Publications

Nifty Assignments
Nick Parlante
Julie Zelenski
Dave Feinberg
Kunal Mishra
Josh Hug
Kevin Wayne
Michael Guerzhoy
Jackie CK Cheung
François Pitt
I suspect that students learn more from our programming assignments than from our much sweated-over lectures, with their slide transitions, … (see more)clip art, and joke attempts. A great assignment is deliberate about where the student hours go, concentrating the student's attention on material that is interesting and useful. The best assignments solve a problem that is topical and entertaining, providing motivation for the whole stack of work. Unfortunately, creating great programming assignments is both time consuming and error prone. The Nifty Assignments special session is all about promoting and sharing the ideas and ready-to-use materials of successful assignments.
2017-03-07
Proceedings of the 2017 ACM SIGCSE Technical Symposium on Computer Science Education (published)
doi.org
Learning-based interactive segmentation using the maximum mean cycle weight formalism
S. Nilufar
D. S. Wang
J. Girgis
C. G. Palii
D. Yang
A. Blais
M. Brand
Doina Precup
T. J. Perkins
The maximum mean cycle weight (MMCW) segmentation framework is a graph-based alternative to approaches such as GraphCut or Markov Random Fie… (see more)lds. It offers time- and space-efficient computation and guaranteed optimality. However, unlike GraphCut or Markov Random Fields, MMCW does not seek to segment the entire image, but rather to find the single best object within the image, according to an objective function encoded by edge weights. Its focus on a single, best object makes MMCW attractive to interactive segmentation settings, where the user indicates which objects are to be segmented. However, a provably correct way of performing interactive segmentation using the MMCW framework has never been established. Further, the question of how to develop a good objective function based on user-provided information has never been addressed. Here, we propose a three-component objective function specifically designed for use with interactive MMCW segmentation. Two of those components, representing object boundary and object interior information, can be learned from a modest amount of user-labelled data, but in a way unique to the MMCW framework. The third component allows us to extend the MMCW framework to the situation of interactive segmentation. Specifically, we show that an appropriate weighted combination of the three components guarantees that the object produced by MMCW segmentation will enclose user-specified pixels that can be chosen interactively. The component weights can either be computed a priori based on image characteristics, or online via an adaptive reweighting scheme. We demonstrate the success of the approach on several microscope image segmentation problems.
2017-02-23
Medical Imaging (published)
doi.org
Char2Wav: End-to-End Speech Synthesis
Jose Sotelo
Soroush Mehri
Kundan Kumar
Joao Felipe Santos
Kyle Kastner
Aaron Courville
Yoshua Bengio
2017-02-16
International Conference on Learning Representations (unknown)
openreview.net
openreview.net
Deep Nets Don't Learn Via Memorization
David Krueger
Nicolas Ballas
Stanislaw Jastrzebski
Devansh Arpit
Maxinder S. Kanwal
Tegan Maharaj
Emmanuel Bengio
Asja Fischer
Aaron Courville
2017-02-16
International Conference on Learning Representations (unknown)
openreview.net
openreview.net
The Option-Critic Architecture
Pierre-Luc Bacon
Jean Harb
Doina Precup
Temporal abstraction is key to scaling up learning and planning in reinforcement learning. While planning with temporally extended actions i… (see more)s well understood, creating such abstractions autonomously from data has remained challenging. We tackle this problem in the framework of options [Sutton, Precup & Singh, 1999; Precup, 2000]. We derive policy gradient theorems for options and propose a new option-critic architecture capable of learning both the internal policies and the termination conditions of options, in tandem with the policy over options, and without the need to provide any additional rewards or subgoals. Experimental results in both discrete and continuous environments showcase the flexibility and efficiency of the framework.
