Three CS Students Recognized By The Computing Research Association

For this year’s Outstanding Undergraduate Researcher Award, Payal Chandak, Sophia Kolak, and Yanda Chen were among students recognized by the Computing Research Association (CRA) for their work in an area of computing research.


Payal Chandak
Finalist

Using Machine Learning to Identify Adverse Drug Effects Posing Increased Risk to Women
Payal Chandak Columbia University, Nicholas Tatonetti Columbia University

The researchers developed AwareDX – Analysing Women At Risk for Experiencing Drug toXicity – a machine learning algorithm that identifies and predicts differences in adverse drug effects between men and women by analyzing 50 years’ worth of reports in an FDA database. The algorithm automatically corrects for biases in these data that stem from an overrepresentation of male subjects in clinical research trials.

Though men and women can have different responses to medications – the sleep aid Ambien, for example, metabolizes more slowly in women, causing next-day grogginess – doctors may not know about these differences because most clinical trial data itself is biased toward men. This trickles down to impact prescribing guidelines, drug marketing, and ultimately, patients’ health. Unfortunately, pharmaceutical companies have a history of ignoring complex problems and clinical trials have singularly studied men, not even including women. As a result, there is a lot less information about how women respond to drugs compared to men. The research tries to bridge this information gap. 

 


Sophia Kolak
Finalist

It Takes a Village to Build a Robot: An Empirical Study of The ROS Ecosystem
Sophia Kolak Columbia University, Afsoon Afzal Carnegie Mellon University, Claire Le Goues Carnegie Mellon University, Michael Hilton Carnegie Mellon University, Christopher Steven Timperley Carnegie Mellon University

The Robot Operating System (ROS) is the most popular framework for robotics development. In this paper, the researchers conducted the first major empirical study of ROS, with the goal of understanding how developers collaborate across the many technical disciplines that coalesce in robotics.

Building a complete robot is a difficult task that involves bridging many technical disciplines. ROS aims to simplify development by providing reusable libraries, tools, and conventions for building a robot. Still, as building a robot requires domain expertise in software, mechanical, and electrical engineering, as well as artificial intelligence and robotics, ROS faces knowledge-based barriers to collaboration. The researchers wanted to understand how the necessity of domain-specific knowledge impacts the open-source collaboration model in ROS.

Virtually no one is an expert in every subdomain of robotics: experts who create computer vision packages likely need to rely on software designed by mechanical engineers to implement motor control. As a result, the researchers found that development in ROS is centered around a few unique subgroups each devoted to a different specialty in robotics (i.e. perception, motion). This is unlike other ecosystems, where competing implementations are the norm.

Detecting Performance Patterns with Deep Learning
Sophia Kolak Columbia University

Performance has a major impact on the overall quality of a software project. Performance bugs—bugs that substantially decrease run-time—have long been studied in software engineering, and yet they remain incredibly difficult for developers to handle. In this project, the researchers leveraged contemporary methods in machine learning to create graph embeddings of Python code that can be used to automatically predict performance.

Using un-optimized programming language concepts can lead to performance bugs and the researchers hypothesized that statistical language embeddings could help reveal these patterns. By transforming code samples into graphs that captured the control and data flow of a program, the researchers studied how various unsupervised embeddings of these graphs could be used to predict performance.  

Implementing “sort” by hand as opposed to using the built-in Python sort function is an example of a choice that typically slows down a program’s run-time. When the researchers embedded the AST and data flow of a code snippet in Euclidean space (using DeepWalk), patterns like this were captured in the embedding and allowed classifiers to learn which structures are correlated with various levels of performance.   

I was surprised by how often research changes directions,” said Sophia Kolak. In both projects, they started out with one set of questions but answered completely different ones by the end. “It showed me that, in addition to persistence, research requires open-mindedness.”

 


Yanda Chen
Honorable Mention

Cross-language Sentence Selection Via Data Augmentation and Rationale Training
Yanda Chen Columbia University, Chris Kedzie Columbia University, Suraj Nair University of Maryland, Petra Galuscakova University of Maryland, Rui Zhang Yale University, Douglas Oard University of Maryland, and Kathleen McKeown Columbia University

In this project, the researchers proposed a new approach to cross-language sentence selection, where they used models to predict sentence-level query relevance with English queries over sentences within document collections in low-resource languages such as Somali, Swahili, and Tagalog. 

