Last updated 17 January 2025.

Journal Articles

Ryan Boldi, Martin Briesch, Dominik Sobania, Alexander Lalejini, Thomas Helmuth, Franz Rothlauf, Charles Ofria, and Lee Spector. Informed Down-Sampled Lexicase Selection: Identifying productive training cases for efficient problem solving. Evolutionary Computation, pages 1-31, March 2024.
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Thomas Helmuth and Peter Kelly. Applying genetic programming to PSB2: the next generation program synthesis benchmark suite. Genetic Programming and Evolvable Machines, 23(3):375-404, September 2022. Special Issue: Highlights of Genetic Programming 2021 Events.
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Thomas Helmuth and Lee Spector. Problem-Solving Benefits of Down-Sampled Lexicase Selection. Artificial Life, pages 1-21, Sept 2021.
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Thomas Helmuth, Edward Pantridge, and Lee Spector. On the importance of specialists for lexicase selection. Genetic Programming and Evolvable Machines, 21(3):349-373, September 2020. Special Issue: Highlights of Genetic Programming 2019 Events.
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William La Cava, Thomas Helmuth, Lee Spector, and Jason H. Moore. A probabilistic and multi-objective analysis of lexicase selection and epsilon-lexicase selection. Evolutionary Computation, 2019.
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Thomas Helmuth, Lee Spector, and James Matheson. Solving uncompromising problems with lexicase selection. IEEE Transactions on Evolutionary Computation, 19(5):630-643, October 2015.
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Peer-Reviewed Conference Publications

Thomas Helmuth, Jayden Fedoroff, Edward Pantridge, and Lee Spector. Facilitating function application in code building genetic programming. In Proceedings of the Genetic and Evolutionary Computation Conference, GECCO '24, page 887–895, Melbourne, Australia, 2024. Association for Computing Machinery.
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Thomas Helmuth, Edward Pantridge, James Gunder Frazier, and Lee Spector. Generational computation reduction in informal counterexample-driven genetic programming. In Mario Giacobini, Bing Xue, and Luca Manzoni, editors, EuroGP 2024: Proceedings of the 27th European Conference on Genetic Programming, volume 14631 of LNCS, pages 21-37, Aberystwyth, Wales, 3-5 April 2024. Springer.
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Ryan Boldi, Ashley Bao, Martin Briesch, Thomas Helmuth, Dominik Sobania, Lee Spector, and Alexander Lalejini. Untangling the effects of down-sampling and selection in genetic programming. In Artificial Life Conference Proceedings, Copenhagen, Denmark, 22-26 July 2024. MIT Press.
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Edward Pantridge and Thomas Helmuth. Solving novel program synthesis problems with genetic programming using parametric polymorphism. In Proceedings of the 2023 Genetic and Evolutionary Computation Conference, GECCO '23, pages 1175-1183, Lisbon, Portugal, 15-19 July 2023. Association for Computing Machinery.
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Edward Pantridge, Thomas Helmuth, and Lee Spector. Functional code building genetic programming. In Proceedings of the 2022 Genetic and Evolutionary Computation Conference, GECCO '22, pages 1000-1008, Boston, USA, 9-13 July 2022. Association for Computing Machinery.
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Thomas Helmuth, Johannes Lengler, and William La Cava. Population diversity leads to short running times of lexicase selection. In Günter Rudolph, Anna V. Kononova, Hernán Aguirre, Pascal Kerschke, Gabriela Ochoa, and Tea Tušar, editors, Parallel Problem Solving from Nature - PPSN XVII, pages 485-498. Springer International Publishing, August 15 2022.
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Thomas Helmuth and Peter Kelly. PSB2: The second program synthesis benchmark suite. In 2021 Genetic and Evolutionary Computation Conference, GECCO '21, Lille, France, 10-14 July 2021. ACM. Nominated, Best Paper Award, Genetic Programming Track.
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Thomas Helmuth and Lee Spector. Explaining and exploiting the advantages of down-sampled lexicase selection. In Artificial Life Conference Proceedings, pages 341-349. MIT Press, 13-18 July 2020.
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Thomas Helmuth, Edward Pantridge, Grace Woolson, and Lee Spector. Genetic source sensitivity and transfer learning in genetic programming. In Artificial Life Conference Proceedings, pages 303-311. MIT Press, 13-18 July 2020.
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Thomas Helmuth, Edward Pantridge, and Lee Spector. Lexicase selection of specialists. In GECCO '19: Proceedings of the Genetic and Evolutionary Computation Conference, pages 1030-1038, Prague, Czech Republic, 13-17 July 2019. ACM. Winner of Best Paper Award, Genetic Programming Track.
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Lia Jundt and Thomas Helmuth. Comparing and combining lexicase selection and novelty search. In GECCO '19: Proceedings of the Genetic and Evolutionary Computation Conference, pages 1047-1055, Prague, Czech Republic, 13-17 July 2019. ACM.
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Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. Program synthesis using uniform mutation by addition and deletion. In GECCO '18: Proceedings of the Genetic and Evolutionary Computation Conference, pages 1127-1134, Kyoto, Japan, 15-19 July 2018. ACM. Winner of Best Paper Award, Genetic Programming Track
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Thomas Helmuth, Nicholas Freitag McPhee, Edward Pantridge, and Lee Spector. Improving generalization of evolved programs through automatic simplification. In Proceedings of the Genetic and Evolutionary Computation Conference, GECCO '17, pages 937-944, Berlin, Germany, 15-19 July 2017. ACM. Nominated, Best Paper Award, Genetic Programming Track.
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Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. The impact of hyperselection on lexicase selection. In Tobias Friedrich, editor, GECCO '16: Proceedings of the 2016 conference on Genetic and Evolutionary Computation Conference, pages 717-724, Denver, USA, 20-24 July 2016. ACM. Nominated, Best Paper Award, Genetic Programming Track.
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Thomas Helmuth and Lee Spector. General program synthesis benchmark suite. In GECCO '15: Proceedings of the 2015 conference on Genetic and Evolutionary Computation Conference, pages 1039-1046, Madrid, Spain, 11-15 July 2015. ACM.
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William La Cava, Thomas Helmuth, Lee Spector, and Kourosh Danai. Genetic programming with epigenetic local search. In GECCO '15: Proceedings of the 2015 on Genetic and Evolutionary Computation Conference, pages 1055-1062, Madrid, Spain, 11-15 July 2015. ACM. Nominated, Best Paper Award, Genetic Programming Track.
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Thomas Helmuth and Lee Spector. Word count as a traditional programming benchmark problem for genetic programming. In GECCO '14: Proceedings of the 2014 conference on Genetic and evolutionary computation, pages 919-926, Vancouver, BC, Canada, 12-16 July 2014. ACM.
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Lee Spector, Kyle Harrington, and Thomas Helmuth. Tag-based modularity in tree-based genetic programming. In GECCO '12: Proceedings of the fourteenth international conference on Genetic and evolutionary computation conference, pages 815-822, Philadelphia, Pennsylvania, USA, 7-11 July 2012. ACM.
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Lee Spector, Brian Martin, Kyle Harrington, and Thomas Helmuth. Tag-based modules in genetic programming. In GECCO '11: Proceedings of the 13th annual conference on Genetic and evolutionary computation, pages 1419-1426, Dublin, Ireland, 12-16 July 2011. ACM.
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Peer-Reviewed Workshop Publications

