Publications

Unimodal Probability Distributions for Deep Ordinal Classification
Christopher Beckham
Christopher Pal
Probability distributions produced by the cross-entropy loss for ordinal classification problems can possess undesired properties. We propos… (see more)e a straightforward technique to constrain discrete ordinal probability distributions to be unimodal via a combination of the Poisson probability mass function and the softmax nonlinearity. We evaluate this approach on two large ordinal image datasets and obtain promising results.
2017-07-16
Proceedings of the 34th International Conference on Machine Learning (published)
proceedings.mlr.press
proceedings.mlr.press
APEX_SCOPE: A graphical user interface for visualization of multi-modal data in inter-disciplinary studies.
Lara J. Kanbar
Wissam Shalish
Doina Precup
Karen A. Brown
Guilherme M. Sant'Anna
Robert E. Kearney
2017-07-10
2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) (published)
doi.org
A Semi-Markov Chain Approach to Modeling Respiratory Patterns Prior to Extubation in Preterm Infants
Charles C. Onu
Lara J. Kanbar
Wissam Shalish
Karen A. Brown
Guilherme M. Sant'Anna
Robert E. Kearney
Doina Precup
After birth, extremely preterm infants often require specialized respiratory management in the form of invasive mechanical ventilation (IMV)… (see more). Protracted IMV is associated with detrimental outcomes and morbidities. Premature extubation, on the other hand, would necessitate reintubation which is risky, technically challenging and could further lead to lung injury or disease. We present an approach to modeling respiratory patterns of infants who succeeded extubation and those who required reintubation which relies on Markov models. We compare the use of traditional Markov chains to semi-Markov models which emphasize cross-pattern transitions and timing information, and to multi-chain Markov models which can concisely represent non-stationarity in respiratory behavior over time. The models we developed expose specific, unique similarities as well as vital differences between the two populations.
2017-07-10
2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) (published)
doi.org
arxiv.org
Multiscale sequence modeling with a learned dictionary
Bart Van Merriënboer
Amartya Sanyal
Hugo Larochelle
Yoshua Bengio
We propose a generalization of neural network sequence models. Instead of predicting one symbol at a time, our multi-scale model makes predi… (see more)ctions over multiple, potentially overlapping multi-symbol tokens. A variation of the byte-pair encoding (BPE) compression algorithm is used to learn the dictionary of tokens that the model is trained with. When applied to language modelling, our model has the flexibility of character-level models while maintaining many of the performance benefits of word-level models. Our experiments show that this model performs better than a regular LSTM on language modeling tasks, especially for smaller models.
2017-07-02
ArXiv (preprint)
arxiv.org
arxiv.org
Detecting Large Concept Extensions for Conceptual Analysis
L. Chartrand
Jackie CK Cheung
Mohamed Bouguessa
2017-07-01
Machine Learning and Data Mining in Pattern Recognition (published)
doi.org
arxiv.org
Variance Regularizing Adversarial Learning
Karan Grewal
R Devon Hjelm
Yoshua Bengio
We study how, in generative adversarial networks, variance in the discriminator's output affects the generator's ability to learn the data d… (see more)istribution. In particular, we contrast the results from various well-known techniques for training GANs when the discriminator is near-optimal and updated multiple times per update to the generator. As an alternative, we propose an additional method to train GANs by explicitly modeling the discriminator's output as a bi-modal Gaussian distribution over the real/fake indicator variables. In order to do this, we train the Gaussian classifier to match the target bi-modal distribution implicitly through meta-adversarial training. We observe that our new method, when trained together with a strong discriminator, provides meaningful, non-vanishing gradients.
