Refereed Publications

2019

Procedural Generation of Initial States of Sokoban.
Damaris Bento, Andre G. Pereira, and Levi Lelis.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2019.
[pdf].

Iterative Budgeted Exponential Search.
Malte Helmert, Tor Lattimore, Levi Lelis, Laurent Orseau, and Nathan Sturtevant.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2019.

Evolving Action Abstractions for Real-Time Planning in Extensive-Form Games
Julian Marino, Rubens O. Moraes, Claudio Toledo, and Levi Lelis
In the Proceedings of the Conference on Artificial Intelligence (AAAI), 2019.
[pdf].

Be Inaccurate but don't be Indecisive: How Error Distribution Can Affect User Experience
Rafael Padovani, Lucas N. Ferreira, and Levi Lelis.
In the Proceedings of the Conference on Artificial Intelligence (AAAI), 2019.
[pdf].

2018

Single-Agent Policy Tree Search with Guarantees
Laurent Orseau, Levi Lelis, Tor Lattimore, and Theophane Weber
In the Proceedings of the Conference on Neural Information Processing Systems (NIPS), 2018.
[pdf].

Asymmetric Action Abstractions for Multi-Unit Control in Adversarial Real-Time Games
Rubens O. Moraes and Levi Lelis
In the Proceedings of the Conference on Artificial Intelligence (AAAI), 2018.
[pdf].

Action Abstractions for Combinatorial Multi-Armed Bandit Tree Search
Rubens O. Moraes, Julian Marino, Levi Lelis, and Mario Nascimento
In the Proceedings of the AAAI Conference on AI and Interactive Digital Entertainment (AIIDE), 2018.
[pdf] [video].

Nested-Greedy Search for Adversarial Real-Time Games
Rubens O. Moraes, Julian Marino, and Levi Lelis
In the Proceedings of the AAAI Conference on AI and Interactive Digital Entertainment (AIIDE), 2018.
[pdf] [video].

Procedural Generation of Game Maps with Human-in-the-Loop Algorithms
Levi Lelis, Willian Reis, and Ya'akov (Kobi) Gal
IEEE Transactions on Games 2018.
[pdf].

The First MicroRTS Artificial Intelligence Competition
Santiago Ontanon, Nicolas Barriga, Cleyton Silva, Rubens Moraes, and Levi Lelis
AI Magazine 2018.
[pdf].

2017

Stratified Strategy Selection for Unit Control in Real-Time Strategy Games.
Levi Lelis.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2017.
[pdf].

On Creating Complementary Pattern Databases.
Santiago Franco, Alvaro Torralba, Levi Lelis, and Mike Barley.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2017.
[pdf].

Bardo: Emotion-based Music Recommendation for Tabletop Role-Playing Games.
Rafael Padovani, Lucas N. Ferreira, and Levi Lelis.
In the Proceedings of the AAAI Conference on AI and Interactive Digital Entertainment (AIIDE), 2017.
[pdf].

Understanding Mario: An Evaluation of Design Metrics For Platformers.
Adam Summerville, Julian Marino, Sam Snodgrass, Santiago Ontanon and Levi Lelis.
In Proceedings of the International Conference on the Foundations of Digital Games (FDG) 2017.
[pdf].

Mixed-Initiative Tool to Speed Up Content Creation in Physics-Based Games
Cesar R. F. G. Campos, Walter de O. Sa, Joao Marcos G. Teixeira, and Levi Lelis.
In Proceedings of the SBGames 2017.
[pdf].

2016

A Computational Model based on Symmetry for Generating Visually Pleasing Maps of Platform Games.
Julian Marino and Levi Lelis.
In the Proceedings of the AAAI Conference on AI and Interactive Digital Entertainment (AIIDE), 2016.
[pdf].

Learning to Speed Up Evolutionary Content Generation in Physics-based Puzzle Games.
Leonardo Pereira, Claudio Toledo, Lucas Ferreira, and Levi Lelis.
In the Proceedings of the IEEE International Conference on Tools with Artificial Intelligence (ICTAI), 2016.
[pdf].

Searching with a Corrupted Heuristic.
Levi Lelis, Rick Valenzano, Gabriel Nazar, and Roni Stern.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2016.
[pdf].

Heuristic Subset Selection in Classical Planning.
Levi Lelis, Santiago Franco, Marvin Abisrror, Mike Barley, Sandra Zilles, and Robert Holte.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2016.
[pdf].

What's Hot in Heuristic Search? (Invited Extended Abstract)
Roni Stern and Levi Lelis
In the Proceedings of the Conference on Artificial Intelligence (AAAI) 2016.
[pdf].

Predicting Optimal Solution Costs with Bidirectional Stratified Sampling in Regular Search Spaces.
Levi Lelis, Roni Stern, Shahab Jabbari Arfaee, Sandra Zilles, Ariel Felner, and Robert C. Holte.
Artificial Intelligence, 2016.
[pdf].