The system is used as part of cross-lingual information retrieval and query-focused summarization system. For example, if a user puts in a query word “business activity” and specifies Swahili as the language of source documents, then the system will automatically retrieve the Swahili documents that are related to “business activity” and produce short summaries that are then translated from Swahili to English. 

A major challenge of the project was the lack of training data for low-resource languages. To tackle this problem, the researchers proposed to generate a relevance dataset of query-sentence pairs through data augmentation based on parallel corpora collected from the web. To mitigate the spurious correlations learned by the model, they proposed the idea of rationale training where they first trained a phrase-based statistical machine translation system and used the alignment information to provide additional supervision for the models. 

The approach achieved state-of-the-art results on both text and speech across three languages – Somali, Swahili, and Tagalog. 

 

Natural Language Processing Papers Accepted to EMNLP 2020

Six papers from the Speech & NLP group were accepted to the Empirical Methods in Natural Language Processing (EMNLP) conference. 

Generating Similes Effortlessly Like a Pro: A Style Transfer Approach for Simile Generation
Tuhin Chakrabarty Columbia University, Smaranda Muresan Columbia University, and Nanyun Peng University of Southern California and University of California, Los Angeles

Abstract:
Literary tropes, from poetry to stories, are at the crux of human imagination and communication. Figurative language, such as a simile, goes beyond plain expressions to give readers new insights and inspirations. We tackle the problem of simile generation. Generating a simile requires proper understanding for effective mapping of properties between two concepts. To this end, we first propose a method to automatically construct a parallel corpus by transforming a large number of similes collected from Reddit to their literal counterpart using structured common sense knowledge. We then fine-tune a pre-trained sequence to sequence model, BART (Lewis et al., 2019), on the literal-simile pairs to generate novel similes given a literal sentence. Experiments show that our approach generates 88% novel similes that do not share properties with the training data. Human evaluation on an independent set of literal statements shows that our model generates similes better than two literary experts 37%1 of the times, and three baseline systems including a recent metaphor generation model 71%2 of the times when compared pairwise.3 We also show how replacing literal sentences with similes from our best model in machine-generated stories improves evocativeness and leads to better acceptance by human judges.

 

Content Planning for Neural Story Generation with Aristotelian Rescoring
Seraphina Goldfarb-Tarrant University of Southern California and University of Edinburgh, Tuhin Chakrabarty Columbia University, Ralph Weischedel University of Southern California and Nanyun Peng University of Southern California and University of California, Los Angeles

Abstract:
Long-form narrative text generated from large language models manages a fluent impersonation of human writing, but only at the local sentence level, and lacks structure or global cohesion. We posit that many of the problems of story generation can be addressed via high-quality content planning, and present a system that focuses on how to learn good plot structures to guide story generation. We utilize a plot-generation language model along with an ensemble of rescoring models that each implement an aspect of good story-writing as detailed in Aristotle’s Poetics. We find that stories written with our more principled plot structure are both more relevant to a given prompt and higher quality than baselines that do not content plan, or that plan in an unprincipled way.

 

Severing the Edge Between Before and After: Neural Architectures for Temporal Ordering of Events
Miguel Ballesteros Amazon AI, Rishita Anubhai Amazon AI, Shuai Wang Amazon AI, Nima Pourdamghani Amazon AI, Yogarshi Vyas Amazon AI, Jie Ma Amazon AI, Parminder Bhatia Amazon AI, Kathleen McKeown Columbia University and Amazon AI and Yaser Al-Onaizan Amazon AI

Abstract:
In this paper, we propose a neural architecture and a set of training methods for ordering events by predicting temporal relations. Our proposed models receive a pair of events within a span of text as input and they identify temporal relations (Before, After, Equal, Vague) between them. Given that a key challenge with this task is the scarcity of annotated data, our models rely on either pre-trained representations (i.e. RoBERTa, BERT or ELMo), transfer, and multi-task learning (by leveraging complementary datasets), and self-training techniques. Experiments on the MATRES dataset of English documents establish a new state-of-the-art on this task.

