy to the consumption of energy based on a reference point, which utilizes these two formulas to allocation energy resources. Additionally, this study seeks to present the role of the new socio-technical structures, which provide opportunities to create a wide range of goals beyond the narrow targets of energy production from renewables, including reduction of social and economic inequality or generation of social capital and resilient economies.

4

Antecedents predicting coaches’ intentions to remain in sport organisations

Surujlal J., Dhurup M.

Polish Journal of Management Studies

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2017

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Vol. 16, No. 1

234--247

EN

In order to acquire optimal performance from coaches, sport organisations provide various mechanisms in an attempt to improve their management of sport coaches. Demonstrating support for their coaches, by proving adequate resources and rewards, proper supervisor support, organisational fairness, organisational support afforded to coaches are vehicles through which organizations’ management can elicit the optimal performance from their workforce. The study is located within a quantitative research paradigm and adopts a cross sectional survey to collect data from 151 coaches who were purposefully selected from various sport organisations in the Gauteng province of South Africa. The results of the regression analysis demonstrate that rewards, supervisor support and organisational support are strong predictors for coaches to remain within their current organisation. Organisational fairness seems to negatively impact on coaches intention to remain within their respective organisations. It is recommended that in managing sport coaches sport organisations should create a favourable environment that positively nurtures coaches’ intentions to remain within their current organisations. More specifically, the current reward system, the organization’s fairness towards coaches, support from supervisors and general organisational support should be a target for enhancement in order to foster the relationship between coaches and their respective organisation that they work for. These antecedents can offer insights that are particularly valuable to coaches’ management and sport organisations seeking to nurture interactions with their coaches in order for them to remain in their current organisation.

PL

Aby uzyskać optymalną wydajność coachów, organizacje sportowe zapewniają różne mechanizmy w celu poprawy zarządzania coachami sportowymi. Organizacje sportowe wspierają swoich coachów, poprzez zapewnienie odpowiednich zasobów i nagród, odpowiednie wsparcie ze strony przełożonych czy uczciwość organizacyjną. Wsparcie organizacyjne przyznawane coachom to pojazdy, za pomocą których kierownictwo organizacji może uzyskać optymalną wydajność ze strony swoich pracowników. Badanie przeprowadzono w ramach ilościowego paradygmatu badań, w celu zebrania danych od 151 trenerów, którzy zostali celowo wybrani z różnych organizacji sportowych w prowincji Gauteng w RPA, przyjęto ankietę przekrojową. Wyniki analizy regresji pokazują, że nagrody, wsparcie zwierzchników, jak i wsparcie organizacyjne, są silnymi predykatorami dla coachów do pozostania w ich obecnej organizacji. Sprawiedliwość organizacyjna zdaje się negatywnie wpływać na intencje coachów do pozostania w swoich organizacjach. Zaleca się, aby w zarządzaniu coachami sportowymi organizacje sportowe tworzyły sprzyjające warunki, które pozytywnie wspierają ich zamiary pozostania w swoich obecnych organizacjach. Mówiąc dokładniej, obecny system nagród, uczciwość organizacji wobec coachów, wsparcie ze strony przełożonych i ogólne wsparcie organizacyjne powinno być celem ulepszania i rozwijania relacji między coachami a organizacją, dla której pracują. Te okoliczności poprzedzające mogą zapewnić wgląd, który jest szczególnie cenny dla kierownictwa coachów i organizacji sportowych, pragnących pielęgnować interakcje z ich coachami, aby mogli pozostać w swojej obecnej organizacji.

5

A Survey on Mac Protocols for Wireless Sensor Networks

Anubhama R., Rajendran T.

Annals of Computer Science and Information Systems

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2017

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Vol. 10

121--126

EN

Wireless Sensor Network (WSN) is an infrastructure-less wireless network of nodes that can sense the environment or physical conditions and relay the data to a sink or a gateway possibly through multiple hops. The primary task of Medium Access Control (MAC) protocols in such a network is to synchronize the task of data communication between the nodes with energy efficiency being the prime consideration due to power constraints in sensor nodes. So the most significant performance specifications for MAC protocols in WSN are throughput, efficiency, stability, fairness, low access delay, low transmission delay and low overhead. In this paper we have surveyed significant classes of MAC protocols used in WSN and reviewed the merits and demerits of those protocols based on the aforementioned specifications.

