nils-herrmann/clean_scirepeval huggingface dataset:
Augmenting Physical Models with Deep Networks for Complex Dynamics Forecasting
Authors: Yuan Yin, Vincent LE GUEN, Jérémie DONA, Emmanuel de Bezenac, Ibrahim Ayed, Nicolas THOME, patrick gallinari

Forecasting complex dynamical phenomena in settings where only partial knowledge of their dynamics is available is a prevalent problem across various scientific fields. While purely data-driven approaches are arguably insufficient in this context, standard physical modeling based approaches tend to be over-simplistic, inducing non-negligible errors. In this work, we introduce the APHYNITY framework, a principled approach for augmenting incomplete physical dynamics described by differential equations with deep data-driven models. It consists in decomposing the dynamics into two components: a physical component accounting for the dynamics for which we have some prior knowledge, and a data-driven component accounting for errors of the physical model. The learning problem is carefully formulated such that the physical model explains as much of the data as possible, while the data-driven component only describes information that cannot be captured by the physical model, no more, no less. This not only provides the existence and uniqueness for this decomposition, but also ensures interpretability and benefits generalization. Experiments made on three important use cases, each representative of a different family of phenomena, i.e. reaction-diffusion equations, wave equations and the non-linear damped pendulum, show that APHYNITY can efficiently leverage approximate physical models to accurately forecast the evolution of the system and correctly identify relevant physical parameters.
Defending Against Physically Realizable Attacks on Image Classification
Authors: Tong Wu, Liang Tong, Yevgeniy Vorobeychik

We study the problem of defending deep neural network approaches for image classification from physically realizable attacks. First, we demonstrate that the two most scalable and effective methods for learning robust models, adversarial training with PGD attacks and randomized smoothing, exhibit very limited effectiveness against three of the highest profile physical attacks. Next, we propose a new abstract adversarial model, rectangular occlusion attacks, in which an adversary places a small adversarially crafted rectangle in an image, and develop two approaches for efficiently computing the resulting adversarial examples. Finally, we demonstrate that adversarial training using our new attack yields image classification models that exhibit high robustness against the physically realizable attacks we study, offering the first effective generic defense against such attacks.
Graph-Augmented Normalizing Flows for Anomaly Detection of Multiple Time Series
Authors: Enyan Dai, Jie Chen

Anomaly detection is a widely studied task for a broad variety of data types; among them, multiple time series appear frequently in applications, including for example, power grids and traffic networks. Detecting anomalies for multiple time series, however, is a challenging subject, owing to the intricate interdependencies among the constituent series. We hypothesize that anomalies occur in low density regions of a distribution and explore the use of normalizing flows for unsupervised anomaly detection, because of their superior quality in density estimation. Moreover, we propose a novel flow model by imposing a Bayesian network among constituent series. A Bayesian network is a directed acyclic graph (DAG) that models causal relationships; it factorizes the joint probability of the series into the product of easy-to-evaluate conditional probabilities. We call such a graph-augmented normalizing flow approach GANF and propose joint estimation of the DAG with flow parameters. We conduct extensive experiments on real-world datasets and demonstrate the effectiveness of GANF for density estimation, anomaly detection, and identification of time series distribution drift.
Discovering Latent Network Topology in Contextualized Representations with Randomized Dynamic Programming
Authors: Yao Fu, Mirella Lapata

The discovery of large-scale discrete latent structures is crucial for understanding the fundamental generative processes of language. In this work, we use structured latent variables to study the representation space of contextualized embeddings and gain insight into the hidden topology of pretrained language models. However, existing methods are severely limited by issues of scalability and efficiency as working with large combinatorial spaces requires expensive memory consumption. We address this challenge by proposing a Randomized Dynamic Programming (RDP) algorithm for the approximate inference of structured models with DP-style exact computation (e.g., Forward-Backward). Our technique samples a subset of DP paths reducing memory complexity to as small as one percent. We use RDP to analyze the representation space of pretrained language models, discovering a large-scale latent network in a fully unsupervised way. The induced latent states not only serve as anchors marking the topology of the space (neighbors and connectivity), but also reveal linguistic properties related to syntax, morphology, and semantics. We also show that traversing this latent network yields unsupervised paraphrase generation.
Overcoming Catastrophic Interference using Conceptor-Aided Backpropagation
Authors: Xu He, Herbert Jaeger