 

Controllable Meaning Representation to Text Generation: Linearization and Data Augmentation Strategies
Chris Kedzie Columbia University and Kathleen McKeown Columbia University

Abstract:
We study the degree to which neural sequenceto-sequence models exhibit fine-grained controllability when performing natural language generation from a meaning representation. Using two task-oriented dialogue generation benchmarks, we systematically compare the effect of four input linearization strategies on controllability and faithfulness. Additionally, we evaluate how a phrase-based data augmentation method can improve performance. We find that properly aligning input sequences during training leads to highly controllable generation, both when training from scratch or when fine-tuning a larger pre-trained model. Data augmentation further improves control on difficult, randomly generated utterance plans.

Zero-Shot Stance Detection: A Dataset and Model using Generalized Topic Representations
Emily Allaway Columbia University and Kathleen McKeown Columbia University

Abstract:
Stance detection is an important component of understanding hidden influences in everyday life. Since there are thousands of potential topics to take a stance on, most with little to no training data, we focus on zero-shot stance detection: classifying stance from no training examples. In this paper, we present a new dataset for zero-shot stance detection that captures a wider range of topics and lexical variation than in previous datasets. Additionally, we propose a new model for stance detection that implicitly captures relationships between topics using generalized topic representations and show that this model improves performance on a number of challenging linguistic phenomena.

 

Unsupervised Cross-Lingual Part-of-Speech Tagging for Truly Low-Resource Scenarios
Ramy Eskander Columbia University, Smaranda Muresan Columbia University, and Michael Collins Columbia University

Abstract:
We describe a fully unsupervised cross-lingual transfer approach for part-of-speech (POS) tagging under a truly low resource scenario. We assume access to parallel translations between the target language and one or more source languages for which POS taggers are available. We use the Bible as parallel data in our experiments: small size, out-of-domain, and covering many diverse languages. Our approach innovates in three ways: 1) a robust approach of selecting training instances via cross-lingual annotation projection that exploits best practices of unsupervised type and token constraints, word-alignment confidence and density of projected POS, 2) a Bi-LSTM architecture that uses contextualized word embeddings, affix embeddings and hierarchical Brown clusters, and 3) an evaluation on 12 diverse languages in terms of language family and morphological typology. In spite of the use of limited and out-of-domain parallel data, our experiments demonstrate significant improvements in accuracy over previous work. In addition, we show that using multi-source information, either via projection or output combination, improves the performance for most target languages.

 

Research by CS Undergrad Published in Cell

Payal Chandak (CC ’21) developed a machine learning model, AwareDX, that helps detect adverse drug effects specific to women patients. AwareDX mitigates sex biases in a drug safety dataset maintained by the FDA.

Below, Chandak talks about how her internship under the guidance of Nicholas Tatonetti, associate professor of biomedical informatics and a member of the Data Science Institute, inspired her to develop a machine learning tool to improve healthcare for women. 


Payal Chandak

How did the project come about? 
I initiated this project during my internship at the Tatonetti Lab (T-lab) the summer after my first year. T-lab uses data science to study the side effects of drugs. I did some background research and learned that women face a two-fold greater risk of adverse events compared to men. While knowledge of sex differences in drug response is critical to drug prescription, there currently isn’t a comprehensive understanding of these differences. Dr. Tatonetti and I felt that we could use machine learning to tackle this problem and that’s how the project was born. 

How many hours did you work on the project? How long did it last? 
The project lasted about two years. We refined our machine learning (ML) model, AwareDX, over many iterations to make it less susceptible to biases in the data. I probably spent a ridiculous number of hours developing it but the journey has been well worth it. 

Were you prepared to work on it or did you learn as the project progressed? 
As a first-year student, I definitely didn’t know much when I started. Learning on the go became the norm. I understood some things by taking relevant CS classes and through reading Medium blogs and GitHub repositories –– this ability to learn independently might be one of the most valuable skills I have gained. I am very fortunate that Dr. Tatonetti guided me through this process and invested his time in developing my knowledge. 

What were the things you already knew and what were the things you had to learn while working on the project? 
While I was familiar with biology and mathematics, computer science was totally new! In fact, T-Lab launched my journey to exploring computer science. This project exposed me to the great potential of artificial intelligence (AI) for revolutionizing healthcare, which in turn inspired me to explore the discipline academically. I went back and forth between taking classes relevant to my research and applying what I learned in class to my research. As I took increasingly technical classes like ML and probabilistic modelling, I was able to advance my abilities. 