6

Simultaneous routing and flow rate optimization in energy-aware computer networks

Jaskóła P., Arabas P., Karbowski A.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 1

231--243

EN

The issue of energy-aware traffic engineering has become prominent in telecommunications industry in the last years. This paper presents a two-criteria network optimization problem, in which routing and bandwidth allocation are determined jointly, so as to minimize the amount of energy consumed by a telecommunication infrastructure and to satisfy given demands represented by a traffic matrix. A scalarization of the criteria is proposed and the choice of model parameters is discussed in detail. The model of power dissipation as a function of carried traffic in a typical software router is introduced. Then the problem is expressed in a form suitable for the mixed integer quadratic programming (MIQP) solver. The paper is concluded with a set of small, illustrative computational examples. Computed solutions are implemented in a testbed to validate the accuracy of energy consumption models and the correctness of the proposed traffic engineering algorithm.

7

A scheme of resource allocation and stability for peer-to-peer file-sharing networks

Li S., Sun W., E C. G., Shi L.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 3

707--719

EN

Peer-to-peer (P2P) networks offer a cost-effective and easily deployable framework for sharing content. However, P2P file-sharing applications face a fundamental problem of unfairness. Pricing is regarded as an effective way to provide incentives to peers to cooperate. In this paper we propose a pricing scheme to achieve reasonable resource allocation in P2P file-sharing networks, and give an interpretation for the utility maximization problem and its sub-problems from an economic point of view. We also deduce the exact expression of optimal resource allocation for each peer, and confirm it with both simulation and optimization software. In order to realize the optimum in a decentralized architecture, we present a novel price-based algorithm and discuss its stability based on Lyapunov stability theory. Simulation results confirm that the proposed algorithm can attain an optimum within reasonable convergence times.

8

The need of fairness in group consensus reaching process in a fuzzy environment

Gołuńska D., Hołda M.

Czasopismo Techniczne. Automatyka

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2013

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R. 110, z. 1-AC

29--38

EN

In this paper we explain the need of "fairness" in the human-consistent computational system which supports a group consensus reaching process. We propose the model which combines mathematical approach based on fuzzy environment, i.e. “soft” consensus developed by Kacprzyk and Fedrizzi and socio-psychological approach concerning fairness component. We view fairness from two possible perspectives: a fair distribution and a fair final decision. Finally, we confirm our assumptions by observations in the analyzed groups of students.

PL

W niniejszym artykule wyjaśniono potrzebę „sprawiedliwości” w systemie obliczeniowym wspomagającym proces osiągania konsensusu w grupie decydentów. Autorki zaproponowały model łączący podejście matematyczne oparte na środowisku rozmytym oraz czynniki społeczno-psychologiczne wyjaśniające opisywaną koncepcję. Pojęcie „sprawiedliwości” rozpatrywane jest tu w dwóch kategoriach: rozkładu zasobów oraz decyzji ostatecznej. Założenia poparte są wnioskami na podstawie obserwacji grup studentów.

9

On the optimization of the inter - flow fairness in the Internet

Adamczyk B., Chydziński A.

Theoretical and Applied Informatics

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2012

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Vol. 24, No. 3

205-225

EN

All known active queue management algorithms invented to provide fair bandwidth allocation between TCP flows are designed to cooperate with the classic TCP congestion control (New Reno). However, some new congestion control schemes are becoming more and more popular nowadays (e.g. the Cubic algorithm). Therefore, the following question arises: will these fair queue management algorithms work well in the presence of a new congestion control scheme? To answer this questions, we present a comprehensive study of the performance of seven fair queue management algorithms in the presence of seven TCP variants. In particular, the fairness index, queue size and throughput were measured in scenarios with diversified RTTs, traffic patterns and congestion levels. Not only do the results allow us to answer the aforementioned question, but also to formulate recommendation on how to provide the best cross-layer fairness optimization in the Internet.

