scholarly journals An Instance Data Repository for the Round-robin Sports Timetabling Problem

2020 ◽  
Vol 45 (2) ◽  
pp. 184-200
Author(s):  
David Van Bulck ◽  
Dries Goossens ◽  
Jo¨rn Scho¨nberger ◽  
Mario Guajardo

The sports timetabling problem is a combinatorial optimization problem that consists of creating a timetable that defines against whom, when and where teams play games. This is a complex matter, since real-life sports timetabling applications are typically highly constrained. The vast amount and variety of constraints and the lack of generally accepted benchmark problem instances make that timetable algorithms proposed in the literature are often tested on just one or two specific seasons of the competition under consideration. This is problematic since only a few algorithmic insights are gained. To mitigate this issue, this article provides a problem instance repository containing over 40 different types of instances covering artificial and real-life problem instances. The construction of such a repository is not trivial, since there are dozens of constraints that need to be expressed in a standardized format. For this, our repository relies on RobinX, an XML-supported classification framework. The resulting repository provides a (non-exhaustive) overview of most real-life sports timetabling applications published over the last five decades. For every problem, a short description highlights the most distinguishing characteristics of the problem. The repository is publicly available and will be continuously updated as new instances or better solutions become available.

Algorithms ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 5 ◽  
Author(s):  
Víctor Pacheco-Valencia ◽  
José Alberto Hernández ◽  
José María Sigarreta ◽  
Nodari Vakhania

The Traveling Salesman Problem (TSP) aims at finding the shortest trip for a salesman, who has to visit each of the locations from a given set exactly once, starting and ending at the same location. Here, we consider the Euclidean version of the problem, in which the locations are points in the two-dimensional Euclidean space and the distances are correspondingly Euclidean distances. We propose simple, fast, and easily implementable heuristics that work well, in practice, for large real-life problem instances. The algorithm works on three phases, the constructive, the insertion, and the improvement phases. The first two phases run in time O ( n 2 ) and the number of repetitions in the improvement phase, in practice, is bounded by a small constant. We have tested the practical behavior of our heuristics on the available benchmark problem instances. The approximation provided by our algorithm for the tested benchmark problem instances did not beat best known results. At the same time, comparing the CPU time used by our algorithm with that of the earlier known ones, in about 92% of the cases our algorithm has required less computational time. Our algorithm is also memory efficient: for the largest tested problem instance with 744,710 cities, it has used about 50 MiB, whereas the average memory usage for the remained 217 instances was 1.6 MiB.


2021 ◽  
Vol 8 ◽  
Author(s):  
Radu Mariescu-Istodor ◽  
Pasi Fränti

The scalability of traveling salesperson problem (TSP) algorithms for handling large-scale problem instances has been an open problem for a long time. We arranged a so-called Santa Claus challenge and invited people to submit their algorithms to solve a TSP problem instance that is larger than 1 M nodes given only 1 h of computing time. In this article, we analyze the results and show which design choices are decisive in providing the best solution to the problem with the given constraints. There were three valid submissions, all based on local search, including k-opt up to k = 5. The most important design choice turned out to be the localization of the operator using a neighborhood graph. The divide-and-merge strategy suffers a 2% loss of quality. However, via parallelization, the result can be obtained within less than 2 min, which can make a key difference in real-life applications.


2021 ◽  
Vol 68 (3) ◽  
pp. 16-40
Author(s):  
Grzegorz Koloch ◽  
Michał Lewandowski ◽  
Marcin Zientara ◽  
Grzegorz Grodecki ◽  
Piotr Matuszak ◽  
...  

We optimise a postal delivery problem with time and capacity constraints imposed on vehicles and nodes of the logistic network. Time constraints relate to the duration of routes, whereas capacity constraints concern technical characteristics of vehicles and postal operation outlets. We consider a method which can be applied to a brownfield scenario, in which capacities of outlets can be relaxed and prospective hubs identified. As a solution, we apply a genetic algorithm and test its properties both in small case studies and in a simulated problem instance of a larger (i.e. comparable with real-world instances) size. We show that the genetic operators we employ are capable of switching between solutions based on direct origin-to-destination routes and solutions based on transfer connections, depending on what is more beneficial in a given problem instance. Moreover, the algorithm correctly identifies cases in which volumes should be shipped directly, and those in which it is optimal to use transfer connections within a single problem instance, if an instance in question requires such a selection for optimality. The algorithm is thus suitable for determining hubs and satellite locations. All considerations presented in this paper are motivated by real-life problem instances experienced by the Polish Post, the largest postal service provider in Poland, in its daily plans of delivering postal packages, letters and pallets.


