Dimitrios Letsios


Welcome to my personal webpage! My name is Dimitrios Letsios and I am a lecturer (assistant professor) in the Department of Informatics at King's College London and a member of the Algorithms and Data Analysis Group. The foundations of my research are in algorithms and computational optimization, especially at their intersection with data science and artificial intelligence. Motivating applications include energy management in computer systems, fleet management in transportations, and optimization of manufacturing processes. You can find my CV here.


Research Interests

  • Discrete Optimization (Approximation Algorithms, Mixed-Integer Linear Programming)
  • Optimization under Uncertainty (Data-Driven and Robust Optimization)
  • Scheduling and Graph Problems
  • Energy-Efficient Computing, Efficient Big Data Processing
  • Optimization Problems for Process Engineering
  • Explainable Artificial Intelligence

Employment, Visits and Studies

  • Lecturer. Algorithms and Data Analysis Group. King's College London (UK). September 2019 - Present.
  • Postdoctoral Research Associate. Computational Optimisation Group. Imperial College London (UK). July 2016 - August 2019.
  • Teaching and Research Assistant. Combinatorics, Optimization, and Algorithms for Telecommunications Group. INRIA Sophia Antipolis - Méditerranée and Université Nice - Sophia Antipolis (France). September 2015 - July 2016.
  • Postdoctoral Researcher. Chair of Theoretical Computer Science. Technische Universität München (Germany). June 2014 - July 2015.
  • Teaching and Research Assistant. Operational Research Group. Université Pierre et Marie Curie (France). September 2013 - May 2014.
  • Visiting Researcher. University of Pittsburgh (USA). November 2010 - December 2010.
  • Ph.D. in Computer Science, Université d'Evry Val d'Essonne (France), February 2010 - October 2013.
  • M.Sc. in Computer Science, Athens University of Economics and Business (Greece), October 2008 - January 2010.
  • B.Sc. in Informatics, Athens University of Economics and Business (Greece), September 2004 - September 2008.

Publications


International Refereed Journals

  • D. Letsios, J. T. Bradley, S. G, R. Misener, N. Page. Approximate and Robust Bounded Job Start Scheduling for Royal Mail Delivery Offices. Journal of Scheduling , (accepted).    
  • D. Letsios, M. Mistry, R. Misener. Exact Lexicographic Scheduling and Approximate Rescheduling. European Journal of Operational Research, (accepted).    
  • M. Mistry, D. Letsios, G. Krennrich, R. M. Lee, R. Misener. Mixed-Integer Convex Nonlinear Optimization with Gradient-Boosted Trees Embedded. INFORMS Journal on Computing, (accepted).    
  • D. Letsios, R. Baltean-Lugojan, F. Ceccon, M. Mistry, J. Wiebe, R. Misener. Approximation Algorithms for Process Systems Engineering. Computers and Chemical Engineering 132, 106599, 2020.    
  • E. Angel, E.Bampis, F. Kacem, D. Letsios. Speed Scaling on Parallel Processors with Migration. Journal of Combinatorial Optimization 37(4), p. 1266-1282, 2019.    
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. Computers and Chemical Engineering 113, p.57-85, 2018.    
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, M. Sviridenko. Energy-Efficient Scheduling and Routing via Randomized Rounding. Journal of Scheduling 21(1), p.35-51, 2018.    
  • S. Albers, E. Bampis, D. Letsios, G. Lucarelli, R. Stotz. Scheduling on Power-Heterogeneous Processors. Information and Computation 257, p. 22-33, 2017.    
  • E. Angel, E. Bampis, V. Chau, D. Letsios. Throughput Maximization for Speed-Scaling with Agreeable Deadlines. Journal of Scheduling 19(6), p. 619-625, 2016.    
  • E. Bampis, D. Letsios, I. Milis, G. Zois. Speed Scaling for Maximum Lateness. Theory of Computing Systems 58(2), p. 304-321, 2016.    
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, I. Nemparis. From Preemptive to Non-preemptive Speed-Scaling Scheduling. Discrete Applied Mathematics 181, p. 11-20, 2015.    
  • E. Bampis, D. Letsios, G. Lucarelli. Green Scheduling, Flows and Matchings. Theoretical Computer Science 579, p. 126-136, 2015.    
  • N. Barcelo, D. Cole, D. Letsios, M. Nugent, K. Pruhs. Optimal Energy Trade-off Schedules. Journal of Sustainable Computing: Informatics and Systems 3(3), p. 207-217, 2013.    
  • E. Bampis, D. Letsios, G. Lucarelli, V. Markakis, I. Milis. On Multiprocessor Temperature-Aware Scheduling Problems. Journal of Scheduling 16(5), p. 529-538, 2013.    