2015

An Empirical Evaluation of Evaluation Metrics of Procedurally Generated Mario Levels.
Julian Marino, Willian Reis, and Levi Lelis.
In the Proceedings of the AAAI Conference on AI and Interactive Digital Entertainment (AIIDE), 2015.
[pdf].

Human Computation for Procedural Content Generation in Platform Games.
Willian Reis, Levi Lelis, and Ya'akov (Kobi) Gal.
In the Proceedings of the Conference on Computational Intelligence and Games (CIG), 2015.
[pdf].

Feature Selection as State-Space Search: An Empirical Study in Clustering Problems.
Julian Marino and Levi Lelis.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2015.
[pdf].

Caching in Context-Minimal OR Spaces.
Rina Dechter, Levi Lelis, and Lars Otten.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2015.
[pdf].

Stratified Sampling for Even Workload Partitioning Applied to Single Source Shortest Path Algorithm.
Jeeva Paudel, Levi Lelis, and Jose Nelson Amaral.
In the Proceedings of the Annual International Conf. on Computer Science and Software Engineering (CASCON). 2015.
[pdf].

Stratified Sampling for Even Workload Partitioning Applied to IDA* and Delaunay Algorithms.
Jeeva Paudel, Levi Lelis, and Jose Nelson Amaral.
In the Proceedings of the International Parallel & Distributed Processing Symposium (IPDPS), 2015.
[pdf].

2014

Predicting optimal solution cost with conditional probabilities.
Levi Lelis, Roni Stern, Ariel Felner, Sandra Zilles, and Robert C. Holte.
Annals of Mathematics and Artificial Intelligence, 2014.
[pdf] or [publisher's website for this paper].

Estimating Search Tree Size with Duplicate Detection.
Levi Lelis, Roni Stern, and Nathan Sturtevant.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2014.
[pdf].

Memory-Efficient Tree Size Prediction for Depth-First Search in Graphical Models.
Levi Lelis, Lars Otten, and Rina Dechter.
In the Proceedings of the International Conference on Principles and Practice of Constraint Programming (CP), 2014.
[pdf].

2013

Cluster-and-Conquer: a Paradigm for Solving State-Space Problems.
Levi Lelis.
PhD Dissertation, University of Alberta, 2013.
[pdf].

Active Stratified Sampling with Clustering-Based Type Systems for Predicting the Search Tree Size of Problems with Real-Valued Heuristics.
Levi Lelis.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2013.
[pdf].

Predicting the Size of Depth-First Branch and Bound Search Trees.
Levi Lelis, Lars Otten, and Rina Dechter.
In the Proceedings of the International Joint Conference on Artificial Intelligence (IJCAI) 2013.
[pdf].

Predicting the Size of IDA*'s Search Tree.
Levi Lelis, Sandra Zilles, and Robert C. Holte.
Artificial Intelligence, 2013.
[pdf].

Stratified Tree Search: A Novel Suboptimal Heuristic Search Algorithm.
Levi Lelis, Sandra Zilles, and Robert C. Holte.
In the Proceedings of the Conference on Autonomous Agents and Multiagent Systems (AAMAS) 2013.
[pdf].

2012

Fast and Accurate Predictions of IDA*'s Performance.
Levi Lelis, Sandra Zilles, and Robert C. Holte.
In the Proceedings of the Conference on Artificial Intelligence (AAAI) 2012.
[pdf].

Predicting Optimal Solution Cost with Bidirectional Stratified Sampling.
Levi Lelis, Roni Stern, Ariel Felner, Sandra Zilles, and Robert C. Holte.
In the Proceedings of the International Conference on Automated Planning and Scheduling (ICAPS) 2012.
[pdf].

Learning Heuristic Functions Faster by Using Predicted Solution Costs.
Levi Lelis, Shahab Jabbari Arfaee, Sandra Zilles, and Robert C. Holte.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2012.
[pdf].

Are We There Yet? -- Estimating Search Progress.
Jordan Thayer, Roni Stern, and Levi Lelis.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2012.
[pdf].

2011

Predicting Solution Cost with Conditional Probabilities.
Levi Lelis, Roni Stern, and Shahab Jabbari Arfaee.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2011.
[pdf].

Improved Prediction of IDA*'s Performance via e-Truncation.
Levi Lelis, Sandra Zilles, and Robert C. Holte.
In the Proceedings of the Symposium on Combinatorial Search (SoCS), 2011.
[pdf].

Time Complexity of Iterative-Deepening A*: The Informativeness Pathology (Abstract).
Levi Lelis, Sandra Zilles, and Robert C. Holte.
In AAAI Student Abstract and Poster Section 2011.
[pdf].

2009

Semi-supervised density-based clustering.
Levi Lelis and Joerg Sander.
In the IEEE Proceedings of the International Conference of Data Mining (ICDM) 2009.
[pdf].

2007

Semi-Supervised Learning Applied to Financial Prediction.
Levi Lelis.
Master Dissertation. Department of Electrical Engineering, Federal University of Minas Gerais, Brazil, 128 pages, Technical Report, 2007 (in Portuguese).