2017-07-01
ArXiv (preprint)
openreview.net
openreview.net
Towards an Automatic Turing Test: Learning to Evaluate Dialogue Responses
Ryan Lowe
Michael Noseworthy
Iulian V. Serban
Nicolas A.-Gontier
Yoshua Bengio
Joelle Pineau
Automatically evaluating the quality of dialogue responses for unstructured domains is a challenging problem. Unfortunately, existing automa… (see more)tic evaluation metrics are biased and correlate very poorly with human judgements of response quality. Yet having an accurate automatic evaluation procedure is crucial for dialogue research, as it allows rapid prototyping and testing of new models with fewer expensive human evaluations. In response to this challenge, we formulate automatic dialogue evaluation as a learning problem. We present an evaluation model (ADEM) that learns to predict human-like scores to input responses, using a new dataset of human response scores. We show that the ADEM model's predictions correlate significantly, and at a level much higher than word-overlap metrics such as BLEU, with human judgements at both the utterance and system-level. We also show that ADEM can generalize to evaluating dialogue models unseen during training, an important step for automatic dialogue evaluation.
2017-06-30
Annual Meeting of the Association for Computational Linguistics (published)
doi.org
arxiv.org
Towards more hardware-friendly deep learning
Yoshua Bengio
2017-06-23
TiML '17 (published)
doi.org
Reproducibility of Benchmarked Deep Reinforcement Learning Tasks for Continuous Control
Riashat Islam
Peter Henderson
Maziar Gomrokchi
Doina Precup
Policy gradient methods in reinforcement learning have become increasingly prevalent for state-of-the-art performance in continuous control … (see more)tasks. Novel methods typically benchmark against a few key algorithms such as deep deterministic policy gradients and trust region policy optimization. As such, it is important to present and use consistent baselines experiments. However, this can be difficult due to general variance in the algorithms, hyper-parameter tuning, and environment stochasticity. We investigate and discuss: the significance of hyper-parameters in policy gradients for continuous control, general variance in the algorithms, and reproducibility of reported results. We provide guidelines on reporting novel results as comparisons against baseline methods such that future researchers can make informed decisions when investigating novel methods.
2017-06-16
ICML.cc/2017/RML (poster)
openreview.net
openreview.net
Time-Varying Mixtures of Markov Chains: An Application to Road Traffic Modeling
Sean Lawlor
Michael G. Rabbat
Time-varying mixture models are useful for representing complex, dynamic distributions. Components in the mixture model can appear and disap… (see more)pear, and persisting components can evolve. This allows great flexibility in streaming data applications where the model can be adjusted as new data arrives. Fitting a mixture model with computational guarantees which can meet real-time requirements is challenging with existing algorithms, especially when the model order can vary with time. Existing approximate inference methods may require multiple restarts to search for a good local solution. Monte-Carlo methods can be used to jointly estimate the model order and model parameters, but when the distribution of each mixand has a high-dimensional parameter space, they suffer from the curse of dimensionality and and from slow convergence. This paper proposes a generative model for time-varying mixture models, tailored for mixtures of discrete-time Markov chains. A novel, deterministic inference procedure is introduced and is shown to be suitable for applications requiring real-time estimation, and the method is guaranteed to converge at each time step. As a motivating application, we model and predict traffic patterns in a transportation network. Experiments illustrate the performance of the scheme and offer insights regarding tuning of the algorithm parameters. The experiments also investigate the predictive power of the proposed model compared to less complex models and demonstrate the superiority of the mixture model approach for prediction of traffic routes in real data.
2017-06-14
IEEE Transactions on Signal Processing (published)
doi.org
Deep Learning for Patient-Specific Kidney Graft Survival Analysis
Margaux Luck
Tristan Sylvain
Heloise Cardinal
Andrea Lodi
Yoshua Bengio
An accurate model of patient-specific kidney graft survival distributions can help to improve shared-decision making in the treatment and ca… (see more)re of patients. In this paper, we propose a deep learning method that directly models the survival function instead of estimating the hazard function to predict survival times for graft patients based on the principle of multi-task learning. By learning to jointly predict the time of the event, and its rank in the cox partial log likelihood framework, our deep learning approach outperforms, in terms of survival time prediction quality and concordance index, other common methods for survival analysis, including the Cox Proportional Hazards model and a network trained on the cox partial log-likelihood.
2017-05-28
ArXiv (preprint)
arxiv.org
arxiv.org
A Sparse Probabilistic Model of User Preference Data
Matthew J. A. Smith
Laurent Charlin
Joelle Pineau
2017-05-15
Canadian Conference on AI (published)
doi.org