Catastrophic interference has been a major roadblock in the research of continual learning. Here we propose a variant of the back-propagation algorithm, "Conceptor-Aided Backprop" (CAB), in which gradients are shielded by conceptors against degradation of previously learned tasks. Conceptors have their origin in reservoir computing, where they have been previously shown to overcome catastrophic forgetting. CAB extends these results to deep feedforward networks. On the disjoint and permuted MNIST tasks, CAB outperforms two other methods for coping with catastrophic interference that have recently been proposed.
Contrastive Divergence Learning is a Time Reversal Adversarial Game
Authors: Omer Yair, Tomer Michaeli

Contrastive divergence (CD) learning is a classical method for fitting unnormalized statistical models to data samples. Despite its wide-spread use, the convergence properties of this algorithm are still not well understood. The main source of difficulty is an unjustified approximation which has been used to derive the gradient of the loss. In this paper, we present an alternative derivation of CD that does not require any approximation and sheds new light on the objective that is actually being optimized by the algorithm. Specifically, we show that CD is an adversarial learning procedure, where a discriminator attempts to classify whether a Markov chain generated from the model has been time-reversed. Thus, although predating generative adversarial networks (GANs) by more than a decade, CD is, in fact, closely related to these techniques. Our derivation settles well with previous observations, which have concluded that CD's update steps cannot be expressed as the gradients of any fixed objective function. In addition, as a byproduct, our derivation reveals a simple correction that can be used as an alternative to Metropolis-Hastings rejection, which is required when the underlying Markov chain is inexact (e.g., when using Langevin dynamics with a large step).
A fast and accurate splitting method for optimal transport: analysis and implementation
Authors: Vien V. Mai, Jacob Lindbäck, Mikael Johansson

We develop a fast and reliable method for solving large-scale optimal transport (OT) problems at an unprecedented combination of speed and accuracy. Built on the celebrated Douglas-Rachford splitting technique, our method tackles the original OT problem directly instead of solving an approximate regularized problem, as many state-of-the-art techniques do. This allows us to provide sparse transport plans and avoid numerical issues of methods that use entropic regularization. The algorithm has the same cost per iteration as the popular Sinkhorn method, and each iteration can be executed efficiently, in parallel. The proposed method enjoys an iteration complexity $O(1/\epsilon)$ compared to the best-known $O(1/\epsilon^2)$ of the Sinkhorn method. In addition, we establish a linear convergence rate for our formulation of the OT problem. We detail an efficient GPU implementation of the proposed method that maintains a primal-dual stopping criterion at no extra cost. Substantial experiments demonstrate the effectiveness of our method, both in terms of computation times and robustness.
On Size Generalization in Graph Neural Networks
Authors: Gilad Yehudai, Ethan Fetaya, Eli Meirom, Gal Chechik, Haggai Maron

Graph neural networks (GNNs) can process graphs of different sizes but their capacity to generalize across sizes is still not well understood. Size generalization is key to numerous GNN applications, from solving combinatorial optimization problems to learning in molecular biology. In such problems, obtaining labels and training on large graphs can be prohibitively expensive, but training on smaller graphs is possible. 