Hammad Ahmad and Thomas Helmuth. A comparison of semantic-based initialization methods for genetic programming. In GECCO '18: Proceedings of the Genetic and Evolutionary Computation Conference Companion, pages 1878-1881, Kyoto, Japan, 15-19 July 2018. ACM.
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Edward Pantridge, Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. Specialization and elitism in lexicase and tournament selection. In GECCO '18: Proceedings of the Genetic and Evolutionary Computation Conference Companion, pages 1914-1917, Kyoto, Japan, 15-19 July 2018. ACM.
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Edward Pantridge, Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. On the difficulty of benchmarking inductive program synthesis methods. In Proceedings of the Genetic and Evolutionary Computation Conference Companion, GECCO '17, pages 1589-1596, Berlin, Germany, 15-19 July 2017. ACM.
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Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. Effects of lexicase and tournament selection on diversity recovery and maintenance. In GECCO '16 Companion: Proceedings of the Companion Publication of the 2016 Annual Conference on Genetic and Evolutionary Computation, pages 983-990, Denver, Colorado, USA, 20-24 July 2016. ACM.
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Lee Spector, Nicholas Freitag McPhee, Thomas Helmuth, Maggie M. Casale, and Julian Oks. Evolution evolves with autoconstruction. In GECCO '16 Companion: Proceedings of the Companion Publication of the 2016 Annual Conference on Genetic and Evolutionary Computation, pages 1349-1356, Denver, Colorado, USA, 20-24 July 2016. ACM.
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Nicholas Freitag McPhee, Maggie M. Casale, Mitchell Finzel, Thomas Helmuth, and Lee Spector. Visualizing genetic programming ancestries. In GECCO '16 Companion: Proceedings of the Companion Publication of the 2016 Annual Conference on Genetic and Evolutionary Computation, pages 1419-1426, Denver, Colorado, USA, 20-24 July 2016. ACM.
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Pawel Liskowski, Krzysztof Krawiec, Thomas Helmuth, and Lee Spector. Comparison of semantic-aware selection methods in genetic programming. In GECCO 2015 Semantic Methods in Genetic Programming (SMGP'15) Workshop, pages 1301-1307, Madrid, Spain, 11-15 July 2015. ACM.
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Thomas Helmuth and Lee Spector. Evolving a digital multiplier with the PushGP genetic programming system. In GECCO '13 Companion: Proceeding of the fifteenth annual conference companion on Genetic and evolutionary computation conference companion, pages 1627-1634, Amsterdam, The Netherlands, 6-10 July 2013. ACM.
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Thomas Helmuth, Lee Spector, and Brian Martin. Size-based tournaments for node selection. In GECCO 2011 Graduate students workshop, pages 799-802, Dublin, Ireland, 12-16 July 2011. ACM.
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Non-Refereed Workshop Papers

