Deep Learning
Analyzing Cyber-Physical Systems from the Perspective of Artificial Intelligence
Veith, Eric M. S. P., Fischer, Lars, Tröschel, Martin, Nieße, Astrid
The notion of cyber-physical systems (CPS) describes the co mbination of Information and Communication Technology (ICT) and software (the "cyber" part) with physical compone nts. A CPS can emerge from embedded systems by internetworking them. The first big research program focusi ng on CPS has been started by the US National Science Foundation in 2006, where the term CPS is defined in as such tha t it "refers to the tight conjoining of and coordination between computational and physical resources," stating "[ w]e envision that the cyber-physical systems of tomorrow will far exceed those of today in terms of adaptability, auto nomy, efficiency, functionality, reliability, safety, and usability" [1]. While the notion of CPS by the U.S. National Science Foundati on, as outlined above, includes ICT, it does not explicitly name Artificial Intelligence (AI) as a necessary component to raise an embedded system to the status of a CPS. Y et, the availability of sensory data together with a co mmunications system and the ability to exert actions upon the physical world that have been planned for the whole compo und of embedded systems components readily suggests that issues of planning, the increase of reflectivity, effici ency, and lowering resource usage is achieved by increasing the "intelligence" of the overall system. As such, research ers in the domain of AI have found numerous application domains. However, the two worlds of CPS and AI usually operate on diffe rent terms: CPS require operation within well-defined boundaries, i.e., as far as possible deterministic behavio r within well-known, strictly enforced margins of error. In contrast, many AI techniques--Artificial Neural Networks (A NNs) foremost--are firmly rooted in the domain of statistics, which is probably very well seen in the ANN train ing process.
Revealing the Dark Secrets of BERT
Kovaleva, Olga, Romanov, Alexey, Rogers, Anna, Rumshisky, Anna
BERT -based architectures currently give state-of-the-art performance on many NLP tasks, but little is known about the exact mechanisms that contribute to its success. In the current work, we focus on the interpretation of self-attention, which is one of the fundamental underlying components of BERT. Using a subset of GLUE tasks and a set of handcrafted features-of-interest, we propose the methodology and carry out a qualitative and quantitative analysis of the information encoded by the individual BERT's heads. Our findings suggest that there is a limited set of attention patterns that are repeated across different heads, indicating the overall model overparametriza-tion. While different heads consistently use the same attention patterns, they have varying impact on performance across different tasks. We show that manually disabling attention in certain heads leads to a performance improvement over the regular fine-tuned BERT models. 1 Introduction Over the past year, models based on the Transformer architecture (V aswani et al., 2017) have become the de-facto standard for state-of-the-art performance on many natural language processing (NLP) tasks (Radford et al., 2018; Devlin et al., 2018). Their key feature is the self-attention mechanism that provides an alternative to conventionally used recurrent neural networks (RNN).
Semi-supervised Adversarial Active Learning on Attributed Graphs
Li, Yayong, Yin, Jie, Chen, Ling
Active learning (AL) on attributed graphs has received increasing attention with the prevalence of graph-structured data. Although AL has been widely studied for alleviating label sparsity issues with the conventional independent and identically distributed (i.i.d.) data, how to make it effective over attributed graphs remains an open research question. Existing AL algorithms on graphs attempt to reuse the classic AL query strategies designed for i.i.d. data. However, they suffer from two major limitations. First, different AL query strategies calculated in distinct scoring spaces are often naively combined to determine which nodes to be labelled. Second, the AL query engine and the learning of the classifier are treated as two separating processes, resulting in unsatisfactory performance. In this paper, we propose a SEmi-supervised Adversarial active Learning (SEAL) framework on attributed graphs, which fully leverages the representation power of deep neural networks and devises a novel AL query strategy in an adversarial way. Our framework learns two adversarial components: a graph embedding network that encodes both the unlabelled and labelled nodes into a latent space, expecting to trick the discriminator to regard all nodes as already labelled, and a semi-supervised discriminator network that distinguishes the unlabelled from the existing labelled nodes in the latent space. The divergence score, generated by the discriminator in a unified latent space, serves as the informativeness measure to actively select the most informative node to be labelled by an oracle. The two adversarial components form a closed loop to mutually and simultaneously reinforce each other towards enhancing the active learning performance. Extensive experiments on four real-world networks validate the effectiveness of the SEAL framework with superior performance improvements to state-of-the-art baselines.
Dynamic Scheduling of MPI-based Distributed Deep Learning Training Jobs
Capes, Tim, Raheja, Vishal, Kemertas, Mete, Mohomed, Iqbal
There is a general trend towards solving problems suited to d eep learning with more complex deep learning architectures trained on larger training sets. This requires longer compute times and greater data parallelizati on or model paralleliza-tion. Both data and model parallelism have been historicall y faster in parameter server architectures, but data parallelism is starting to b e faster in ring architectures due to algorithmic improvements. In this paper, we ana lyze the math behind ring architectures and make an informed adaptation of dynam ic scheduling to ring architectures. To do so, we formulate a non-convex, non-lin ear, NPhard integer programming problem and a new efficient doubling heuristic f or its solution. W e build upon Horovod: an open source ring architecture framew ork over TensorFlow. W e show that Horovod jobs have a low cost to stop and restart an d that stopping and restarting ring architecture jobs leads to faster compl etion times. These two facts make dynamic scheduling of ring architecture jobs fea sible. Lastly, we simulate a scheduler using these runs and show a more than halvin g of average job time on some workload patterns.