This paper puts forward the size-generalization question and characterizes important aspects of that problem theoretically and empirically.
We prove that even for very simple tasks, such as counting the number of nodes or edges in a graph, GNNs do not naturally generalize to graphs of larger size. Instead, their generalization performance is closely related to the distribution of local patterns of connectivity and features and how that distribution changes from small to large graphs. Specifically, we prove that for many tasks, there are weight assignments for GNNs that can perfectly solve the task on small graphs but fail on large graphs, if there is a discrepancy between their local patterns. We further demonstrate on several tasks, that training GNNs on small graphs results in solutions which do not generalize to larger graphs. We then formalize size generalization as a domain-adaption problem and describe two learning setups where size generalization can be improved. First, as a self-supervised learning problem (SSL) over the target domain of large graphs. Second as a semi-supervised learning problem when few samples are available in the target domain. We demonstrate the efficacy of these solutions on a diverse set of benchmark graph datasets.
Graph Neural Network Guided Local Search for the Traveling Salesperson Problem
Authors: Benjamin Hudson, Qingbiao Li, Matthew Malencia, Amanda Prorok

Solutions to the Traveling Salesperson Problem (TSP) have practical applications to processes in transportation, logistics, and automation, yet must be computed with minimal delay to satisfy the real-time nature of the underlying tasks. However, solving large TSP instances quickly without sacrificing solution quality remains challenging for current approximate algorithms. To close this gap, we present a hybrid data-driven approach for solving the TSP based on Graph Neural Networks (GNNs) and Guided Local Search (GLS). Our model predicts the regret of including each edge of the problem graph in the solution; GLS uses these predictions in conjunction with the original problem graph to find solutions. Our experiments demonstrate that this approach converges to optimal solutions at a faster rate than three recent learning based approaches for the TSP. Notably, we reduce the mean optimality gap on the 100-node problem set from 1.534% to 0.705%, a 2x improvement. When generalizing from 20-node instances to the 100-node problem set, we reduce the optimality gap from 18.845% to 2.622%, a 7x improvement.
TAPEX: Table Pre-training via Learning a Neural SQL Executor
Authors: Qian Liu, Bei Chen, Jiaqi Guo, Morteza Ziyadi, Zeqi Lin, Weizhu Chen, Jian-Guang Lou

Recent progress in language model pre-training has achieved a great success via leveraging large-scale unstructured textual data. However, it is still a challenge to apply pre-training on structured tabular data due to the absence of large-scale high-quality tabular data. In this paper, we propose TAPEX to show that table pre-training can be achieved by learning a neural SQL executor over a synthetic corpus, which is obtained by automatically synthesizing executable SQL queries and their execution outputs. TAPEX addresses the data scarcity challenge via guiding the language model to mimic a SQL executor on the diverse, large-scale and high-quality synthetic corpus. We evaluate TAPEX on four benchmark datasets. Experimental results demonstrate that TAPEX outperforms previous table pre-training approaches by a large margin and achieves new state-of-the-art results on all of them. This includes the improvements on the weakly-supervised WikiSQL denotation accuracy to 89.5% (+2.3%), the WikiTableQuestions denotation accuracy to 57.5% (+4.8%), the SQA denotation accuracy to 74.5% (+3.5%), and the TabFact accuracy to 84.2% (+3.2%). To our knowledge, this is the first work to exploit table pre-training via synthetic executable programs and to achieve new state-of-the-art results on various downstream tasks. Our code can be found at https://github.com/microsoft/Table-Pretraining.
Improve Training Stability of Semi-supervised Generative Adversarial Networks with Collaborative Training
Authors: Dalei Wu, Xiaohua Liu

Improved generative adversarial network (Improved GAN) is a successful method of using generative adversarial models to solve the problem of semi-supervised learning. However, it suffers from the problem of unstable training. In this paper, we found that the instability is mostly due to the vanishing gradients on the generator. To remedy this issue, we propose a new method to use collaborative training to improve the stability of semi-supervised GAN with the combination of Wasserstein GAN. The experiments have shown that our proposed method is more stable than the original Improved GAN and achieves comparable classification accuracy on different data sets.
Domain-Robust Visual Imitation Learning with Mutual Information Constraints
Authors: Edoardo Cetin, Oya Celiktutan

