Publications

Development of a hydrated electron dosimeter for radiotherapy applications: A proof of concept.
Julien Mégrourèche
H. Bekerat
Jingyi Bian
Alaina Bui
Jack C Sankey
Lilian Childress
Shirin A. Enger
BACKGROUND Hydrated electrons, which are short-lived products of radiolysis in water, increase the optical absorption of water, providing a … (voir plus)pathway toward near-tissue-equivalent clinical radiation dosimeters. This has been demonstrated in high-dose-per-pulse radiochemistry research, but, owing to the weak absorption signal, its application in existing low-dose-per-pulse radiotherapy provided by clinical linear accelerators (linacs) has yet to be investigated. PURPOSE The aims of this study were to measure the optical absorption associated with hydrated electrons produced by clinical linacs and to assess the suitability of the technique for radiotherapy (⩽ 1 cGy per pulse) applications. METHODS 40 mW of 660-nm laser light was sent five passes through deionized water contained in a 10 × 4 ×
2023-06-19
Medical Physics (publié)
doi.org
An Empirical Study of the Effectiveness of Using a Replay Buffer on Mode Discovery in GFlowNets
Nikhil Murali Vemgal
Elaine Lau
Doina Precup
Reinforcement Learning (RL) algorithms aim to learn an optimal policy by iteratively sampling actions to learn how to maximize the total exp… (voir plus)ected return,
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
doi.org
openreview.net
Exploring Exchangeable Dataset Amortization for Bayesian Posterior Inference
Sarthak Mittal
Niels Leif Bracher
Guillaume Lajoie
Priyank Jaini
Marcus A Brubaker
Bayesian inference provides a natural way of incorporating uncertainties and different underlying theories when making predictions or analyz… (voir plus)ing complex systems. However, it requires computationally expensive routines for approximation, which have to be re-run when new data is observed and are thus infeasible to efficiently scale and reuse. In this work, we look at the problem from the perspective of amortized inference to obtain posterior parameter distributions for known probabilistic models. We propose a neural network-based approach that can handle exchangeable observations and amortize over datasets to convert the problem of Bayesian posterior inference into a single forward pass of a network. Our empirical analyses explore various design choices for amortized inference by comparing: (a) our proposed variational objective with forward KL minimization, (b) permutation-invariant architectures like Transformers and DeepSets, and (c) parameterizations of posterior families like diagonal Gaussian and Normalizing Flows. Through our experiments, we successfully apply amortization techniques to estimate the posterior distributions for different domains solely through inference.
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
openreview.net
openreview.net
GFlowNets for Causal Discovery: an Overview
Dragos Cristian Manta
Edward J Hu
Yoshua Bengio
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
openreview.net
openreview.net
Green Federated Learning
Ashkan Yousefpour
Shen Guo
Ashish Shenoy
Sayan Ghosh
Pierre Stock
Kiwan Maeng
Schalk-Willem Kruger
Michael Rabbat
Carole-Jean Wu
Ilya Mironov
2023-06-19
ICML.cc/2023/Workshop/FL (publié)
openreview.net
openreview.net
Identifiability of Discretized Latent Coordinate Systems via Density Landmarks Detection
Vitória Barin-Pacela
Kartik Ahuja
Simon Lacoste-Julien
Pascal Vincent
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
openreview.net
openreview.net
Identifiability of Discretized Latent Coordinate Systems via Density Landmarks Detection
Vitória Barin-Pacela
Kartik Ahuja
Simon Lacoste-Julien
Pascal Vincent
Disentanglement aims to recover meaningful latent ground-truth factors from only the observed distribution. Identifiability provides the the… (voir plus)oretical grounding for disentanglement to be well-founded. Unfortunately, unsupervised identifiability of independent latent factors is a theoretically proven impossibility in the i.i.d. setting under a general nonlinear smooth map from factors to observations. In this work, we show that, remarkably, it is possible to recover discretized latent coordinates under a highly generic nonlinear smooth mapping (a diffeomorphism) without any additional inductive bias on the mapping. This is, assuming that latent density has axis-aligned discontinuity landmarks, but without making the unrealistic assumption of statistical independence of the factors. We introduce this novel form of identifiability, termed quantized coordinate identifiability , and provide a comprehensive proof of the recovery of discretized coordinates.
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
doi.org
openreview.net
A Kernel Perspective on Behavioural Metrics for Markov Decision Processes
Pablo Samuel Castro
Tyler Kastner
Prakash Panangaden
Mark Rowland
We present a novel perspective on behavioural metrics for Markov decision processes via the use of positive definite kernels. We define a ne… (voir plus)w metric under this lens that is provably equivalent to the recently introduced MICo distance (Castro et al., 2021). The kernel perspective enables us to provide new theoretical results, including value-function bounds and low-distortion finite-dimensional Euclidean embeddings, which are crucial when using behavioural metrics for reinforcement learning representations. We complement our theory with strong empirical results that demonstrate the effectiveness of these methods in practice.
2023-06-19
TMLR (accepté)
doi.org
openreview.net
Learning to Optimize with Recurrent Hierarchical Transformers
Abhinav Moudgil
Boris Knyazev
Guillaume Lajoie
Eugene Belilovsky
2023-06-19
ICML.cc/2023/Workshop/Frontiers4LCD (publié)
openreview.net
openreview.net
Learning with Learning Awareness using Meta-Values
Tim Cooijmans
Milad Aghajohari
Aaron Courville
2023-06-19
ICML.cc/2023/Workshop/Frontiers4LCD (publié)
openreview.net
openreview.net
Online Dynamic Submodular Optimization
Antoine Lesage-Landry
Julien Pallage
We propose new algorithms with provable performance for online binary optimization subject to general constraints and in dynamic settings. W… (voir plus)e consider the subset of problems in which the objective function is submodular. We propose the online submodular greedy algorithm (OSGA) which solves to optimality an approximation of the previous round loss function to avoid the NP-hardness of the original problem. We extend OSGA to a generic approximation function. We show that OSGA has a dynamic regret bound similar to the tightest bounds in online convex optimization with respect to the time horizon and the cumulative round optimum variation. For instances where no approximation exists or a computationally simpler implementation is desired, we design the online submodular projected gradient descent (OSPGD) by leveraging the Lova\'sz extension. We obtain a regret bound that is akin to the conventional online gradient descent (OGD). Finally, we numerically test our algorithms in two power system applications: fast-timescale demand response and real-time distribution network reconfiguration.
2023-06-19
ArXiv (prépublication)
doi.org
arxiv.org
Pretrained Language Models to Solve Graph Tasks in Natural Language
Frederik Wenkel
Guy Wolf
Boris Knyazev
Pretrained large language models (LLMs) are powerful learners in a variety of language tasks. We explore if LLMs can learn from graph-struct… (voir plus)ured data when the graphs are described using natural language. We explore data augmentation and pretraining specific to the graph domain and show that LLMs such as GPT-2 and GPT-3 are promising alternatives to graph neural networks.
2023-06-19
ICML.cc/2023/Workshop/SPIGM (poster)
openreview.net
openreview.net