Edward Pantridge and Thomas Helmuth. Code building genetic programming is fast. In Wolfgang Banzhaf, Ting Hu, Alexander Lalejini, and Stephan Winkler, editors, Genetic Programming Theory and Practice XXI, Genetic and Evolutionary Computation, University of Michigan, USA, June 6-8 2024. [ bib ]

Edward Pantridge, Thomas Helmuth, and Lee Spector. Comparison of linear genome representations for software synthesis. In Wolfgang Banzhaf, Erik Goodman, Leigh Sheneman, Leonardo Trujillo, and Bill Worzel, editors, Genetic Programming Theory and Practice XVII, pages 255-274, East Lansing, MI, USA, 16-19 May 2019. Springer.
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Sarah Anne Troise and Thomas Helmuth. Lexicase selection with weighted shuffle. In Wolfgang Banzhaf, Randal S. Olson, William Tozier, and Rick Riolo, editors, Genetic Programming Theory and Practice XV, Genetic and Evolutionary Computation, pages 89-104, University of Michigan in Ann Arbor, USA, May 18-20 2017. Springer.
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Lee Spector, William La Cava, Saul Shanabrook, Thomas Helmuth, and Edward Pantridge. Relaxations of lexicase parent selection. In Wolfgang Banzhaf, Randal S. Olson, William Tozier, and Rick Riolo, editors, Genetic Programming Theory and Practice XV, Genetic and Evolutionary Computation, pages 105-120, University of Michigan in Ann Arbor, USA, May 18-20 2017. Springer.
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Thomas Helmuth, Lee Spector, Nicholas Freitag McPhee, and Saul Shanabrook. Linear genomes for structured programs. In Rick Riolo, Bill Worzel, Brian Goldman, and Bill Tozier, editors, Genetic Programming Theory and Practice XIV, pages 85-100, Ann Arbor, USA, 19-21 May 2016. Springer.
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Nicholas Freitag McPhee, Mitchell D. Finzel, Maggie M. Casale, Thomas Helmuth, and Lee Spector. A detailed analysis of a PushGP run. In Rick Riolo, Bill Worzel, Brian Goldman, and Bill Tozier, editors, Genetic Programming Theory and Practice XIV, pages 65-83, Ann Arbor, USA, 19-21 May 2016. Springer.
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Thomas Helmuth, Nicholas Freitag McPhee, and Lee Spector. Lexicase selection for program synthesis: A diversity analysis. In Genetic Programming Theory and Practice XIII, Genetic and Evolutionary Computation, Ann Arbor, USA, May 2015. Springer.
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Nicholas Freitag McPhee, David Donatucci, and Thomas Helmuth. Using graph databases to explore genetic programming run dynamics. In Genetic Programming Theory and Practice XIII, Genetic and Evolutionary Computation, Ann Arbor, USA, May 2015. Springer.
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Karthik Kannappan, Lee Spector, Moshe Sipper, Thomas Helmuth, William La Cava, Jake Wisdom, and Omri Bernstein. Analyzing a decade of human-competitive (“HUMIE”) winners: What can we learn? In Genetic Programming Theory and Practice XII, Genetic and Evolutionary Computation, pages 149-166, Ann Arbor, USA, 8-10 May 2014. Springer.
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Lee Spector and Thomas Helmuth. Uniform linear transformation with repair and alternation in genetic programming. In Genetic Programming Theory and Practice XI, Genetic and Evolutionary Computation, chapter 8, pages 137-153. Springer, Ann Arbor, USA, 9-11 May 2013.
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Thomas Helmuth and Lee Spector. Evolving SQL queries from examples with developmental genetic programming. In Genetic Programming Theory and Practice X, Genetic and Evolutionary Computation, chapter 1, pages 1-14. Springer, Ann Arbor, USA, 12-14 May 2012.
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Lee Spector, Kyle Harrington, Brian Martin, and Thomas Helmuth. What's in an evolved name? the evolution of modularity via tag-based reference. In Genetic Programming Theory and Practice IX, Genetic and Evolutionary Computation, chapter 1, pages 1-16. Springer, Ann Arbor, USA, 12-14 May 2011.
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Refereed Posters and Poster Papers

