# Dr Rhyd Lewis

Reader

- lewisr9@cardiff.ac.uk
- +44 (0)29 2087 4856
- M/1.32, Maths and Education Building , Senghennydd Road, Cardiff, CF24 4AG

- Media commentator
- Available for postgraduate supervision

## Overview

Rhyd Lewis is a reader at the School of Mathematics.

### Administrative duties

- Deputy director of internationals
- Co-investigator for the Cardiff University Data Innovation Accelerator (10% FTE)
- Fellow of the Cardiff University Data Innovation Research Institute
- Member of Operational Research Group and the Planning and Optimisation Group

### Personal website

## Biography

Rhyd Lewis is a reader at the School of Mathematics, Cardiff University, Wales. He holds a PhD in computing and operational research (Edinburgh Napier University, 2006) and is the author of the book Graph Colouring: Algorithms and Applications (Springer, 2015).

### Professional memberships

- Fellow of the Higher Education Academy

### Committees and reviewing

- Associate editor for the
*International Journal of Metaheuristics* - Guest editor for the special issue on Algorithms for Graphs and Networks,
*Algorithms,*2020. - Program committee member for Evolutionary Computation in Combinatorial Optimisation (EvoCop)
- Program committee member for the Practice and Theory of Automated Timetabling conference (PATAT)
- Program committee member for the Metaheuristics International Conference (MIC)
- Program committee member for the Genetic and Evolutionary Computation Conference (GECCO).

## Publications

### 2021

- Lewis, R., Thiruvady, D. and Morgan, K. 2021. The maximum happy induced subgraph problem: bounds and algorithms. Computers and Operations Research 126, article number: 105114. (10.1016/j.cor.2020.105114)
- Sciortino, M., Lewis, R. and Thompson, J. 2021. A heuristic algorithm for school bus routing with bus stop selection. Presented at: EvoCOP 2021, Seville, Spain, Apr 2021 Presented at Zarges, C. and Verel, S. eds.Evolutionary Computation in Combinatorial Optimization, Vol. 12692. Lecture Notes in Computer Science/Theoretical Computer Science and General Issues Springer, Cham pp. 202-218., (10.1007%2F978-3-030-72904-2_13)

### 2020

- Thiruvady, D., Lewis, R. and Morgan, K. 2020. Tackling the maximum happy vertices problem in large networks. 4OR: A Quarterly Journal of Operations Research 18, pp. 507-527. (10.1007/s10288-020-00431-4)
- Padungwech, W., Thompson, J. and Lewis, R. 2020. Effects of update frequencies in a dynamic capacitated arc routing problem. Networks 76(4), pp. 522-538. (10.1002/net.21990)
- Lewis, R. 2020. Cite or be damned: some thoughts on reviewer-coerced citation. [Online]. https://scientistsarehumans.com/: Scientists are Humans. Available at: https://scientistsarehumans.com/2020/11/24/cite-or-be-damned-some-thoughts-on-reviewer-coerced-citation/
- Lewis, R. 2020. Editorial for the special issue on “Algorithms for graphs and networks”. Algorithms 13(11), pp. 292. (10.3390/a13110292)
- Lewis, R. 2020. Algorithms for finding shortest paths in networks with vertex transfer penalties. Algorithms 13(11), article number: 269. (10.3390/a13110269)
- Lewis, R. 2020. A shortest path algorithm for graphs featuring transfer costs at their vertices. Presented at: International Conference on Computational Logistics, Enschede, The Netherlands, 28–30 Sept 2020Computational Logistics, Vol. 12433. Springer Verlag pp. 539-552., (10.1007/978-3-030-59747-4_35)
- Lewis, R. 2020. A heuristic algorithm for finding attractive fixed-length circuits in street maps. Presented at: International Conference on Computational Logistics, Enschede, The Netherlands, 28–30 Sept 2020Computational Logistics, Vol. 12433. Springer Verlag pp. 384-395., (10.1007/978-3-030-59747-4_25)
- Kheiri, A.et al. 2020. Constructing operating theatre schedules using partitioned graph colouring techniques. Health Systems (10.1080/20476965.2020.1796530)
- Lewis, R., Anderson, T. and Carroll, F. 2020. Can school enrolment and performance be improved by maximizing students' sense of choice in elective subjects?. Journal of Learning Analytics 7(1), pp. 75-87. (10.18608/jla.2020.71.6)
- Lewis, R. 2020. Five degrees of separation from De Niro - charting the social networks of movie stars. The Conversation
- Lewis, R. 2020. Want to mislead and confuse? use statistics!. [Online]. Scientists are Humans. Available at: https://scientistsarehumans.com/2019/01/26/want-to-mislead-and-confuse-use-statistics/
- Lewis, R. 2020. Who is the centre of the movie universe? Using python and networkX to analyse the social network of movie stars. arXiv. Available at: https://arxiv.org/abs/2002.11103
- Neis, P. and Lewis, R. 2020. Evaluating the influence of parameter setup on the performance of heuristics for the graph colouring problem. International Journal of Metaheuristics 7(4), pp. 352-378.