Human beings are able to understand objectives and learn by simply observing others perform a task. Imitation learning methods aim to replicate such capabilities, however, they generally depend on access to a full set of optimal states and actions taken with the agent's actuators and from the agent's point of view. In this paper, we introduce a new algorithm - called Disentangling Generative Adversarial Imitation Learning (DisentanGAIL) - with the purpose of bypassing such constraints. Our algorithm enables autonomous agents to learn directly from high dimensional observations of an expert performing a task, by making use of adversarial learning with a latent representation inside the discriminator network. Such latent representation is regularized through mutual information constraints to incentivize learning only features that encode information about the completion levels of the task being demonstrated. This allows to obtain a shared feature space to successfully perform imitation while disregarding the differences between the expert's and the agent's domains. Empirically, our algorithm is able to efficiently imitate in a diverse range of control problems including balancing, manipulation and locomotive tasks, while being robust to various domain differences in terms of both environment appearance and agent embodiment.
Efficient Split-Mix Federated Learning for On-Demand and In-Situ Customization
Authors: Junyuan Hong, Haotao Wang, Zhangyang Wang, Jiayu Zhou

Federated learning (FL) provides a distributed learning framework for multiple participants to collaborate learning without sharing raw data. In many practical FL scenarios, participants have heterogeneous resources due to disparities in hardware and inference dynamics that require quickly loading models of different sizes and levels of robustness. The heterogeneity and dynamics together impose significant challenges to existing FL approaches and thus greatly limit FL's applicability. In this paper, we propose a novel Split-Mix FL strategy for heterogeneous participants that, once training is done, provides in-situ customization of model sizes and robustness. Specifically, we achieve customization by learning a set of base sub-networks of different sizes and robustness levels, which are later aggregated on-demand according to inference requirements. This split-mix strategy achieves customization with high efficiency in communication, storage, and inference. Extensive experiments demonstrate that our method provides better in-situ customization than the existing heterogeneous-architecture FL methods. Codes and pre-trained models are available: https://github.com/illidanlab/SplitMix.
Implicit ReasoNet: Modeling Large-Scale Structured Relationships with Shared Memory
Authors: Yelong Shen*, Po-Sen Huang*, Ming-Wei Chang, Jianfeng Gao

Recent studies on knowledge base completion, the task of recovering missing relationships based on recorded relations, demonstrate the importance of learning embeddings from multi-step relations. However, due to the size of knowledge bases, learning multi-step relations directly on top of observed instances could be costly. In this paper, we propose Implicit ReasoNets (IRNs), which is designed to perform large-scale inference implicitly through a search controller and shared memory. Unlike previous work, IRNs use training data to learn to perform multi-step inference through the shared memory, which is also jointly updated during training. While the inference procedure is not operating on top of observed instances for IRNs, our proposed model outperforms all previous approaches on the popular FB15k benchmark by more than 5.7%.
Tensorial Mixture Models
Authors: Or Sharir, Ronen Tamari, Nadav Cohen, Amnon Shashua

We introduce a generative model, we call Tensorial Mixture Models (TMMs) based on mixtures of basic
component distributions over local structures (e.g. patches in an image) where the dependencies between
the local-structures are represented by a "priors tensor" holding the prior probabilities of assigning a
component distribution to each local-structure.

In their general form, TMMs are intractable as the priors tensor is typically of exponential size. However,
when the priors tensor is decomposed it gives rise to an arithmetic circuit which in turn transforms the
TMM into a Convolutional Arithmetic Circuit (ConvAC). A ConvAC corresponds to a shallow (single hidden layer)
network when the priors tensor is decomposed by a CP (sum of rank-1) approach and corresponds to a
deep network when the decomposition follows the Hierarchical Tucker (HT) model.