International Refereed Conferences with Proceedings

  • K. Cyras, A. Karamlou, M. Lee, D. Letsios, R. Misener, F. Toni. AI-assisted Schedule Explainer for Nurse Rostering. International Conference on Autonomous Agents and Multi-agent Systems (AAMAS), p. 2101-2103, 2020. Best innovative demonstration award.    
  • J. Bradley, D. Letsios, R. Misener, N. Page. Approximating Bounded Job Start Scheduling with Application in Royal Mail Deliveries under Uncertainty. International Conference on Combinatorial Optimization and Applications (COCOA), p. 69-81, 2019.    
  • K. Cyras, D. Letsios, R. Misener, F. Toni. Argumentation for Explainable Scheduling. AAAI Conference on Artificial Intelligence (AAAI), p. 2752-2759, 2019.  
  • J.C. Bermond, N. Cohen, D. Coudert, D. Letsios, I. Milis, S. Perennes, V. Zissimopoulos. Bin Packing with Colocations. Workshop on Approximation and Online Algorithms (WAOA) , p. 41-54, LNCS 10138, Springer, 2016.    
  • S. Albers, E. Bampis, D. Letsios, G. Lucarelli, R.Stotz. Scheduling on Power-Heterogeneous Processors. Latin American Theoretical Informatics Symposium (LATIN) , p. 41-54, LNCS 9644, Springer, 2016.    
  • E. Bampis, D. Letsios, G. Lucarelli. Speed Scaling with No Preemptions. International Symposium on Algorithms and Computation (ISAAC) , p. 259-269, LNCS 8889, Springer, 2014.    
  • E. Bampis, V. Chau, D. Letsios, G. Lucarelli, I. Milis, G. Zois. Energy Efficient Scheduling of MapReduce Jobs. International European Conference on Parallel Processing (Euro-Par), p. 198-209, LNCS 8632, Springer, 2014.    
  • E. Bampis, D. Letsios, G. Lucarelli. A Note on Multiprocessor Speed Scaling with Precedence Constraints. ACM Symposium on Parallelism in Algorithms and Architectures (SPAA), p. 138-142, ACM, 2014.    
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, M. Sviridenko. Energy Efficient Scheduling and Routing via Randomized Rounding. Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS) , p. 449-460, LIPIcs 24, Schloss Dagstuhl, 2014.    
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, I. Nemparis. From Preemptive to Non-preemptive Speed-Scaling Scheduling. International Computing and Combinatorics Conference (COCOON), p. 134-146, LNCS 7936, Springer, 2013.    
  • E. Bampis, V. Chau, D. Letsios, G. Lucarelli, I. Milis. Energy Minimization via a Primal-Dual Algorithm for a Convex Program. International Symposium on Experimental Algorithms (SEA), p. 366-377, LNCS 7933, Springer, 2013.    
  • E. Angel, E. Bampis, V. Chau, D. Letsios. Throughput Maximization for Speed-Scaling with Agreeable Deadlines. Conference on Theory and Applications of Models of Computation (TAMC) , p. 10-19, LNCS 7876, Springer, 2013.    
  • E. Bampis, D. Letsios, G. Lucarelli. Green Scheduling, Flows and Matchings. International Symposium on Algorithms and Computation (ISAAC), p. 106-115, LNCS 7676, Springer, 2012.    
  • E. Angel, E. Bampis, F. Kacem, D. Letsios. Speed Scaling on Parallel Processors with Migration. International European Conference on Parallel Processing (Euro-Par) , p. 128-140, LNCS 7484, Springer, 2012.    
  • E. Bampis, D. Letsios, I. Milis, G. Zois. Speed Scaling for Maximum Lateness. International Computing and Combinatorics Conference (COCOON), p. 25-36, LNCS 7434, Springer, 2012.    
  • N. Barcelo, D. Cole, D. Letsios, M. Nugent, K. Pruhs. Optimal Energy Trade-off Schedules. International Green Computing Conference (IGCC) , p. 1-10, IEEE, 2012.    
  • E. Bampis, D. Letsios, G. Lucarelli, V. Markakis, I. Milis. On Multiprocessor Temperature-Aware Scheduling Problems. Joint Conference of International Frontiers of Algorithmics Workshop and International Conference on Algorithmic Aspects of Information and Management (FAW-AAIM), p. 149-160, LNCS 7285, Springer, 2012.    