Looking back, what were the skills that you wished you had before the project? 
Having some experience with implementing real-world machine learning projects on giant datasets with millions of observations would have been very valuable. 

Was this your first project to collaborate on? How was it? 
This was my first project and I worked under the guidance of Dr. Tatonetti. I thought it was a wonderful experience – not only has it been extremely rewarding to see my work come to fruition, but the journey itself has been so valuable. And Dr. Tatonetti has been the best mentor that I could have asked for! 

Did working on this project make you change your research interests? 
I actually started off as pre-med. I was fascinated by the idea that “intelligent machines” could be used to improve medicine, and so I joined T-Lab. Over time, I’ve realized that recent advances in machine learning could redefine how doctors interact with their patients. These technologies have an incredible potential to assist with diagnosis, identify medical errors, and even recommend treatments. My perspective on how I could contribute to healthcare shifted completely, and I decided that bioinformatics has more potential to change the practice of medicine than a single doctor will ever have. This is why I’m now hoping to pursue a PhD in Biomedical Informatics. 

Do you think your skills were enhanced by working on the project? 
Both my knowledge of ML and statistics and my ability to implement my ideas have grown immensely as a result of working on this project. Also, I failed about seven times over two years. We were designing the algorithm and it was an iterative process – the initial versions of the algorithm had many flaws and we started from scratch multiple times. The entire process required a lot of patience and persistence since it took over 2 years! So, I guess it has taught me immense patience and persistence. 

Why did you decide to intern at the T-Lab? 
I was curious to learn more about the intersection of artificial intelligence and healthcare. I’m endlessly fascinated by the idea of improving the standards of healthcare by using machine learning models to assist doctors. 

Would you recommend volunteering or seeking projects out to other students? 
Absolutely. I think everyone should explore research. We have incredible labs here at Columbia with the world’s best minds leading them. Research opens the doors to work closely with them. It creates an environment for students to learn about a niche discipline and to apply the knowledge they gain in class. 

Discovering How The Brain Works Through Computation

A team led by professor Christos Papadimitriou proposes a new computational system to expand the understanding of the brain at an intermediate level, between neurons and cognitive phenomena such as language.

CS Undergrads Recognized by the Computing Research Association

For this year’s Outstanding Undergraduate Researcher Award, three computer science students received honorable mentions – Lalita Devadas, Dave Epstein, and Jessy Xinyi Han. The Computing Research Association (CRA) recognized the undergraduates for their work in an area of computing research.


Secure Montgomery Multiplication and Repeated Squares for Modular Exponentiation
Lalita Devadas Columbia University and Justin Bloom Oregon State University

The researchers worked on using some recent advances in garbling of arithmetic circuits for secure exponentiation mod N, a vital operation in many cryptosystems, including in the RSA public-key cryptosystem.

A garbled circuit is a cryptographic protocol which allows for secure two-party computation, in which two parties, Alice and Bob, each with a private input, want to compute some shared function of their inputs without either party learning the other’s input.

Their novel approach implemented the Montgomery multiplication method, which uses clever arithmetic to avoid costly division by the modulus being multiplied in. The best method they found had each wire in a circuit representing one digit of a number in base p. They developed a system of base p arithmetic which is asymptotically more efficient in the given garbled circuit architecture than any existing protocols. 

They measured performance for both approaches by counting the ciphertexts communicated for a single multiplication (a typical measure of efficiency for garbled circuit operations). They found that the base p Montgomery multiplication implementation vastly outperformed all other implementations for values of N with bit length greater than 500 (i.e., all N used for applications like RSA encryption).

“Unfortunately, our best implementations showed only incremental improvement over existing non-Montgomery-based implementations for values of N used in practice,” said Lalita Devadas. “We are still looking into further optimizations using Montgomery multiplication.”

Secure multiparty computation has many applications outside of computer science. For example, suppose five friends want to know their cumulative net worth without anyone learning anyone else’s individual net worth. This is actually a secure computation problem, since the friends want to perform some computation of their inputs while keeping said inputs private from other parties.

Oops! Predicting Unintentional Action in Video
Dave Epstein Columbia University, Boyuan Chen Columbia University, and Carl Vondrick Columbia University

The paper trains models to detect when human action is unintentional using self-supervised computer vision, an important step towards machines that can intelligently reason about the intentions behind complex human actions.