PL

Wszystkie znane z literatury algorytmy aktywnego zarządzania kolejkami (AQM) ukierunkowane na zapewnienie sprawiedliwego podziału pasma pomiędzy przepływy w Internecie były opracowywane z myślą o współpracy z (klasycznym dziś) algorytmem kontroli zatłoczenia TCP, tzn. New Reno. W ostatnich latach można zauważyć w Internecie istotne zwiększanie się udziału nowych algorytmów kontroli zatłoczenia TCP (jak np. algorytmu Cubic). Dlatego te˙z pojawia się naturalne pytanie: czy algorytmy sprawiedliwego podziału pasma zaprojektowane dla New Reno bedą równie dobrze działać w obecnosci tych nowych wariantów TCP? Aby uzyskać odpowiedź na to pytanie, przeprowadzone zostały szeroko zakrojone studia symulacyjne. Studia te uwzględniały siedem najważniejszych algorytmów AQM do sprawiedliwego podziału pasma, siedem wersji TCP (w tym najnowocześniejsze warianty), różne scenariusze zatłoczenia sieci oraz czasy RTT połączeń TCP. Uzyskane wyniki pozwoliły nie tylko udzielić odpowiedzi na sformułowane powyżej pytanie, ale także wskazać, które wersje TCP i AQM najlepiej realizują ideę optymalizacji międzywarstwowej w celu zapewnienia sprawiedliwego podziału pasma pomiędzy przepływy w Internecie.

10

The Concept of Fairness in the Group Decision Support Systems – a Socio-Psychological Approach

Gołuńska D., Kacprzyk J.

Journal of Applied Computer Science Methods

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2012

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Vol. 4 No. 2

21--29

EN

In this paper we present ae general concept of the consensus reaching process supporting by the group decision support systems. We proposed the idea which combines the mathematical direction based on “soft” consensus developed by Kacprzyk and Zadrożny [6] and relevant socio-psychological factor concerning fairness component. Essentially, we divide fairness approach in consensus reaching process on two possible directions: a fair distribution (fair resource allocation) and a fair final decision. We stress the benefits resulting from the implementation of proposed concept in the group decision support systems and point the direction of further model formalization.

11

Different aspects of supporting group consensus reaching process under fuzziness

Falkiewicz D., Kacprzyk J.

Czasopismo Techniczne. Automatyka

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2012

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R. 109, z. 1-AC

17--27

EN

In this paper we present human-consistent approach of multi-model consensus reaching process supporting by group decision support systems. We consider the idea developed by Kacprzyk and Zadrożny [9, 10, 12] which is related to the “soft” consensus, and where the core of the system is based on fuzzy logic. Essentially, we attempt to stress the multi-model architecture of considering system and distinguish several aspects, i.e. model of agent, model of moderator, model of consensus achievement. Moreover, we present a novel concept based on fair consensus as a meaningful point of further development.

PL

W niniejszym artykule zaprezentowano wybrane aspekty złożonego procesu osiągania konsensusu nadzorowanego przez systemy wspierające podejmowanie decyzji w grupie. Rozważono ideę opracowaną przez Kacprzyka i Zadrożnego [9, 10, 12] powiązaną z terminem „miękkiego” konsensus, opartą na logice rozmytej. Przedstawiono złożoną architekturę rozważanego systemu oraz rozróżniono w nim kilka aspektów, tj. model agenta, model moderatora, model osiągania konsensusu. Ponadto, zaprezentowano nową koncepcję opartą na sprawiedliwym konsensusie jako punkt wyjścia dla dalszych badań.

12

On Deadlock and Fairness Decision Problems for Computations on Client-server Systems

Czaja L.