Conferences / Workshops with Abstracts

  • D. Letsios, R. Misener. Exact Lexicographic Scheduling and Approximate Rescheduling. INFORMS Annual Meeting , 2018.
  • D. Letsios, G. Kouyialis, R. Misener. Approximation Algorithms for Process Systems Engineering. European Symposium on Computer Aided Process Engineering (ESCAPE) , volume 43, p. 565-566, 2018.
  • D. Letsios, R. Misener. Exact Lexicographic Scheduling and Approximate Rescheduling. International Symposium on Mathematical Programming (ISMP) , 2018.
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. IMA Conference on Numerical Linear Algebra and Optimization , 2018.
  • D. Letsios, R. Misener. On Exact Lexicographic Optimization and Approximate Recovery Strategies in Two-Stage Robust Makespan Scheduling. New Challenges in Scheduling Theory Workshop, Aussois, 2018.
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF) , 2018.
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. Research Associate Symposium (RA Symposium), Department of Computing, Imperial College London , 2017. Awarded 2nd prize for presentation. .
  • D. Letsios, R. Misener. Lexicographic Optimization for Rescheduling. IMA and OR Society Conference on Mathematics of Operational Research (IMA-OR) , 2017.
  • S. Albers, E. Bampis, D. Letsios, G. Lucarelli, R. Stotz. Scheduling on Power-Heterogeneous Processors. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF) , 2016.
  • E. Bampis, D. Letsios, G. Lucarelli. Multiprocessor Speed Scaling with Precedence Constraints. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF) , 2015.
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, M. Sviridenko. Energy Efficient Scheduling and Routing via Randomized Rounding. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF) , 2014.
  • E. Bampis, A. Kononov, D. Letsios, G. Lucarelli, M. Sviridenko. Energy Efficient Scheduling and Routing via Randomized Rounding. Workshop on Models and Algorithms for Planning and Scheduling (MAPSP) , 2013.
  • E. Bampis, D. Letsios, G. Lucarelli. Ordonnancement, Flots et Couplages Verts. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF), 2013 .
  • E. Angel, E. Bampis, F. Kacem, D. Letsios. Ordonnancement des Tâches avec Migration et Minimisation de l'Energie Consommée. Congrès Annuel de la Société Francaise de Recherche Opérationelle et d'Aide à la Décision (ROADEF) , 2012.

Posters

  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. SIAM IKIE Meeting, 2018. G. Kouyialis awarded best poster award.
  • L. G. Papageorgiou, V. Dua, P. Parpas, W. Wieseman, R. Misener, E. N. Pistikopoulos, A. Aguirre, V. Charitopoulos, J. Silvente, D. Letsios. Uncertainty-Aware Planning and Scheduling in the Process Industries. CPSE Annual Industrial Consortium Meeting, 2017.
  • M. Mistry, D. Letsios, R. Misener, G. Krennrich, R. M. Lee. Optimization with Gradient-Boosted Trees and Risk Control. CPSE Annual Industrial Consortium Meeting, 2017.
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network Design. CPSE Annual Industrial Consortium Meeting, 2017. G. Kouyialis awarded 2nd prize for poster presentation.
  • D. Letsios, G. Kouyialis, R. Misener. Heuristics with Performance Guarantees for the Minimum Number of Matches in Heat Recovery Network Design. 2nd PSE@ResearchDayUK, 2017. G. Kouyialis awarded best poster prize.
  • L. G. Papageorgiou, V. Dua, P. Parpas, W. Wieseman, R. Misener, E. N. Pistikopoulos, A. Aguirre, V. Charitopoulos, J. Silvente, D. Letsios. Uncertainty-Aware Planning and Scheduling in the Process Industries. CPSE Annual Industrial Consortium Meeting, 2016.

Teaching

King's College London

  • Data Mining. M.Sc. Data Science, M.Sc. Artificial Intelligence, M.Sc. Urban Informatics. Spring 2021, Spring 2020.

Imperial College London

  • Computational Optimization. M.Sc. Computing. Fall 2018.
  • Machine Learning. M.Sc. Business Analytics. Fall 2018.

Université Nice - Sophia Antipolis

  • Introduction to Computer Science. L1 Informatique. Fall 2015.
  • Introduction to Programming with Python. L1 Informatique. Fall 2015, Spring 2016.
  • Introduction to Web Programming with HTML and CSS. L1 Informatique. Fall 2015.
  • Data Structures with Python. L2 Informatique. Fall 2015.
  • Object-Oriented Programming with Java. L3 Informatique. Fall 2015.
  • Probabilities and Statistics. L3 and M1 Miage. Spring 2016.

Technische Universität München

  • Randomized Algorithms. M.Sc. Informatics. Fall 2014.
  • Online and Approximation Algorithms. M.Sc. Informatics. Spring 2015.