Despite enormous scientific progress over the last five to ten years, machines still struggle with tasks learned quickly and autonomously by young children, such as understanding human behavior or learning to speak a language. Epstein’s research tackles these types of problems by using self-supervised computer vision, a paradigm that predicts information naturally present in large amounts of input data such as images or videos. This stands in contrast with supervised learning, which relies on humans manually labelling data (e.g. “this is a picture of a dog”).

“I was surprised to learn that failure is an expected part of research and that it can take a long time to realize you’re failing,” said Dave Epstein. “Taking a failed idea, identifying the promising parts, and trying again leads to successful research.”

Seeding Network Influence in Biased Networks and the Benefits of Diversity
Ana-Andreea Stoica Columbia University, Jessy Xinyi Han Columbia University, and Augustin Chaintreau Columbia University

The paper explores the problem of social influence maximization and how information is diffused in a social network.

For example, it might be about what kind of news people read on social media, how many people know about job opportunities or who hears about the latest loan options from a bank. So given a social network, classical algorithms are focused on picking the best k early-adopters based on how central they are in a network, say, based on their number of connections, to maximize outreach.

However, since social inequalities are reflected in the uneven networks, classical algorithms which ignore demographics often amplify such inequalities in information access.

“We were wondering if we can do better than an algorithm that ignores demographics,” said Jessy Xinyi Han. “‘Better’ here means more people in total and more people from the disadvantaged group can receive the information.”

Through a network model with unequal communities, they developed new heuristics to take demographics into account, showing that including sensitive features in the input of most natural seed selection algorithms substantially improves diversity but also often leaves efficiency untouched or even provides a small gain.

Such analytical condition turned out to be a closed-form condition on the number of early adopters. They also validated this result on the real CS co-authorship network from DBLP.

21 papers from CS researchers accepted to NeurIPS 2019

The 33rd Conference on Neural Information Processing Systems (NeurIPS 2019) fosters the exchange of research on neural information processing systems in their biological, technological, mathematical, and theoretical aspects. 

The annual meeting is one of the premier gatherings in artificial intelligence and machine learning that featured talks, demos from industry partners as well as tutorials. Professor Vishal Misra, with colleagues from the Massachusetts Institute of Technology (MIT), held a tutorial on synthetic control.

At this year’s NeurIPS, 21 papers from the department were accepted to the conference. Computer science professors and students worked with researchers from the statistics department and the Data Science Institute.

Noise-tolerant Fair Classification
Alex Lamy Columbia University, Ziyuan Zhong Columbia University, Aditya Menon Google, Nakul Verma Columbia University

Fairness-aware learning involves designing algorithms that do not discriminate with respect to some sensitive feature (e.g., race or gender) and is usually done under the assumption that the sensitive feature available in a training sample is perfectly reliable.

This assumption may be violated in many real-world cases: for example, respondents to a survey may choose to conceal or obfuscate their group identity out of fear of potential discrimination. In the paper, the researchers show that fair classifiers can still be used given noisy sensitive features by simply changing the desired fairness-tolerance. Their procedure is empirically effective on two relevant real-world case-studies involving sensitive feature censoring.

Poisson-randomized Gamma Dynamical Systems
Aaron Schein UMass Amherst, Scott Linderman Columbia University, Mingyuan Zhou University of Texas at Austin, David Blei Columbia University, Hanna Wallach MSR NYC

This paper presents a new class of state space models for count data. It derives new properties of the Poisson-randomized gamma distribution for efficient posterior inference.

Using Embeddings to Correct for Unobserved Confounding in Networks
Victor Veitch Columbia University, Yixin Wang Columbia University, David Blei Columbia University

This paper address causal inference in the presence of unobserved confounder when proxy is available for the confounders in the form of a network connecting the units. For example, the link structure of friendships in a social network reveals information about the latent preferences of people in that network. The researchers show how modern network embedding methods can be exploited to harness the network estimation for efficient causal adjustment.

Variational Bayes Under Model Misspecification
Yixin Wang Columbia University, David Blei Columbia University

The paper characterizes the theoretical properties of a popular machine learning algorithm, variational Bayes (VB). The researchers studied the VB under model misspecification, which is the setting that is most aligned with the practice, and show that the VB posterior is asymptotically normal and centers at the value that minimizes the Kullback-Leibler (KL) divergence to the true data-generating distribution. 