Ryan Boldi, Ashley Bao, Martin Briesch, Thomas Helmuth, Dominik Sobania, Lee Spector, and Alexander Lalejini. A comprehensive analysis of Down-sampling for genetic Programming-based program synthesis. In Proceedings of the 2024 Genetic and Evolutionary Computation Conference Companion, GECCO '24 Companion, pages 487-490, New York, NY, USA, 2024. Association for Computing Machinery. [ bib | DOI | Publisher's Site ]

Ryan Boldi, Alexander Lalejini, Thomas Helmuth, and Lee Spector. A static analysis of informed Down-Samples. In Proceedings of the 2023 Genetic and Evolutionary Computation Conference Companion, GECCO '23, pages 531-534, Lisbon, Portugal, 15-19 July 2023. Association for Computing Machinery. [ bib | DOI ]

Anil Kumar Saini, Lee Spector, and Thomas Helmuth. Environments with local scopes for modules in genetic programming. In Proceedings of the 2022 Genetic and Evolutionary Computation Conference Companion, GECCO '22, Boston, USA, July 9-13 2022. ACM. [ bib ]

Li Ding, Ryan Boldi, Thomas Helmuth, and Lee Spector. Going faster and hence further with lexicase selection. In Proceedings of the 2022 Genetic and Evolutionary Computation Conference Companion, GECCO '22, Boston, USA, July 9-13 2022. ACM. [ bib ]

Thomas Helmuth and Amr Abdelhady. Benchmarking parent selection for program synthesis by genetic programming. In Proceedings of the 2020 Genetic and Evolutionary Computation Conference Companion, GECCO '20, pages 237-238. ACM, July 8-12 2020.
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Thomas Helmuth, Lee Spector, and Edward Pantridge. Counterexample-driven genetic programming without formal specifications. In Proceedings of the 2020 Genetic and Evolutionary Computation Conference Companion, GECCO '20, pages 239-240. ACM, July 8-12 2020.
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Thomas Helmuth, Edward Pantridge, Grace Woolson, and Lee Spector. Transfer learning of genetic programming instruction sets. In Proceedings of the 2020 Genetic and Evolutionary Computation Conference Companion, GECCO '20, pages 241-242. ACM, July 8-12 2020.
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Nicholas Freitag McPhee, Thomas Helmuth, and Lee Spector. Using algorithm configuration tools to optimize genetic programming parameters: A case study. In Proceedings of the Genetic and Evolutionary Computation Conference Companion, GECCO '17, pages 243-244, Berlin, Germany, 15-19 July 2017. ACM.
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Nicholas Freitag McPhee, Maggie M. Casale, Mitchell Finzel, Thomas Helmuth, and Lee Spector. Visualizing genetic programming ancestries using graph databases. In Proceedings of the Genetic and Evolutionary Computation Conference Companion, GECCO '17, pages 245-246, Berlin, Germany, 15-19 July 2017. ACM.
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Lee Spector and Thomas Helmuth. Effective simplification of evolved push programs using a simple, stochastic hill-climber. In GECCO Comp '14: Proceedings of the 2014 conference companion on Genetic and evolutionary computation companion, pages 147-148, Vancouver, BC, Canada, 12-16 July 2014. ACM.
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Thomas Helmuth and Lee Spector. Empirical investigation of size-based tournaments for node selection in genetic programming. In GECCO Companion '12: Proceedings of the fourteenth international conference on Genetic and evolutionary computation conference companion, pages 1485-1486, Philadelphia, Pennsylvania, USA, 7-11 July 2012. ACM.
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Lee Spector, Thomas Helmuth, and Kyle Harrington. Fecundity and selectivity in evolutionary computation. In Proceedings of the 13th Annual Conference Companion on Genetic and Evolutionary Computation, GECCO '11, pages 129-130, Dublin, Ireland, 12-16 July 2011. ACM.
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Tutorials with Published Slides

Thomas Helmuth and Bill La Cava. Lexicase selection. In Proceedings of the 2021 Genetic and Evolutionary Computation Conference Companion, GECCO '21. ACM, July 10-14 2021.
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Dissertation and Technical Reports

Thomas Helmuth. General Program Synthesis from Examples Using Genetic Programming with Parent Selection Based on Random Lexicographic Orderings of Test Cases. PhD thesis. UM-CS-PhD-2015-005, College of Information and Computer Sciences, University of Massachusetts Amherst, USA, September 2015.
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Thomas Helmuth and Lee Spector. Detailed problem descriptions for general program synthesis benchmark suite. Technical Report UM-CS-2015-006, Computer Science, University of Massachusetts Amherst, June 2015.
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