2017-02-12
Proceedings of the AAAI Conference on Artificial Intelligence (published)
doi.org
arxiv.org
A Hierarchical Latent Variable Encoder-Decoder Model for Generating Dialogues
Iulian V. Serban
Alessandro Sordoni
Ryan Lowe
Laurent Charlin
Joelle Pineau
Aaron Courville
Yoshua Bengio
Sequential data often possesses a hierarchical structure with complex dependencies between subsequences, such as found between the utterance… (see more)s in a dialogue. In an effort to model this kind of generative process, we propose a neural network-based generative architecture, with latent stochastic variables that span a variable number of time steps. We apply the proposed model to the task of dialogue response generation and compare it with recent neural network architectures. We evaluate the model performance through automatic evaluation metrics and by carrying out a human evaluation. The experiments demonstrate that our model improves upon recently proposed models and that the latent variables facilitate the generation of long outputs and maintain the context.
2017-02-11
Proceedings of the AAAI Conference on Artificial Intelligence (published)
doi.org
arxiv.org
Multiresolution Recurrent Neural Networks: An Application to Dialogue Response Generation
Iulian V. Serban
Tim Klinger
Gerald Tesauro
Kartik Talamadupula
Bowen Zhou
Yoshua Bengio
Aaron Courville
We introduce a new class of models called multiresolution recurrent neural networks, which explicitly model natural language generation at m… (see more)ultiple levels of abstraction. The models extend the sequence-to-sequence framework to generate two parallel stochastic processes: a sequence of high-level coarse tokens, and a sequence of natural language words (e.g. sentences). The coarse sequences follow a latent stochastic process with a factorial representation, which helps the models generalize to new examples. The coarse sequences can also incorporate task-specific knowledge, when available. In our experiments, the coarse sequences are extracted using automatic procedures, which are designed to capture compositional structure and semantics. These procedures enable training the multiresolution recurrent neural networks by maximizing the exact joint log-likelihood over both sequences. We apply the models to dialogue response generation in the technical support domain and compare them with several competing models. The multiresolution recurrent neural networks outperform competing models by a substantial margin, achieving state-of-the-art results according to both a human evaluation study and automatic evaluation metrics. Furthermore, experiments show the proposed models generate more fluent, relevant and goal-oriented responses.
2017-02-11
Proceedings of the AAAI Conference on Artificial Intelligence (published)
doi.org
arxiv.org
Real-Time Indoor Localization in Smart Homes Using Semi-Supervised Learning
Negar Ghourchian
Michel Allegue‐martínez
Doina Precup
Long-term automated monitoring of residential or small in- dustrial properties is an important task within the broader scope of human activi… (see more)ty recognition. We present a device- free wifi-based localization system for smart indoor spaces, developed in a collaboration between McGill University and Aerˆıal Technologies. The system relies on existing wifi net- work signals and semi-supervised learning, in order to au- tomatically detect entrance into a residential unit, and track the location of a moving subject within the sensing area. The implemented real-time monitoring platform works by detect- ing changes in the characteristics of the wifi signals collected via existing off-the-shelf wifi-enabled devices in the environ- ment. This platform has been deployed in several apartments in the Montreal area, and the results obtained show the poten- tial of this technology to turn any regular home with an ex- isting wifi network into a smart home equipped with intruder alarm and room-level location detector. The machine learn- ing component has been devised so as to minimize the need for user annotation and overcome temporal instabilities in the input signals. We use a semi-supervised learning framework which works in two phases. First, we build a base learner for mapping wifi signals to different physical locations in the en- vironment from a small amount of labeled data; during its lifetime, the learner automatically re-trains when the uncer- tainty level rises significantly, without the need for further supervision. This paper describes the technical and practical issues arising in the design and implementation of such a sys- tem for real residential units, and illustrates its performance during on-going deployment.