As a consequence, they found that the model misspecification error dominates the variational approximation error in VB posterior predictive distributions. In other words, VB pays a negligible price in producing posterior predictive distributions. It explains the widely observed phenomenon that VB achieves comparable predictive accuracy with MCMC even though VB uses an approximating family.

Poincaré Recurrence, Cycles and Spurious Equilibria in Gradient-Descent-Ascent for Non-Convex Non-Concave Zero-Sum Games
Emmanouil-Vasileios Vlatakis-Gkaragkounis Columbia University, Lampros Flokas Columbia University, Georgios Piliouras Singapore University of Technology and Design

The paper introduces a model that captures a min-max competition over complex error landscapes and shows that even a simplified model can provably replicate some of the most commonly reported failure modes of GANs (non-convergence, deadlock in suboptimal states, etc).

Moreover, the researchers were able to understand the hidden structure in these systems — the min-max competition can lead to system behavior that is similar to that of energy preserving systems in physics (e.g. connected pendulums, many-body problems, etc). This makes it easier to understand why these systems can fail and gives new tools in the design of algorithms for training GANs. 

Near-Optimal Reinforcement Learning in Dynamic Treatment Regimes
Junzhe Zhang Columbia University, Elias Bareinboim Columbia University

Dynamic Treatment Regimes (DTRs) are particularly effective for managing chronic disorders and is arguably one of the key aspects towards more personalized decision-making. The researchers developed the first adaptive algorithm that achieves near-optimal regret in DTRs in online settings, while leveraging the abundant, yet imperfect confounded observations. Applications are given to personalized medicine and treatment recommendation in clinical decision support.

Paraphrase Generation with Latent Bag of Words
Yao Fu Columbia University, Yansong Feng Peking University, John Cunningham University of Columbia

The paper proposes a latent bag of words model for differentiable content planning and surface realization in text generation. This model generates paraphrases with clear steps, adding interpretability and controllability of existing neural text generation models. 

Adapting Neural Networks for the Estimation of Treatment Effects
Claudia Shi Columbia University, David Blei Columbia University, Victor Veitch Columbia University

This paper addresses how to design neural networks to get very accurate estimates of causal effects from observational data. The researchers propose two methods based on insights from the statistical literature on the estimation of treatment effects. 

The first is a new architecture, the Dragonnet, that exploits the sufficiency of the propensity score for estimation adjustment. The second is a regularization procedure, targeted regularization, that induces a bias towards models that have non-parametrically optimal asymptotic properties “out-of-the-box”. Studies on benchmark datasets for causal inference show these adaptations outperform existing methods.

Efficiently Avoiding Saddle Points with Zero Order Methods: No Gradients Required
Emmanouil-Vasileios Vlatakis-Gkaragkounis Columbia University, Lampros Flokas Columbia University, Georgios Piliouras Singapore University of Technology and Design

The researchers prove that properly tailored zero-order methods are as effective as their first-order counterparts. This analysis requires a combination of tools from optimization theory, probability theory and dynamical systems to show that even without perfect knowledge of the shape of the error landscape, effective optimization is possible.

Metric Learning for Adversarial Robustness
Chengzhi Mao Columbia University, Ziyuan Zhong Columbia University, Junfeng Yang Columbia University, Carl Vondrick Columbia University, Baishakhi Ray Columbia University

Deep networks are well-known to be fragile to adversarial attacks. The paper introduces a novel Triplet Loss Adversarial (TLA) regulation that is the first method that leverages metric learning to improve the robustness of deep networks. This method is inspired by the evidence that deep networks suffer from distorted feature space under adversarial attacks. The method increases the model robustness and efficiency for the detection of adversarial attacks significantly.

Efficient Symmetric Norm Regression via Linear Sketching
Zhao Song University of Washington, Ruosong Wang Carnegie Mellon University, Lin Yang Johns Hopkins University, Hongyang Zhang TTIC, Peilin Zhong Columbia University

The paper studies linear regression problems with general symmetric norm loss and gives efficient algorithms for solving such linear regression problems via sketching techniques.