### 2019

- Lewis, R., Thiruvady, D. and Morgan, K. 2019. Finding happiness: an analysis of the maximum happy vertices problem. Computers and Operations Research 103 (10.1016/j.cor.2018.11.015)

### 2018

- Hawa, A. L., Lewis, R. and Thompson, J. M. 2018. Heuristics for the score-constrained strip-packing problem. Presented at: COCOA 2018: International Conference on Combinatorial Optimization and Applications, Atlanta, GA, USA, 15-17 December 2018 Presented at Kim, D., Uma, R. N. and Zelikovsky, A. eds.Combinatorial Optimization and Applications: 12th International Conference, COCOA 2018, Atlanta, GA, USA, December 15-17, 2018, Proceedings, Vol. 11346. Lecture Notes in Computer Science Springer Verlag pp. 449., (10.1007/978-3-030-04651-4_30)
- Lewis, R. 2018. Two example optimisation problems from the world of education. Presented at: OR Society Annual Conference (OR60), Lancaster, UK, 11-13 Sep 2018.
- Lewis, R. and Smith-Miles, K. 2018. A heuristic algorithm for finding cost-effective solutions to real-world school bus routing problems. Journal of Discrete Algorithms 52-53, pp. 2-17. (10.1016/j.jda.2018.11.001)
- Hardy, B., Lewis, R. and Thompson, J. 2018. Tackling the edge dynamic graph colouring problem with and without future adjacency information. Journal of Heuristics 24, pp. 321-343. (10.1007/s10732-017-9327-z)
- Lewis, R., Smith-Miles, K. and Phillips, K. 2018. The school bus routing problem: An analysis and algorithm. Presented at: IWOCA 2017: 28th International Workshop on Combinatorial Algorithms, Newcastle, NSW, Australia, 17-21 July 2017 Presented at Brankovic, L., Ryan, J. and Smyth, W. F. eds.Combinatorial Algorithms: 28th International Workshop, IWOCA 2017, Newcastle, NSW, Australia, July 17-21, 2017, Revised Selected Papers. Lecture Notes in Computer Science Springer pp. 287-298., (10.1007/978-3-319-78825-8_24)

### 2017

- Lewis, R. and Holborn, P. 2017. How to pack trapezoids: exact and evolutionary algorithms. IEEE Transactions on Evolutionary Computation 21(3), pp. 463-476. (10.1109/TEVC.2016.2609000)

### 2016

- Lewis, R. and Carroll, F. 2016. Creating seating plans: a practical application. Journal of the Operational Research Society 67(11), pp. 1353-1362. (10.1057/jors.2016.34)
- Padungwech, W., Thompson, J. and Lewis, R. 2016. Investigating edge-reordering procedures in a tabu search algorithm for the capacitated arc routing problem. Presented at: HM 2016: International Workshop on Hybrid Metaheuristics, Plymouth, UK, 8-10 June 2016 Presented at Blesa, M. J., Blum, C. and Cangelosi, A. eds.Hybrid Metaheuristics: 10th International Workshop, HM 2016, Plymouth, UK, June 8-10, 2016, Proceedings, Vol. 9668. Lecture Notes in Computer Science Cham: Springer pp. 62-74., (10.1007/978-3-319-39636-1_5)
- Hardy, B., Lewis, R. and Thompson, J. M. 2016. Modifying colourings between time-steps to tackle changes in dynamic random graphs. Presented at: EvoCOP 2016: European Conference on Evolutionary Computation in Combinatorial Optimization, Porto, Portugal, 30 March - 1 April 2016 Presented at Chicano, F., Hu, B. and Garcia-Sanchez, P. eds.Evolutionary Computation in Combinatorial Optimization: 16th European Conference, EvoCOP 2016, Porto, Portugal, March 30 – April 1, 2016, Proceedings, Vol. 9595. Springer pp. 186-201., (10.1007/978-3-319-30698-8_13)
- Lewis, R. 2016. Graph colouring: an ancient problem with modern applications. Impact 3(1), pp. 47-50. (10.1080/2058802X.2016.11963998)
- Kheiri, A.et al. 2016. A Sequence-based selection hyper-heuristic: a case study in nurse rostering. Presented at: PATAT 2016: 11th International Conference on the Practice and Theory of Automated Timetabling, Udine, Italy, 23-26 August 2016 Presented at Burke, E. K. et al. eds.PATAT 2016: Proceedings of the 11th International Conference of the Practice and Theory of Automated Timetabling. pp. 503-505.

