Author Archives: Thijs van Ommen

Talk by ChangYong Oh

You are all cordially invited to the AMLab seminar on Tuesday February 13 at 16:00 in C3.163, where ChangYong Oh will give a talk titled “BOCK: Bayesian Optimization with Cylindrical Kernels”. Afterwards there are the usual drinks and snacks!

Abstract: A major challenge in Bayesian Optimization is the boundary issue (Swersky, 2017) where an algorithm spends too many evaluations near the boundary of its search space. In this paper we propose BOCK, Bayesian Optimization with Cylindrical Kernels, whose basic idea is to transform the ball geometry of the search space using a cylindrical transformation. Because of the transformed geometry, the Gaussian Process-based surrogate model spends less budget searching near the boundary, while concentrating its efforts relatively more near the center of the search region, where we expect the solution to be located. We evaluate BOCK extensively, showing that it is not only more accurate and efficient, but it also scales successfully to problems with a dimensionality as high as 500. We show that the better accuracy and scalability of BOCK even allows optimizing modestly sized neural network layers, as well as neural network hyperparameters.

Talk by Jorn Peters

You are all cordially invited to the AMLab seminar on Tuesday January 30 at 16:00 in C3.163, where Jorn Peters will give a talk titled “Binary Neural Networks: an overview”. Afterwards there are the usual drinks and snacks!

Abstract: One limiting factor for deploying neural networks in real-world applications (e.g., self-driving cars or smart home appliances) is the requirement for memory, computation and power. As a consequence, it is often infeasible to employ many of today’s deep learning innovations in situations where resources are scarce. One way to combat these resource requirements of neural networks is to reduce the floating point bit-precision for the parameters and/or activations in the neural network, which effectively increases FLOPS and reduces memory requirements. Taking this to the extreme, one obtains binary neural networks, i.e., neural networks in which the parameters and/or activations are constrained to only two possible values (e.g., -1 or 1). In recent years, several methods for training binary neural networks using gradient descent have been developed. In this talk I will give an overview of (a selection) of these methods.

Talk by Veronika Cheplygina

You are all cordially invited to this week’s AMLab seminar, on Friday January 26 at 15:30 in C3.165 (so the day, time and location of the idea club). There Veronika Cheplygina (Eindhoven) will give a talk titled “Challenges of multiple instance learning in medical image analysis”. Afterwards there are the usual drinks and snacks!

Abstract: Data is often only weakly annotated: for example, for a medical image, we might know the patient’s diagnosis, but not where the abnormalities are located. Multiple instance learning (MIL), is aimed at learning classifiers from such data. In this talk, I will share a number of lessons I have learnt about MIL so far: (1) researchers do not agree on what MIL is, (2) there is no “one size fits all” approach (3) we need more thorough evaluation methods. I will give examples from several applications, including computer-aided diagnosis in chest CT images. I will also briefly discuss my work on crowdsourcing medical image annotations, and why MIL might be useful in this case.

Veronika Cheplygina is an assistant professor at the Medical Image Analysis group, Eindhoven University of Technology since February 2017. She received her Ph.D. from the Delft University of Technology for her thesis “Dissimilarity-Based Multiple Instance Learning” in 2015. As part of her PhD, she was a visiting researcher at the Max Planck Institute for Intelligent Systems in Tuebingen, Germany. From 2015 to 2016 she was a postdoc at the Biomedical Imaging Group Rotterdam, Erasmus MC. Her research interests are centered around learning scenarios where few labels are available, such as multiple instance learning, transfer learning, and crowdsourcing. Next to research, Veronika blogs about academic life at http://www.veronikach.com

Talk by Jakub Tomczak

You are all cordially invited to the first AMLab seminar of 2018 on Tuesday January 16 at 16:00 in C3.163, where Jakub Tomczak will give a talk titled “Deep Multiple Instance Learning with the Attention-based Pooling Operator”. Afterwards there are the usual drinks and snacks!

Abstract:
The computer-aided analysis of medical scans is a longstanding goal in the medical imaging field. Currently, deep learning has became a dominant methodology for supporting pathologists and radiologist. Deep learning algorithms have been successfully applied to digital pathology and radiology, nevertheless, there are still practical issues that prevent these tools to be widely used in practice. The main obstacles are low number of available cases and large size of images (a.k.a. the small n, large p problem in machine learning), and a very limited access to annotation at a pixel level that can lead to severe overfitting and large computational requirements. We propose to handle these issues by introducing a framework that processes a medical image as a collection of small patches using a single, shared neural network. The final diagnosis is provided by combining scores of individual patches using a permutation-invariant operator (combination). In machine learning community such approach is called the multi-instance learning (MIL).

During this presentation we will outline the definition of the MIL and propose a learnable permutation-invariant operator using the attention mechanism. We will provide our preliminary results on a toy problem and real-life histopathology data.

Authors:
Maximilian Ilse, Jakub Tomczak, Max Welling

Talk by Giorgio Patrini

You are all cordially invited to the AMLab seminar on Tuesday December 12 at 16:00 in C3.163, where Giorgio Patrini will give a talk titled “Federated learning on vertically partitioned data via entity resolution and homomorphic encryption”. Afterwards there are the usual drinks and snacks!