2017-02-10
AAAI Conference on Artificial Intelligence (published)
doi.org
Training End-to-End Dialogue Systems with the Ubuntu Dialogue Corpus
Ryan Lowe
Nissan Pow
Iulian Vlad Serban
Laurent Charlin
Chia-Wei Liu
Joelle Pineau
In this paper, we construct and train end-to-end neural network-based dialogue systems usingan updated version of the recent Ubuntu Dialogue… (see more) Corpus, a dataset containing almost 1 million multi-turn dialogues, with a total of over 7 million utterances and 100 million words. This dataset is interesting because of its size, long context lengths, and technical nature; thus, it can be used to train large models directly from data with minimal feature engineering, which can be both time consuming and expensive. We provide baselines  in two different environments: one where models are trained to maximize the log-likelihood of a generated utterance  conditioned on the context of the conversation, and one where models are trained to select the correct next response from a list of candidate responses. These are both evaluated on a recall task that we call Next Utterance Classification (NUC), as well as other generation-specific metrics. Finally, we provide a qualitative error analysis to help determine the most promising directions for future research on the Ubuntu  Dialogue Corpus, and for end-to-end dialogue systems in general.
2017-01-19
Dialogue & Discourse (published)
doi.org
An Actor-Critic Algorithm for Sequence Prediction
Dzmitry Bahdanau
Philemon Brakel
Kelvin Xu
Anirudh Goyal
Ryan Lowe
Joelle Pineau
Aaron Courville
Yoshua Bengio
We present an approach to training neural networks to generate sequences using actor-critic methods from reinforcement learning (RL). Curren… (see more)t log-likelihood training methods are limited by the discrepancy between their training and testing modes, as models must generate tokens conditioned on their previous guesses rather than the ground-truth tokens. We address this problem by introducing a \textit{critic} network that is trained to predict the value of an output token, given the policy of an \textit{actor} network. This results in a training procedure that is much closer to the test phase, and allows us to directly optimize for a task-specific score such as BLEU. Crucially, since we leverage these techniques in the supervised learning setting rather than the traditional RL setting, we condition the critic network on the ground-truth output. We show that our method leads to improved performance on both a synthetic task, and for German-English machine translation. Our analysis paves the way for such methods to be applied in natural language generation tasks, such as machine translation, caption generation, and dialogue modelling.
2016-12-31
ICLR.cc/2017/conference (poster)
doi.org
openreview.net
Adversarially Learned Inference
Vincent Dumoulin
Ishmael Belghazi
Ben Poole
Alex Lamb
Martin Arjovsky
Olivier Mastropietro
Aaron Courville
We introduce the adversarially learned inference (ALI) model, which jointly learns a generation network and an inference network using an ad… (see more)versarial process. The generation network maps samples from stochastic latent variables to the data space while the inference network maps training examples in data space to the space of latent variables. An adversarial game is cast between these two networks and a discriminative network is trained to distinguish between joint latent/data-space samples from the generative network and joint samples from the inference network. We illustrate the ability of the model to learn mutually coherent inference and generation networks through the inspections of model samples and reconstructions and confirm the usefulness of the learned representations by obtaining a performance competitive with state-of-the-art on the semi-supervised SVHN and CIFAR10 tasks.
2016-12-31
ICLR.cc/2017/conference (poster)
openreview.net
openreview.net
A Benchmark for Endoluminal Scene Segmentation of Colonoscopy Images
David Vázquez
Jorge Bernal
F. Javier Sánchez
Gloria Fernández-Esparrach
Antonio M. López
Adriana Romero
Michal Drozdzal
Aaron Courville
Colorectal cancer (CRC) is the third cause of cancer death worldwide. Currently, the standard approach to reduce CRC-related mortality is to… (see more) perform regular screening in search for polyps and colonoscopy is the screening tool of choice. The main limitations of this screening procedure are polyp miss-rate and inability to perform visual assessment of polyp malignancy. These drawbacks can be reduced by designing Decision Support Systems (DSS) aiming to help clinicians in the different stages of the procedure by providing endoluminal scene segmentation. Thus, in this paper, we introduce an extended benchmark of colonoscopy image, with the hope of establishing a new strong benchmark for colonoscopy image analysis research. We provide new baselines on this dataset by training standard fully convolutional networks (FCN) for semantic segmentation and significantly outperforming, without any further post-processing, prior results in endoluminal scene segmentation.
2016-12-31
Journal of Healthcare Engineering (published)
doi.org
arxiv.org