### 2015

- Lewis, R. M. R. 2015. A guide to graph colouring: algorithms and applications. Springer. (10.1007/978-3-319-25730-3)
- Lewis, R. and Thompson, J. 2015. Analysing the effects of solution space connectivity with an effective metaheuristic for the course timetabling problem. European Journal of Operational Research 240(3), pp. 637-648. (10.1016/j.ejor.2014.07.041)
- Lewis, R. 2015. Graph coloring and recombination. In: Kacprzyk, J. and Pedrycz, W. eds. Springer Handbook of Computational Intelligence. Springer, pp. 1239-1254.
- Rowse, E. L.et al. 2015. Applying set partitioning methods in the construction of operating theatre schedules. Presented at: International Conference on Theory and Practice in Modern Computing 2015, Las Palmas de Gran Canaria, Spain, 22-24 July 2015.

### 2014

- Smith-Miles, K.et al. 2014. Towards objective measures of algorithm performance across instance space. Computers & Operations Research 45, pp. 12-24. (10.1016/j.cor.2013.11.015)
- Cooper, I.et al. 2014. Optimising large scale public transport network design problems using mixed-mode parallel multi-objective evolutionary algorithms. Presented at: IEEE Congress on Evolutionary Computation, Beijing, China, 6 - 11 July 2014Evolutionary Computation (CEC). IEEE pp. 2841-2848., (10.1109/CEC.2014.6900362)
- John, M. P., Mumford, C. L. and Lewis, R. 2014. An improved multi-objective algorithm for the urban transit routing problem. Presented at: EvoCOP 2014: 14th European Conference on Evolutionary Computation in Combinatorial Optimization, Granada, Spain, 23-25 April 2014 Presented at Blum, C. and Ochoa, G. eds.Evolutionary Computation in Combinatorial Optimisation: 14th European Conference, EvoCOP 2014, Granada, Spain, April 23-25, 2014, Revised Selected Papers, Vol. 8600. Lecture Notes in Computer Science Springer pp. 49-60., (10.1007/978-3-662-44320-0_5)

### 2013

- Lewis, R. and Carroll, F. 2013. The "engaged" interaction: important considerations for the HCI design and development of a web application for solving a complex combinatorial optimization problem. World Journal of Computer Application and Technology 1(3), pp. 75-82.

### 2012

- Lewis, R.et al. 2012. A wide-ranging computational comparison of high-performance graph colouring algorithms. Computers & Operations Research 39(9), pp. 1933-1950. (10.1016/j.cor.2011.08.010)
- Song, X.et al. 2012. An incomplete m-exchange algorithm for solving the large-scale multi-scenario knapsack problem. Computers & Operations Research 39(9), pp. 1988-2000. (10.1016/j.cor.2011.09.012)
- Lewis, R. 2012. A time-dependent metaheuristic algorithm for post enrolment-based course timetabling. Annals of Operations Research 194(1), pp. 273-289. (10.1007/s10479-010-0696-z)
- Holborn, P. L., Thompson, J. M. and Lewis, R. 2012. Combining heuristic and exact methods to solve the vehicle routing problem with pickups, deliveries and time windows. Presented at: EvoCOP 2012: 12th European Conference on Evolutionary Computation in Combinatorial Optimization, Malaga, Spain, 11-13 April 2012 Presented at Hao, J. K. and Middendorf, M. eds.Evolutionary Computation in Combinatorial Optimization: 12th European Conference, EvoCOP 2012, Málaga, Spain, April 11-13, 2012. Proceedings, Vol. 7245. Lecture Notes in Computer Science Springer Verlag pp. 63-74., (10.1007/978-3-642-29124-1_6)

### 2011

- Lewis, R.et al. 2011. An investigation into two bin packing problems with ordering and orientation implications. European Journal of Operational Research 213(1), pp. 52-65. (10.1016/j.ejor.2011.03.016)
- Lewis, R. and Thompson, J. M. 2011. On the application of graph colouring techniques in round-robin sports scheduling. Computers & Operations Research 38(1), pp. 190-204. (10.1016/j.cor.2010.04.012)
- Lewis, R. and Pullin, E. J. 2011. Revisiting the restricted growth function genetic algorithm for grouping problems. Evolutionary Computation 19(4), pp. 693-704. (10.1162/EVCO_a_00040)