Abstract:
Consider two data providers, each maintaining private records of different feature sets about common entities. They aim to learn a linear model jointly in a federated setting, namely, data is local and a shared model is trained from locally computed updates. In contrast with most work on distributed learning, in this scenario (i) data is split vertically, i.e. by features, (ii) only one data provider knows the target variable and (iii) entities are not linked across the data providers. Hence, to the challenge of private learning, we add the potentially negative consequences of mistakes in entity resolution.

Our contribution is twofold. First, we describe a three-party end-to-end solution in two phases — privacy-preserving entity resolution and federated logistic regression over messages encrypted with an additively homomorphic scheme — , secure against a honest-but-curious adversary. The system allows learning without either exposing data in the clear or sharing which entities the data providers have in common. Our implementation is as accurate as a naive non-private solution that brings all data in one place, and scales to problems with millions of entities with hundreds of features. Second, we provide a formal analysis of the impact of entity resolution on learning.

Talk by Thomas Kipf

You are all cordially invited to the AMLab seminar on Tuesday November 14 at 16:00 in C3.163, where Thomas Kipf will give a talk titled “End-to-end learning on graphs with graph convolutional networks”. Afterwards there are the usual drinks and snacks!

Abstract: Neural networks on graphs have gained renewed interest in the machine learning community. Recent results have shown that end-to-end trainable neural network models that operate directly on graphs can challenge well-established classical approaches, such as kernel-based methods or methods that rely on graph embeddings (e.g. DeepWalk). In this talk, I will motivate such an approach from an analogy to traditional convolutional neural networks and introduce our recent variant of graph convolutional networks (GCNs) that achieves promising results on a number of semi-supervised node classification tasks. If time permits, I will further introduce two extensions of this basic framework, namely: graph auto-encoders and relational GCNs. While graph auto-encoders provide a novel way of approaching problems like link prediction or recommendation, relational GCNs allow for efficient modeling of directed relational graphs, such as knowledge bases.

Talk by Matthias Reisser

You are all cordially invited to the AMLab seminar on Tuesday November 7 at 16:00 in C3.163, where Matthias Reisser will give a talk titled “Failure Modes of distributed Variational Inference”. Afterwards there are the usual drinks and snacks!

Abstract: In this talk I want to give a summary over thoughts and experiments we performed over the last couple of weeks in trying to develop a distributed Variational Inference algorithm. Although, theoretically, we can see advantages to the proposed model, as well as cannot immediately see theoretical reasons why it should not work, the experiments demonstrate that learning in the proposed algorithm is unstable and fails catastrophically in the tested settings. I would like to show our intuition and would be glad to discuss and collect your ideas.

Talk by Elise van der Pol

You are all cordially invited to the AMLab seminar on Tuesday October 31 at 16:00 in C3.163, where Elise van der Pol will give a talk titled “Graph-based Sequential Decision Making Under Uncertainty”. Afterwards there are the usual drinks and snacks!

Abstract: In sequential decision making under uncertainty, an agent attempts to find some function that maps from states to actions, such that a reward signal is maximized, taking both immediate and future reward into account. Under the graph-based perspective, we view the problem of optimal sequential decision making as doing inference in a graphical model.
In this talk I will present some of the research related to this perspective and connect it to recent work in Deep Learning such as Value Iteration Networks and Graph Convolutional Networks.

Talk by Sara Magliacane

You are all cordially invited to the AMLab seminar on Tuesday October 24 at 16:00 in C3.163, where Sara Magliacane will give a talk titled “Joint Causal Inference from Observational and Experimental Datasets”. Afterwards there are the usual drinks and snacks!

Abstract: Joint Causal Inference (JCI) is a recently proposed causal discovery framework that aims to discover causal relations based on multiple observational and experimental datasets, also in the presence of latent variables. Compared with current methods for causal inference, JCI allows to jointly learn both the causal structure and intervention targets by pooling data from different experimental conditions in a systematic way. This systematic pooling also improves the statistical power of the independence tests used to recover the causal relations, while the introduction of context variables can improve the identifiability of causal relations. In this talk I will introduce JCI and show two possible implementations using three recent causal discovery methods from literature, Ancestral Causal Inference [Magliacane et al. 2016], [Hyttinen et al. 2014] and Greedy Fast Causal Inference [Ogarrio et al. 2016]. Moreover, I will show the benefits of JCI in an evaluation on synthetic data and in an application to the flow cytometry dataset from [Sachs et al. 2005].

Talk by Peter O’Connor

You are all cordially invited to the AMLab seminar on Tuesday October 10 at 16:00 in C3.163, where Peter O’Connor will give a talk titled “Towards Event-Based online Learning”. Afterwards there are the usual drinks and snacks!

Abstract: The world that our brains experience is quite different from the world that most of our ML models experience. Most models in machine learning are now trained by randomly sampling data from some training set, updating the model, then repeating. When temporal data is considered, it is usually split into short sequences, where each sequence is considered to be a sample from some underlying distribution of sequences, which we wish to learn. Humans on the other hand, learn online – we receive a single, never-ending sequence of inputs. Moreover, these inputs come in asynchronously, and rather than representing the state of the world at a given time, represent that some aspect of the state of the world has changed.

In this talk, I’ll discuss some work we are doing close this gap, and allow us to apply the methods used in deep learning to the more natural online-learning setting.