2021 ◽  
Vol 47 (2) ◽  
pp. 674-685
Author(s):  
Ushindi Limota ◽  
Egbert Mujuni ◽  
Allen Mushi

Many mathematical optimization problems from real-life applications are NP-hard, and hence no algorithm that solves them to optimality within a reasonable time is known. For this reason, metaheuristic methods are mostly preferred when their size is big. Many meta-heuristic methods have been proposed to solve various combinatorial optimization problems. One of the newly introduced metaheuristic methods is a bat-inspired algorithm, which is based on the echolocation behaviour of microbats. Bat algorithm (BA) and its variants have been used successfully to solve several optimization problems. However, from the No-free Lunch Theorem, it is known that there is no universal metaheuristic method that can solve efficiently all optimization problems. Thus, this study work focused on investigating the usefulness of BA in solving an optimization problem called Course Teaching Problem (CTP). Since BA was originally designed to solve continuous problems, and CTP is a combinatorial optimization problem, a discrete version of BA for CPT has been proposed and tested using real-life data from the Dar es Salaam University College of Education (DUCE). The algorithm has produced promising results, as in each execution test, it generated a timetable in which all hard constraints were met and soft constraints were significantly satisfied within a few iterations. Keywords: Combinatorial optimization, Timetabling problem, Metaheuristic algorithms, Bat algorithm.


2018 ◽  
Vol 4 (10) ◽  
pp. 6
Author(s):  
Khemchandra Patel ◽  
Dr. Kamlesh Namdev

Age changes cause major variations in the appearance of human faces. Due to many lifestyle factors, it is difficult to precisely predict how individuals may look with advancing years or how they looked with "retreating" years. This paper is a review of age variation methods and techniques, which is useful to capture wanted fugitives, finding missing children, updating employee databases, enhance powerful visual effect in film, television, gaming field. Currently there are many different methods available for age variation. Each has their own advantages and purpose. Because of its real life applications, researchers have shown great interest in automatic facial age estimation. In this paper, different age variation methods with their prospects are reviewed. This paper highlights latest methodologies and feature extraction methods used by researchers to estimate age. Different types of classifiers used in this domain have also been discussed.