Fundamenta Informaticae

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2011

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Vol. 109, nr 3

255-264

EN

Phenomena that inherently happen in distributed computing - some types of deadlock and fairness or starvation - are examined in a client-server model. Messages travelling between clients and a server are: request for an action, permission to start it, and termination of its execution. Deadlock-prone and (un)fair behaviours are formulated for the model and equivalence of the respective formulae to formulae expressing emptiness and finiteness of some sets generated by the model is established. From these results, some answers to decision problems for the aforesaid properties are obtained. Furthermore, equivalence between the so-called strong fairness (specified by first-order formula) and weak-fairness (second-order formula) is demonstrated

13

Associativity of Infinite Synchronized Shuffles and Team Automata

ter Beek M.H., Kleijn J.

Fundamenta Informaticae

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2009

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Vol. 91, nr 3-4

4437-461

EN

Motivated by different ways to obtain team automata from synchronizing component automata, we consider various definitions of synchronized shuffles of words. A shuffle of two words is an interleaving of their symbol occurrenceswhich preserves the original order of these occurrences within each of the two words. In a synchronized shuffle, however, also two occurrences of one symbol, each from a different word, may be identified as a single occurrence. In case at least one of the words involved is infinite, a (synchronized) shuffle can also be unfair in the sense that an infinite word may prevail fromsome point onwards even when the other word still has occurrences to contribute to the shuffle. We prove that for the synchronized shuffle operations under consideration, every (fair or unfair) synchronized shuffle can be obtained as a limit of synchronized shuffles of the finite prefixes of the words involved. In addition, it is shown that with the exception of one, all synchronized shuffle operations that we consider satisfy a natural notion of associativity, also in case of unfairness. Finally, using these results, some compositionality results for team automata are established.

14

Multicriteria models for fair resource allocation

Ogryczak W.

Control and Cybernetics

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2007

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Vol. 36, no 2

303-332

EN

Resource allocation problems are concerned with the allocation of limited resources among competing activities so as to achieve the best performances. However, in systems which serve many users there is a need to respect some fairness rules while looking for the overall efficiency. The so-called Max-Min Fairness is widely used to meet these goals. However, allocating the resource to optimize the worst performance may cause dramatic worsening of the overall system efficiency. Therefore, several other fair allocation schemes are being considered and analyzed. In this paper we show how the concepts of multiple criteria equitable optimization can effectively be used to generate various fair and efficient allocation schemes. First, we demonstrate how the scalar inequality measures can be consistently used in bicriteria models to search for fair and efficient allocations. Further, two alternative multiple criteria models equivalent to equitable optimization are introduced, thus allowing to generate a larger variety of fair and efficient resource allocation schemes.

15

Fair and efficient network dimensioning with the reference point methodology

Goryczak W., Wierzbicki A., Milewski M.

Journal of Telecommunications and Information Technology

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2006

|

nr 4

21-30

EN

The dimensioning of telecommunication networks that carry elastic traffic requires the fulfillment of two conflicting goals: maximizing the total network throughput and providing fairness to all flows. Fairness in telecommunication network design is usually provided using the so-called max-min fairness (MMF) approach. However, this approach maximizes the performance of the worst (most expensive) flows which may cause a large worsening of the overall throughput of the network. In this paper we show how the concepts of multiple criteria equitable optimization can be effectively used to generate various fair and efficient allocation schemes. We introduce a multiple criteria model equivalent to equitable optimization and we develop a corresponding reference point procedure for fair and efficient network dimensioning for elastic flows. The procedure is tested on a sample network dimensioning problem for elastic traffic and its abilities to model various preferences are demonstrated.

16

Telecommunications network design and max-min optimization problem

Ogryczak W., Pióro M., Tomaszewski A.

Journal of Telecommunications and Information Technology

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2005

|

nr 3

43-56

EN

Telecommunications networks are facing increasing demand for Internet services. Therefore, the problem of telecommunications network design with the objective to maximize service data flows and provide fair treatment of all services is very up-to-date. In this application, the so-called max-min fair (MMF) solution concept is widely used to formulate the resource allocation scheme. It assumes that the worst service performance is maximized and the solution is additionally regularized with the lexicographic maximization of the second worst performance, the third one, etc. In this paper we discuss solution algorithms for MMF problems related to telecommunications network design. Due to lexicographic maximization of ordered quantities, the MMF solution concept cannot be tackled by the standard optimization model (mathematical programme). However, one can formulate a sequential lexicographic optimization procedure. The basic procedure is applicable only for convex models, thus it allows to deal with basic design problems but fails if practical discrete restrictions commonly arriving in telecommunications network design are to be taken into account. Then, however, alternative sequential approaches allowing to solve non-convex MMF problems can be used.

