After graduating summa cum laude from Universiteit Gent, Belgium in 2014 with an engineering degree (burgerlijk ingenieur) in computer science, I obtained a doctorate in the beginning of 2017 at IDLab, which was supported by a Doctoral Fellowship of the Research Foundation — Flanders (FWO) for fundamental research.

Initially I performed applied research in combinatorial optimization and operations research at the CODeS group, part of KU Leuven, Belgium, in collaboration with ArcelorMittal. Hereafter I worked in the domain of network science, designing experimental routing strategies for computer networks. Later my interests shifted to artificial intelligence and machine learning, which became my true passion.

More specifically I focused on combining deep neural networks with structured prediction. During my doctoral studies, I also acted as a researcher at the R&D institute imec, which allowed me to apply my research to visual perception in autonomous agricultural vehicles, in collaboration with CNH Industrial.

Later as part of my doctoral studies, I investigated exploration strategies for deep reinforcement learning. During this time, I pursued research both at OpenAI and at the Berkeley Artificial Intelligence Research lab (BAIR), part of UC Berkeley, with Pieter Abbeel. This latter stay was supported by a Travel Grant of the FWO.

From 2017 to 2018, I was a research scientist at OpenAI in machine learning with a focus on deep reinforcement learning. I co-organized the Deep Reinforcement Learning Workshop at NIPS 2017/2018 and was involved in the Berkeley Deep RL Bootcamp.

In 2018 I co-founded the San Francisco/Beijing AI lab at Happy Elements where I am currently Head of AI. Our team builds machine learning algorithms and their supporting infrastructure and analytics platforms for online gameplay generation in mobile games, servicing over 100 million unique players each month. A presentation given at the RE-WORK Applied AI Summit can be found here which explains on a high level how our team is applying deep (reinforcement) learning for hyper-personalization.

Learning to learn in deep reinforcement learning (RL), including learning to explore without the use of additional structures. Below a video of a robot learning to grasp from scratch without simulator resets and a robot learning to walk towards targets out of training distribution, using Evolved Policy Gradients (EPG).

Evolved Policy Gradients Advances in Neural Information Processing Systems (NeurIPS), 2018 R. Houthooft, R. Y. Chen, P. Isola, B. C. Stadie, F. Wolski, J. Ho, P. Abbeel |
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Some Considerations on Learning to Explore via Meta-Reinforcement Learning Advances in Neural Information Processing Systems (NeurIPS), 2018 B. C. Stadie, G. Yang, R. Houthooft, X. Chen, Y. Duan, W. Yuhuai, P. Abbeel, I. Sutskever |
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Reinforcement learning (RL) using nonlinear function approximators with a focus on continuous control tasks such as robot locomotion. In particular, the goal is to investigate how to achieve efficient exploration in deep RL through curiosity. This research was performed in collaboration with OpenAI and the Berkeley AI Research lab.

Parameter Space Noise for Exploration International Conference on Learning Representations (ICLR), 2018 M. Plappert, R. Houthooft, P. Dhariwal, S. Sidor, R. Y. Chen, X. Chen, T. Asfour, P. Abbeel, M. Andrychowicz |
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#Exploration: A Study of Count-Based Exploration for Deep Reinforcement Learning Advances in Neural Information Processing Systems (NIPS), 2017 H. Tang, R. Houthooft, D. Foote, A. Stooke, X. Chen, Y. Duan, J. Schulman, F. De Turck, P. Abbeel |
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VIME: Variational Information Maximizing Exploration Advances in Neural Information Processing Systems (NIPS), 2016 R. Houthooft, X. Chen, Y. Duan, J. Schulman, F. De Turck, P. Abbeel |
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Benchmarking Deep Reinforcement Learning for Continuous Control International Conference on Machine Learning (ICML), 2016 Y. Duan, X. Chen, R. Houthooft, J. Schulman, P. Abbeel |
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InfoGAN is a generative adversarial network that also maximizes the mutual information between a small subset of the latent variables and the observation. We derive a lower bound of the mutual information objective that can be optimized efficiently.

InfoGAN: Interpretable Representation Learning by Information Maximizing Generative Adversarial Nets Advances in Neural Information Processing Systems (NIPS), 2016 X. Chen, Y. Duan, R. Houthooft, J. Schulman, I. Sutskever, P. Abbeel |
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As part of an autonomous vehicle project, the goal was to combine structured output prediction and deep learning techniques, with a particular focus on semantic image segmentation. Structural support vector machines (SSVMs) were extended to allow for highly nonlinear factors. This can enhance output coherence of deep predictive models, while still allowing for end-to-end training. Below the architecture of a deep SSVM with convolutional neural factors is pictured.

Integrated Inference and Learning of Neural Factors in Structural Support Vector Machines^{*}Pattern Recognition, vol. 59, 2016 R. Houthooft, F. De Turck |
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^{*} This work is part of an applied research project in collaboration with Case New Holland (CNH) Industrial. As such several methods, models, datasets, and results could not be publicly released due to confidentiality agreements. An addendum to these papers can be found here. Initial vehicle controller patent applications have been filed.

My research originally focused on the development of a novel routing algorithm called * Forest Routing*. Through geometric routing, using a set of graph embeddings in a particular mathematical space, it offers both high scalability and native load balancing behavior. A coherent write-up on the subject can be found in my thesis Adaptive Geometric Routing for the Internet Backbone. Below a demonstration of the developed model is shown.

Optimizing Robustness in Geometric Routing via
Embedding Redundancy and Regeneration Networks, vol. 66, no. 4, 2015 R. Houthooft, S. Sahhaf, W. Tavernier, F. De Turck, D. Colle, M. Pickavet |
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Robust Geometric Forest Routing with Tunable Load Balancing The 34th Annual IEEE International Conference on Computer Communications (INFOCOM), 2015 R. Houthooft, S. Sahhaf, W. Tavernier, F. De Turck, D. Colle, M. Pickavet |
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Fault-Tolerant Greedy Forest Routing for Complex Networks The 6th International Workshop on Reliable Networks Design and Modeling (RNDM), 2014 — best paper award Featured in Global Communications Newsletter May 2015 R. Houthooft, S. Sahhaf, W. Tavernier, F. De Turck, D. Colle, M. Pickavet |
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