### 2010

- Song, X.et al. 2010. A worst case analysis of a dynamic programming-based heuristic algorithm for 2D unconstrained guillotine cutting. European Journal of Operational Research 202(2), pp. 368-378. (10.1016/j.ejor.2009.05.047)

### 2009

- McCollum, B.et al. 2009. Setting the Research Agenda in Automated Timetabling: The Second International Timetabling Competition. INFORMS Journal on Computing 22(1), pp. 120-130. (10.1287/ijoc.1090.0320)
- Lewis, R. 2009. A general-purpose hill-climbing method for order independent minimum grouping problems: A case study in graph colouring and bin packing. Computers & Operations Research 36(7), pp. 2295-2310. (10.1016/j.cor.2008.09.004)

### 2007

- Lewis, R., Paechter, B. and McCollum, B. 2007. Post enrolment based course timetabling: a description of the problem model used for track two of the second International Timetabling Competition. Working paper. Cardiff: Cardiff University.
- Lewis, R. and Paechter, B. 2007. Finding feasible timetables using group-based operators. IEEE Transactions on Evolutionary Computation 11(3), pp. 397-413. (10.1109/TEVC.2006.885162)
- Lewis, R. 2007. A survey of metaheuristic-based techniques for university timetabling problems. OR Spectrum 30(1), pp. 167-190. (10.1007/s00291-007-0097-0)
- Lewis, R. 2007. Metaheuristics can solve sudoku puzzles. Journal of Heuristics 13(4), pp. 387-401. (10.1007/s10732-007-9012-8)
- Lewis, R. 2007. On the combination of constraint programming and stochastic search: the Sudoku case. In: Hybrid Metaheuristics. Lecture Notes in Computer Science Vol. 4771. Springer, pp. 96-107., (10.1007/978-3-540-75514-2_8)
- Lewis, R., Paechter, B. and Rossi-Doria, O. 2007. Metaheuristics for university course timetabling. In: Dahal, K. P., Tan, K. C. and Cowling, P. I. eds. Evolutionary Scheduling. Studies in Computational Intelligence Vol. 49. Springer, pp. 237-272., (10.1007/978-3-540-48584-1_9)

### 2005

- Lewis, R. and Paechter, B. 2005. Application of the grouping genetic algorithm to university course timetabling. Lecture Notes in Computer Science 3448, pp. 144-153. (10.1007/978-3-540-31996-2_14)

## Teaching

### Undergraduate

- MA2760 Mathematical Investigations in Python
- MA3602 Algorithms and Heuristics

### Postgraduate

- MAT002 Statistical Methods

Rhyd Lewis's research interests include:

- Algorithmic graph theory;
- Graph colouring (including vertex colouring, edge colouring and happy colouring) -- see also his book on this topic;
- The application and analysis of metaheuristic and integer programming algorithms;
- Operating theatre scheduling;
- School bus routing;
- Automated timetabling (course and exam) and related problems;
- Grouping and partitioning problems;
- Sports scheduling;
- Solving sudoku problems with metaheuristics;
- Bin-packing, trapezoid (trapezium) packing, and the equal-piles problem;
- Vehicle routing and arc routing, particularly dynamic variants of the problem;

Find out more about his research and download resources at his personal website.

### Research group

## Supervision

I am interested in supervising PhD students in the areas of:

- Combinatorial optimisation
- Algorithmic graph theory
- Graph colouring;
- Packing, scheduling, and timetabling problems
- Routing problems

### Current supervision

## Asyl Hawa

Research student

## Monique Sciortino

Research student

### Past projects

Previous PhD projects:

- Bradley Hardy: Thesis Title:
*"Heuristic methods for colouring dynamic random graphs"* - Penny Holborn: Thesis Title: "
*Dynamic vehicle routing problems with pickups, deliveries and time windows*" - Matthew John: Thesis Title: "
*Metaheuristics for designing efficient routes and schedules for urban transportation networks*" - Elizabeth Rowse: Thesis Title: "
*Robust optimisation of operating theatre schedules*" - Wasin Padungwech: Thesis Title:
*"Heuristic algorithms for dynamic capacitated arc routing"* - Lisa Taylor: Thesis Title: "
*Post-enrolment based course timetabling*"