Author(s):  
فتحي بن جمعة أحمد

ملخص البحث تعدّ هذه المحاولة في دراسة مجالات التفسير الموضوعي ومنهجية البحث فيه  مفتاحا لبعض القضايا المتعلقة بالموضوع، ومدخلا لدراسة التفسير الموضوعي يسهل على طلاب العلم والباحثين فهم كلام الله، وتدبر معانيه، والاهتداء به، والقيام ببحوث تطبيقية في مجالات التفسير الموضوعي. فقد بينت أن مجالات البحث في التفسير الموضوعي أربعة وهي البحث في المصطلح، والموضوع، والمحاور، والوحدة الموضوعيّة في السورة القرآنيّة. وقد أكدت أن البحث في محاور القرآن الكريم من مجالات البحث في التفسير الموضوعي التي لم تحظَ باهتمام الباحثين، ثم توسعت في سوق الأدلة والبراهين الدالة على أن الوحدة الموضوعية للسورة القرآنيّة مجال أساس من مجالات البحث في التفسير الموضوعي الذي لا ينبغي إغفاله، وإهمال شأنه. ثم بحثت في موضوع منهجيّة البحث في التفسير الموضوعي، ونظراً للخلط أوالاضطراب الذي بدا لدى بعض الباحثين في هذا الصدد، وضحت المقدمات المنهجيّة العامة الضرورية للبحث في التفسير الموضوعي ثم حاولت رسم الإطار التصوري والمنهجي العام والضوابط الأساسية التي يجب أن يتبعها الباحث إذا أراد الكتابة في التفسير الموضوعي. ثم بيّنت الخطوات الأساسيّة للبحث في التفسير الموضوعي ومنها حرية الباحث في اختيار موضوع بحثه والاطلاع على أكبر عدد ممكن من التفاسير بمختلف أنواعها مع الاستفادة من التراث البشري في حقول المعرفة المتنوعة على أن تكون الهيمنة للقرآن أولا وأخيرا على الكتب الأخرى والنظريات البشرية. الكلمات الرئيسة: القرآن، تفسير، موضوعي، مجالات، منهج. Abstract This article is an attempt to address the issue of the scopes and research methodology in the thematic commentary of the Holy Qur’Én. It could be considered as an introductory work for students and researchers who are interested in this field of research which will help them develop a good understanding of the meanings and teachings of the Qur’Én and its application to the real life. It may also help them undertake case studies and research in the field of thematic commentary of the Qur’Én. It has been explained in the article that the scope of the thematic commentary of the Qur’Én includes four areas; i.e. the concept, the topic, the central themes and the thematic unity of the SËrah/Chapter. The article gives a special emphasis on the study of the Qur’Énic central themes as it was overlooked by some researchers. It also provides a systematic investigation on the thematic unity of the SËrah/Chapter and considers it a significant area of research in the thematic commentary of the Qur’Én. The article also addresses the issue of the research methodology in the field of the thematic commentary of the Qur’Én. In this regard, the author highlights the principles, conditions and framework for undertaking research projects in this field of study and explains the major steps that should be followed in the execution of the research. These steps include freedom of choosing the research topic, freedom of benefitting from different types of tafsÊr (interpretation of the Qur’Én) works and schools and benefitting from the human heritage in different fields of knowledge, provided that the Qur’Én should have controlling power on other books and human theories.   Key Words: The Qur’Én, TafsÊr, Thematic, Scopes, Methodology. Abstrak Artikel ini ialah satu percubaan menangani isu  skop dan metodologi penyelidikan dalam tafsiran Al-Qur’Én Holy mengikut tema. Ia boleh dianggap sebagai satu kajian permulaan untuk pelajar-pelajar dan sarjana-sarjana yang meminati bidang ini penyelidikan yang akan membantu mereka merangka satu pemahaman yang baik tentang makna-makna dan ajaran-ajaran Qur’Én dan perlaksanaannya dalam kehidupan sebenar. Ia mungkin juga  dapat membantu mereka menjalankan kajian kes dalam bidang penyelidikan tafsiran Al-Qur’Én mengikut tema. Artikel ini akan menjelaskan  skop tafsiran Al-Qur’Én mengikut  tema ini merangkumi empat bidang:  konsep tafsiran mengikut tema, topiknya, tema-tema kecil dan tema umum Surah Al-Qur’Én. Artikel ini memberi satu penekanan khas pada kajian tafsiran Al-Qur’Én mengikut  tema kerana ia agak kurang mendapat perhatian beberapa penyelidik. Ia juga menampilkan satu kajian sistematik pada pemahaman tema Surah dalam Al-Qur’Én dan menganggapnya satu bidang penyelidikan penting dalam kajian tafsiran Al-Qur’Én mengikut tema. Artikel juga memberikan perhatian kepada bidang metodologi penyelidikan terhadap usaha tafsiran Al-Qur’Én secara bertema. Dalam hal ini, pengkaji akan menonjolkan prinsip-prinsip, syarat-syarat dan rangka kerja untuk projek-projek projek penyelidikan dalam lapangan ini dan menerangkan langkah-langkah utama yang harus diikuti dalam pelaksanaan penyelidikan yang berkenaan. Lang-langkah ini termasuk kebebasan memilih tajuk penyelidikan, kebebasan dalam mengambil  manfaat daripada jenis-jenis tafsiran Qur’Én yang berbeza serta sekolah-sekolah pemikiran yang berbeza dalam aliran tafsir serta rangka bagaimana memanfaatkan warisan tamadun manusia berlandaskan ajaran Al-Qur’Én. Kata Kunci: Al-Qur’Én, TafsÊr, Tema, Bidang-bidang, Metodologi.