Testing Robustness Against Unforeseen Adversaries
Kang, Daniel, Sun, Yi, Hendrycks, Dan, Brown, Tom, Steinhardt, Jacob
Considerable work on adversarial defense has studied robustness to a fixed, known family of adversarial distortions, most frequently L_p-bounded distortions. In reality, the specific form of attack will rarely be known and adversaries are free to employ distortions outside of any fixed set. The present work advocates measuring robustness against this much broader range of unforeseen attacks---attacks whose precise form is not known when designing a defense. We propose a methodology for evaluating a defense against a diverse range of distortion types together with a summary metric UAR that measures the Unforeseen Attack Robustness against a distortion. We construct novel JPEG, Fog, Gabor, and Snow adversarial attacks to simulate unforeseen adversaries and perform a careful study of adversarial robustness against these and existing distortion types. We find that evaluation against existing L_p attacks yields highly correlated information that may not generalize to other attacks and identify a set of 4 attacks that yields more diverse information. We further find that adversarial training against either one or multiple distortions, including our novel ones, does not confer robustness to unforeseen distortions. These results underscore the need to study robustness against unforeseen distortions and provide a starting point for doing so.
QCNN: Quantile Convolutional Neural Network
A dilated causal one-dimensional convolutional neural network architecture is proposed for quantile regression. The model can forecast any arbitrary quantile, and it can be trained jointly on multiple similar time series. An application to Value at Risk forecasting shows that QCNN outperforms linear quantile regression and constant quantile estimates.
Representation Disentanglement for Multi-task Learning with application to Fetal Ultrasound
Meng, Qingjie, Pawlowski, Nick, Rueckert, Daniel, Kainz, Bernhard
One of the biggest challenges for deep learning algorithms in medical image analysis is the indiscriminate mixing of image properties, e.g. artifacts and anatomy. These entangled image properties lead to a semantically redundant feature encoding for the relevant task and thus lead to poor generalization of deep learning algorithms. In this paper we propose a novel representation disentanglement method to extract semantically meaningful and generalizable features for different tasks within a multi-task learning framework. Deep neural networks are utilized to ensure that the encoded features are maximally informative with respect to relevant tasks, while an adversarial regularization encourages these features to be disentangled and minimally informative about irrelevant tasks. We aim to use the disentangled representations to generalize the applicability of deep neural networks. We demonstrate the advantages of the proposed method on synthetic data as well as fetal ultrasound images. Our experiments illustrate that our method is capable of learning disentangled internal representations. It outperforms baseline methods in multiple tasks, especially on images with new properties, e.g. previously unseen artifacts in fetal ultrasound.
Generalization in Generative Adversarial Networks: A Novel Perspective from Privacy Protection
Wu, Bingzhe, Zhao, Shiwan, Xu, Haoyang, Chen, ChaoChao, Wang, Li, Zhang, Xiaolu, Sun, Guangyu, Zhou, Jun
In this paper, we aim to understand the generalization properties of generative adversarial networks (GANs) from a new perspective of privacy protection. Theoretically, we prove that a differentially private learning algorithm used for training the GAN does not overfit to a certain degree, i.e., the generalization gap can be bounded. Moreover, some recent works, such as the Bayesian GAN, can be re-interpreted based on our theoretical insight from privacy protection. Quantitatively, to evaluate the information leakage of well-trained GAN models, we perform various membership attacks on these models. The results show that previous Lipschitz regularization techniques are effective in not only reducing the generalization gap but also alleviating the information leakage of the training dataset.
Modeling continuous-time stochastic processes using $\mathcal{N}$-Curve mixtures
Hug, Ronny, Hübner, Wolfgang, Arens, Michael
Representations of sequential data are commonly based on the assumption that observed sequences are realizations of an unknown underlying stochastic process, where the learning problem includes determination of the model parameters. In this context the model must be able to capture the multi-modal nature of the data, without blurring between modes. This property is essential for applications like trajectory prediction or human motion modeling. Towards this end, a neural network model for continuous-time stochastic processes usable for sequence prediction is proposed. The model is based on Mixture Density Networks using B\'ezier curves with Gaussian random variables as control points (abbrev.: $\mathcal{N}$-Curves). Key advantages of the model include the ability of generating smooth multi-mode predictions in a single inference step which reduces the need for Monte Carlo simulation, as required in many multi-step prediction models, based on state-of-the-art neural networks. Essential properties of the proposed approach are illustrated by several toy examples and the task of multi-step sequence prediction. Further, the model performance is evaluated on two real world use-cases, i.e. human trajectory prediction and human motion modeling, outperforming different state-of-the-art models.
Dialog State Tracking with Reinforced Data Augmentation
Yin, Yichun, Shang, Lifeng, Jiang, Xin, Chen, Xiao, Liu, Qun
Neural dialog state trackers are generally limited due to the lack of quantity and diversity of annotated training data. In this paper, we address this difficulty by proposing a reinforcement learning (RL) based framework for data augmentation that can generate high-quality data to improve the neural state tracker. Specifically, we introduce a novel contextual bandit generator to learn fine-grained augmentation policies that can generate new effective instances by choosing suitable replacements for the specific context. Moreover, by alternately learning between the generator and the state tracker, we can keep refining the generative policies to generate more high-quality training data for neural state tracker. Experimental results on the WoZ and MultiWoZ (restaurant) datasets demonstrate that the proposed framework significantly improves the performance over the state-of-the-art models, especially with limited training data.