Université Pierre et Marie Curie

  • Introduction to Programming with C. L1 Polytech. Spring 2014.
  • Data Structures with C. L2 Polytech. Fall 2013.
  • Special Topics on Algorithms. L3 Informatique and M1 IAD. Spring 2014.

Université d'Evry Val d'Essonne

  • Introduction to Programming with C. L2 Chimie. Fall 2010, Fall 2011.
  • Introduction to Programming with Java. L1 Informatique. Fall 2012.
  • Introduction to Algorithms. L3 Informatique. Spring 2012, Spring 2013.
  • Graph Algorithms. L3 Informatique. Spring 2011, Spring 2012, Spring 2013.
  • Mathematical Programming. M1 MOPS. Spring 2011, Spring 2012.
  • Operational Research. M1 MOPS. Spring 2013.

Professional Service

Program Committees

  • AAAI Explainable Agency in Artificial Intelligence Workshop (XAI-AAAI 2021)
  • AAAI Conference on Artificial Intelligence (AAAI 2021)
  • International Joint Conference on Artificial Intelligence - Pacific Rim International Conference on Artificial Intelligence (IJCAI - PRICAI 2020)
  • International Workshop on Combinatorial Algorithms (IWOCA 2020)
  • IJCAI Workshop on Explainable Artificial Intelligence (XAI 2019)
  • International Parallel and Distributed Processing Symposium (IPDPS 2019)
  • International Conference on Parallel Processing (ICPP 2017)

Organizing Committees

  • London Stringology Days and London Algorithmic Workshop (LSD&LAW 2020) [Co-Chair]  
  • ICALP Satellite Workshop on Approximation, Parameterized and Exact Algorithms (APEX 2013)

Journal External Reviewing

  • Algorithmica, Computational Optimization and Applications (COAP), Journal of Global Optimization (JOGO), Journal of Parallel and Distributed Computing (JPDC), Journal of Scheduling (JOSH), International Journal of Production Research, Omega - The International Journal of Management Science, Operational Research - An International Journal (ORIJ), Parallel Processing Letters (PPL), RAIRO Operations Research, Theoretical Computer Science (TCS), IEEE Transactions on Parallel and Distributed Systems (TPDS)

Conference External Reviewing

  • IPCO 2020, IPDPS 2020, IPCO 2019, SPAA 2018, ACC 2017, CIAC 2017, COCOA 2017, Euro-Par 2017, CIAC 2016, COCOA 2016, DOOR 2016, ICALP 2016, ISCO 2016, SODA 2016, ESA 2015, Euro-Par 2015, SEA 2015, SODA 2015, SOFSEM 2015, WADS 2015, CCGrid 2014, IPDPS 2014, ISCO 2014, WAOA 2014, CIAC 2013, ICALP 2013, IPDPS 2013, Euro-Par 2012, ISCO 2012, IPDPS 2012, SEA 2012, WAOA 2012, WAOA 2011, WAOA 2010



Students

Office Hours

  • Thursdays 10am-12pm. Teams link:

Prospective Students

  • A PhD studentship on Optimization Models and Algorithms for Resource Allocation Problems with Machine Learning Predictions is currently available to be funded by the Faculty of Natural and Mathematical Sciences of King's College London.
  • A PhD studentship on Data-Driven and Explainable Discrete Optimization for Effective Transportation in Healthcare is currently available to be funded by the UKRI Centre for Doctoral Training in Safe and Trusted Artificial Intelligence.
  • Successful applicants are expected to: (i) have obtained or be close to obtaining an M.Sc. degree in computer science, mathematics, engineering, or other relevant discipline, (ii) demonstrate their interest and skills on algorithms, data science, and artificial intelligence (analytical thinking with mathematical rigor will be needed), (iii) have reasonable programming skills (Python coding will be needed), and (iv) have good communication skills in English. Prior experience on integer programming and approximation / online algorithms should be particularly useful.
  • Candidates interested in these positions are invited to contact me with their CV and a brief statement of interest (no more than 1-2 paragraphs). Because the application process for PhD positions at King's requires a short research proposal (e.g. 3-4 pages), you may want to request advice about this with your first contact.

PhD Students

  • Anna Collins (Nov 2019 - present)

MSc Students

  • Yuhui Cheng (Jan - Sep 2020)
  • Zixi He (Jan - Sep 2020)
  • Athanasios Liaskas (Jan - Jun 2020)
  • Kaiyue Liu (Jan - Sep 2020)
  • Yixuan Shen (Jan - Sep 2020)
  • Ying Zhang (Jan - Sep 2020)

Contact Details

  dimitrios.letsios@kcl.ac.uk
  Office N5.12, Bush House, 30 Aldwych, London, WC2B 4BG