Algorithms ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 187
Author(s):  
Aaron Barbosa ◽  
Elijah Pelofske ◽  
Georg Hahn ◽  
Hristo N. Djidjev

Quantum annealers, such as the device built by D-Wave Systems, Inc., offer a way to compute solutions of NP-hard problems that can be expressed in Ising or quadratic unconstrained binary optimization (QUBO) form. Although such solutions are typically of very high quality, problem instances are usually not solved to optimality due to imperfections of the current generations quantum annealers. In this contribution, we aim to understand some of the factors contributing to the hardness of a problem instance, and to use machine learning models to predict the accuracy of the D-Wave 2000Q annealer for solving specific problems. We focus on the maximum clique problem, a classic NP-hard problem with important applications in network analysis, bioinformatics, and computational chemistry. By training a machine learning classification model on basic problem characteristics such as the number of edges in the graph, or annealing parameters, such as the D-Wave’s chain strength, we are able to rank certain features in the order of their contribution to the solution hardness, and present a simple decision tree which allows to predict whether a problem will be solvable to optimality with the D-Wave 2000Q. We extend these results by training a machine learning regression model that predicts the clique size found by D-Wave.


2021 ◽  
Vol 13 (2) ◽  
pp. 973
Author(s):  
Gigel Paraschiv ◽  
Georgiana Moiceanu ◽  
Gheorghe Voicu ◽  
Mihai Chitoiu ◽  
Petru Cardei ◽  
...  

Our paper presents the hammer mill working process optimization problem destined for milling energetic biomass (MiscanthusGiganteus and Salix Viminalis). For the study, functional and constructive parameters of the hammer mill were taken into consideration in order to reduce the specific energy consumption. The energy consumption dependency on the mill rotor spinning frequency and on the sieve orifices in use, as well as on the material feeding flow, in correlation with the vegetal biomass milling degree was the focus of the analysis. For obtaining this the hammer mill was successively equipped with 4 different types of hammers that grind the energetic biomass, which had a certain humidity content and an initial degree of reduction ratio of the material. In order to start the optimization process of hammer mill working process, 12 parameters were defined. The objective functions which minimize hammer mill energy consumption and maximize the milled material percentage with a certain specific granulation were established. The results obtained can serve as the basis for choosing the optimal working, constructive, and functional parameters of hammer mills in this field, and for a better design of future hammer mills.


2017 ◽  
Vol 35 (4) ◽  
pp. 369-381 ◽  
Author(s):  
Jussi Vimpari ◽  
Seppo Junnila

Purpose Retail properties are a perfect example of a property class where revenues determine the rent for the property owners. Estimating the value of new retail developments is challenging, as the initial revenues can have a significant variance from the long-term revenue levels. Owners and tenants try to manage this problem by introducing different kind of options, such as overage rent and extension rights, to the lease contracts. The purpose of this paper is to value these options through time for different types of retailers, using real-life data with a method that can be easily applied in practice. Design/methodology/approach This paper builds upon the existing papers on real option studies but has a strong practical focus, which has been identified as a challenge in the field. The paper presents simple mathematical equations for valuing overage rent and extension options. The equations capture the value related to uncertainty (volatility) that is missed by standard valuation practices. Findings The results indicate that overage and extension options can represent a significant proportion of retail lease contract’s value and their value is heavily time-dependent. The option values differ greatly between tenants, as the volatilities can have a large spread across tenants. The paper suggests that the applicability of option pricing theory and calculus should not be considered as an insurmountable barrier any more, rather a greater challenge for the practical adaptability of the method can be the availability of real-life data that is a common problem in real option analysis. Practical implications The value of extension and overage options varies greatly between tenants. In general, the property owner can try balance the positive effects from the overage rents to the negative effects of tenant extensions. However, this study tries to highlight that, as usual, using the “law of averages” can result into poor valuation in this context as well. Even the data used in this study provide valuable findings for the property owner as an analytical deduction can be made that certain types of tenants have higher volatilities and this should be acknowledged when valuing options within lease contracts. Originality/value Previous literature in this topic often takes the input data for the option valuation as granted rather than trying to identify the real-life data available for the calculation. This is a common problem in real options valuation and it seems to be one of the reasons why option valuation has not been used widely in practice. This study has used real-life data to assess the problem and more importantly assessed the data across different types of tenants. The volatility spread between different types of tenants has not been discussed previously, even though it has a significant importance when using option pricing in practice.


2018 ◽  
Vol 8 (10) ◽  
pp. 1730 ◽  
Author(s):  
Md. Safiuddin ◽  
A. Kaish ◽  
Chin-Ong Woon ◽  
Sudharshan Raman

Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.


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