Rethinking Generative Coverage: A Pointwise Guaranteed Approach
Peilin Zhong Columbia University, Yuchen Mo Columbia University, Chang Xiao Columbia University, Pengyu Chen Columbia University, Changxi Zheng Columbia University

The paper presents a novel and  formal definition of mode coverage for generative models. It also gives a boosting algorithm to achieve this mode coverage guarantee.

How Many Variables Should Be Entered in a Principal Component Regression Equation?
Ji Xu Columbia University, Daniel Hsu Columbia University

The researchers studied the least-squares linear regression over $N$ uncorrelated Gaussian features that are selected in order of decreasing variance with the number of selected features $p$ can be either smaller or greater than the sample size $n$. And give an average-case analysis of the out-of-sample prediction error as $p,n,N \to \infty$ with $p/N \to \alpha$ and $n/N \to \beta$, for some constants $\alpha \in [0,1]$ and $\beta \in (0,1)$. In this average-case setting, the prediction error exhibits a “double descent” shape as a function of $p$. This also establishes conditions under which the minimum risk is achieved in the interpolating ($p>n$) regime.

Adaptive Influence Maximization with Myopic Feedback
Binghui Peng Columbia University, Wei Chen Microsoft Research

The paper investigates the adaptive influence maximization problem and provides upper and lower bounds for the adaptivity gaps under myopic feedback model. The results confirm a long standing open conjecture by Golovin and Krause (2011).

Towards a Zero-One Law for Column Subset Selection
Zhao Song University of Washington, David Woodruff Carnegie Mellon University, Peilin Zhong Columbia University

The researchers studied low-rank matrix approximation with general loss function and showed that if the loss function has several good properties, then there is an efficient way to compute a good low-rank approximation. Otherwise, it could be hard to compute a good low-rank approximation efficiently.

Average Case Column Subset Selection for Entrywise l1-Norm Loss
Zhao Song University of Washington, David Woodruff Carnegie Mellon University, Peilin Zhong Columbia University

The researchers studied how to compute an l1-norm loss low-rank matrix approximation to a given matrix. And showed that if the given matrix can be decomposed into a low-rank matrix and a noise matrix with a mild distributional assumption, we can obtain a (1+eps) approximation to the optimal solution.

A New Distribution on the Simplex with Auto-Encoding Applications
Andrew Stirn Columbia University, Tony Jebara Spotify, David Knowles Columbia University

The researchers developed a surrogate distribution for the Dirichlet that offers explicit, tractable reparameterization, the ability to capture sparsity, and has barycentric symmetry properties (i.e. exchangeability) equivalent to the Dirichlet. Previous works have used the Kumaraswamy distribution in a stick-breaking process to create a non-exchangeable distribution on the simplex. The method was improved by restoring exchangeability and demonstrating that approximate exchangeability is efficiently achievable. Lastly, the method was showcased in a variety of VAE semi-supervised learning tasks.

Discrete Flows: Invertible Generative Models of Discrete Data
Dustin Tran Google Brain, Keyon Vafa Columbia University, Kumar Agrawal Google AI Resident, Laurent Dinh Google Brain, Ben Poole Google Brain

While normalizing flows have led to significant advances in modeling high-dimensional continuous distributions, their applicability to discrete distributions remains unknown. The researchers extend normalizing flows to discrete events, using a simple change-of-variables formula not requiring log-determinant-Jacobian computations. Empirically, they find that discrete flows obtain competitive performance with or outperform autoregressive baselines on various tasks, including addition, Potts models, and language models.

Characterization and Learning of Causal Graphs with Latent Variables from Soft Interventions
Murat Kocaoglu MIT-IBM Watson AI Lab IBM Research, Amin Jaber Purdue University, Karthikeyan Shanmugam MIT-IBM Watson AI Lab IBM Research NY, Elias Bareinboim Columbia University

This work is all about learning causal relationships – the classic aim of which is to characterize all possible sets that could produce the observed data. In the paper, the researchers provide a complete characterization of all possible causal graphs with observational and interventional data involving so-called ‘soft interventions’ on variables when the targets of soft interventions are known.

This work potentially could lead to discovery of other novel learning algorithms that are both sound and complete.

