Andrei Cristian Nica

OXtal: An All-Atom Diffusion Model for Organic Crystal Structure Prediction

Emily Jin

Andrei Cristian Nica

Mikhail Galkin

Jarrid Rector-Brooks

Kin Long Kelvin Lee

Santiago Miret

Frances H. Arnold

Michael M. Bronstein

Avishek Bose

Alexander Tong

Cheng-Hao Liu

2025-11-30

arXiv (published)

doi.org

arxiv.org

The Paradox of Choice: On the Role of Attention in Hierarchical Reinforcement Learning

Andrei Cristian Nica

Khimya Khetarpal

Doina Precup

Decision-making AI agents are often faced with two important challenges: the depth of the planning horizon, and the branching factor due to … (see more)having many choices. Hierarchical reinforcement learning methods aim to solve the first problem, by providing shortcuts that skip over multiple time steps. To cope with the breadth, it is desirable to restrict the agent's attention at each step to a reasonable number of possible choices. The concept of affordances (Gibson, 1977) suggests that only certain actions are feasible in certain states. In this work, we first characterize "affordances" as a "hard" attention mechanism that strictly limits the available choices of temporally extended options. We then investigate the role of hard versus soft attention in training data collection, abstract value learning in long-horizon tasks, and handling a growing number of choices. To this end, we present an online, model-free algorithm to learn affordances that can be used to further learn subgoal options. Finally, we identify and empirically demonstrate the settings in which the "paradox of choice" arises, i.e. when having fewer but more meaningful choices improves the learning speed and performance of a reinforcement learning agent.

2022-10-19

NeurIPS.cc/2022/Workshop/Attention (poster)

openreview.net

E VALUATING G ENERALIZATION IN GF LOW N ETS FOR M OLECULE D ESIGN

Moksh J. Jain

Cheng-Hao Liu

Michael M. Bronstein

Deep learning bears promise for drug discovery problems such as de novo molecular design. Generating data to train such models is a costly a… (see more)nd time-consuming process, given the need for wet-lab experiments or expensive simulations. This problem is compounded by the notorious data-hungriness of machine learning algorithms. In small molecule generation the recently proposed GFlowNet method has shown good performance in generating diverse high-scoring candidates, and has the interesting advantage of being an off-policy offline method. Finding an appropriate generalization evaluation metric for such models, one predictive of the desired search performance (i.e. finding high-scoring diverse candidates), will help guide online data collection for such an algorithm. In this work, we develop techniques for evaluating GFlowNet performance on a test set, and identify the most promising metric for predicting generalization. We present empirical results on several small-molecule design tasks in drug discovery, for several GFlowNet training setups, and we find a metric strongly correlated with diverse high-scoring batch generation. This metric should be used to identify the best generative model from which to sample batches of molecules to be evaluated.

2022-04-04

ICLR.cc/2022/Workshop/MLDD (poster)

openreview.net