17

Fairness considerations with algorithms for elastic traffic routing

Cinkler T., Laborczi P., Pióro M.

Journal of Telecommunications and Information Technology

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2004

|

nr 2

3-12

EN

The bit rate of modern applications typically varies in time. We consider the traffic elastic if the rate of the sources can be controlled as a function of free resources along the route of that traffic. The objective is to route the demands optimally in sense of increasing the total network throughput while setting the rates of sources in a fair way. We propose a new fairness definition the relative fairness that handles lower and upper bounds on the traffic rate of each source and we compare it with two other known fairness definitions, namely, the max-min and the proportional rate fairness. We propose and compare different routing algorithms, all with three types of fairness definitions. The algorithms are all a tradeoff between network throughput, fairness and computational time.

18

Best Fairness Hierarchy in Elementary Nets

Ochmański E.

Fundamenta Informaticae

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2004

|

Vol. 60, nr 1-4

237--250

EN

The fairness hierarchy and conspiracies, the notions introduced by Best, are studied in the context of elementary nets. Proving that sequential as well as persistent systems are conspiracy-free, we indicate two main roots of conspiracies: distributed memory and conflicts. Using the notion of marking-fairness, due to Merceron, we prove that T0-fairness + M0-fairness = T∞-fairness. This result gives a method of a local control ensuring globally fair executions. Next we show how to check, if a given elementary net is conspiracy-free, and prove the obtained criterion to be effectively decidable. Finally, we give a characterization of live concurrent systems, using the notion of ∞ -fairness.

19

On multi-criteria approaches to bandwidth allocation

Ogryczak W., Wierzbicki A.

Control and Cybernetics

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2004

|

Vol. 33, no 3

427-448

EN

Modern telecommunication networks face an increasing demand for services. Among these, an increasing number are services that can adapt to available bandwidth, and are therefore referred to as elastic traffic. Nominal network design for elastic traffic becomes increasingly significant. Typical resource allocation methods are concerned with the allocation of limited resources among competing activities so as to achieve the best overall performance of the system. In the network dimensioning problem for elastic traffic, one needs to allocate bandwidth to maximize service flows and simultaneously to reach a fair treatment of all the elastic services. Thus, both the overall efficiency (throughput) and the fairness (equity) among various services are important. In such applications, the so-called Max-Min Fairness (MMF) solution concept is widely used to formulate the resource allocation scheme. This approach guarantees fairness but may lead to significant losses in the overall throughput of the network. In this paper we show how the concepts of multiple criteria equitable optimization can be effectively used to generate various fair resource allocation schemes. We introduce a multiple criteria model ecluivalent to equitable optimization and we develop a corresponding reference point procedure to generate fair efficient bandwidth allocations. The procedure is tested on a sample network dimensioning problem and its abilities to model various preferences are demonstrated.

20

Fair resource allocation schemes and network dimensioning problems

Ogryczak W., Śliwiński T., Wierzbicki A.

Journal of Telecommunications and Information Technology

|

2003

|

nr 3

34-42

EN

Resource allocation problems are concerned with the allocation of limited resources among competing activities so as to achieve the best overall performances of the system but providing fair treatment of all the competitors. Telecommunication networks are facing the increasing demand for Internet services. Therefore, a problem of network dimensioning with elastic traffic arises which requires to allocate bandwidth to maximize service flows with fair treatment of all the services. In such applications, the so-called max-min fairness (MMF) solution concept is widely used to formulate the resource allocation scheme. This guarantees the fairness but may lead to significant losses in the overall throughput of the network. In this paper we show how multiple criteria optimization concepts can be used to generate various fair resource allocation schemes. The solution concepts are tested on the network dimensioning problem and their abilities to model various preferences are demonstrated.