Identification of Conditional Causal Effects Under Markov Equivalence
Amin Jaber Purdue University, Jiji Zhang Lingnan University, Elias Bareinboim Columbia University

Causal identification is the problem of deciding whether a causal distribution is computable from a combination of qualitative knowledge about the underlying data-generating process, which is usually encoded in the form of a causal graph, and an observational distribution. Despite the obvious need for identifying causal effects throughout the data-driven sciences, in practice, finding the causal graph is a notoriously challenging task.

In this work, the researchers provide a relaxation of the requirement of having to specify the causal graph (based on substantive knowledge) and allow the input of the inference to be an equivalence class of causal graphs, which can be inferred from data. Specifically, they propose the first general algorithm to learn conditional causal effects entirely from data. This result is particularly useful for evaluating the impact of conditional plans and stochastic policies, which appear both in AI (in the context of reinforcement learning) and in the data-driven sciences.

Efficient Identification in Linear Structural Causal Models with Instrumental Cutsets
Daniel Kumor Purdue University, Bryant Chen Brex Inc., Elias Bareinboim Columbia University

Regression analysis is one of the most common tools used in modern data science. While there is a great understanding and powerful technology to perform regression analysis in high dimensional spaces, the output of such a method is purely associational and devoid of any causal interpretation.

The researchers studied the problem of identification of structural (causal) coefficients in linear systems (deciding whether regression coefficients are amenable to causal interpretation, etc). Building on a technique called instrumental variables, they developed a new method called Instrumental Cutset, which partitions the systems into tractable components such that identification can be decided more efficiently. The resulting algorithm was efficient and strictly more powerful than the current state-of-the-art methods.

When Does Failure Become a Good Thing?

Assistant Professor Allison Bishop takes a look at failure and how people can learn from “unsuccessful” research.

When it comes to research and getting papers into cryptography conferences, there usually has to be a “positive” result — either a new theorem must be proven, a new algorithm must be presented, or a successful attack on an existing algorithm must be obtained. If researchers try to accomplish a lofty goal and fall short, but manage to achieve a smaller goal, they typically present only the smaller goal as if it was the point on its own.

Allison Bishop

“I’ve found that not every research paper magically comes together and has a “great” result,” said Allison Bishop, who has been teaching since 2013. “Our community doesn’t really talk about the research process and I wanted to highlight research where even if it “failed” there is still something to learn from it.”

Through the years Bishop noticed the lack of a venue to talk about all kinds of research. When she and other researchers studied obfuscation it resulted in a paper “In Pursuit of Clarity In Obfuscation”. In the paper they talked about how they “failed” but managed to still learn from their mistakes. Their topic on failure was not considered a “standard” that could be published and they were not able to submit it to a conference. But Bishop, along with PhD students Luke Kowalczyk and Kevin Shi, really wanted to get their findings out and share it with other researchers.

And so, a conference dedicated to disseminating insightful failures of the cryptology research community was born. The Conference for Failed Approaches and Insightful Losses in Cryptology or CFAIL featured seven previously unpublished papers for a day of talks by computer scientists on insightful failures spanning the full range from cryptanalysis (trying to break systems) to cryptographic theory and design (constructing new systems and proving things about specific systems or about abstract systems, etc.).

“CFAIL is great for our field in that it promotes openness and accessibility for these kinds of ideas which are typically sort of intimate,” said Luke Kowalczyk, who completed his PhD in November of last year. “When approaching new problems, it’s always helpful to see the approaches of other researchers, even if they were not successful. However, it’s rare to see failed approaches explained in a public and formal setting.”

They were not alone in thinking about the lack of dialogue on research failures. At the time of the conference, a thread on Hacker News (a tech news aggregator) discussed the incentive structures of academia. Shared Kowalczyk, “I was proud to see CFAIL cited as an example of a scientific field with a formal venue to help promote this kind of openness.”

“There is a deeply ingrained human tendency to fear that being open about failure will make other people think you are dumb,” said Bishop. On the contrary, the researchers at CFAIL were some of the “most creative, bold, and deeply intelligent people.” And the atmosphere it created was energizing for the participants — the audience got pretty involved and felt comfortable asking questions, and even started thinking about some of the open research problems in real time. Continued Bishop, ”I think talking about failure is probably the best scientific communication strategy left that is severely underused.”

Bishop will continue to promote openness in scientific research with another CFAIL at Crypto 2020. This time around it will be a workshop at the conference and a call for papers will be out soon.