The ConvAC representation of a TMM possesses several attractive properties. First, the inference is tractable
and is implemented by a forward pass through a deep network. Second, the architectural design of the model
follows the deep networks community design, i.e.,  the structure of TMMs is determined by just two easily
understood factors: size of pooling windows and number of channels. Finally, we demonstrate the effectiveness
of our model when tackling the problem of classification with missing data, leveraging TMMs unique ability of
tractable marginalization which leads to optimal classifiers regardless of the missingness distribution.
Make SVM great again with Siamese kernel for  few-shot learning
Authors: Bence Tilk

While deep neural networks have shown outstanding results in a wide range of applications,
learning from a very limited number of examples is still a challenging
task. Despite the difficulties of the few-shot learning, metric-learning techniques
showed the potential of the neural networks for this task. While these methods
perform well, they don’t provide satisfactory results. In this work, the idea of
metric-learning is extended with Support Vector Machines (SVM) working mechanism,
which is well known for generalization capabilities on a small dataset.
Furthermore, this paper presents an end-to-end learning framework for training
adaptive kernel SVMs, which eliminates the problem of choosing a correct kernel
and good features for SVMs. Next, the one-shot learning problem is redefined
for audio signals. Then the model was tested on vision task (using Omniglot
dataset) and speech task (using TIMIT dataset) as well. Actually, the algorithm
using Omniglot dataset improved accuracy from 98.1% to 98.5% on the one-shot
classification task and from 98.9% to 99.3% on the few-shot classification task.
Thompson Sampling for (Combinatorial) Pure Exploration
Authors: Siwei Wang, Jun Zhu

Pure exploration plays an important role in online learning. Existing work mainly focuses on the UCB approach that uses confidence bounds of all the arms to decide which one is optimal. However, the UCB approach faces some challenges when looking for the best arm set under some specific combinatorial structures. It uses the sum of upper confidence bounds within arm set $S$ to judge whether $S$ is optimal. This sum can be much larger than the exact upper confidence bound of $S$, since the empirical means of different arms in $S$ are independent. Because of this, the UCB approach requires much higher complexity than necessary. To deal with this challenge, we explore the idea of Thompson Sampling (TS) that uses independent random samples instead of the upper confidence bounds to make decisions, and design the first TS-based algorithm framework TS-Verify for (combinatorial) pure exploration. In TS-Verify, the sum of independent random samples within arm set $S$ will not exceed the exact upper confidence bound of $S$ with high probability. Hence it solves the above challange, and behaves better than existing UCB-based algorithms under the general combinatorial pure exploration setting. As for pure exploration of classic multi-armed bandit, we show that TS-Verify achieves an asymptotically optimal complexity upper bound.
Near-Black-Box Adversarial Attacks on Graph Neural Networks as An Influence Maximization Problem
Authors: Jiaqi Ma, Junwei Deng, Qiaozhu Mei

Graph neural networks (GNNs) have attracted increasing interests. With broad deployments of GNNs in real-world applications, there is an urgent need for understanding the robustness of GNNs under adversarial attacks, especially in realistic setups. In this work, we study the problem of attacking GNNs in a restricted near-black-box setup, by perturbing the features of a small set of nodes,  with no access to model parameters and model predictions. Our formal analysis draws a connection between this type of attacks and an influence maximization problem on the graph. This connection not only enhances our understanding on the problem of adversarial attack on GNNs, but also allows us to propose a group of effective near-black-box attack strategies. Our experiments verify that the proposed strategies significantly degrade the performance of three popular GNN models and outperform baseline adversarial attack strategies.
CoLES: Contrastive learning for event sequences with self-supervision
Authors: Dmitrii Babaev, Nikita Ovsov, Ivan A Kireev, Gleb Gusev, Maria Ivanova, Alexander Tuzhilin

We address the problem of self-supervised learning on discrete event sequences generated by real-world users. Self-supervised learning incorporates complex information from the raw data in low-dimensional fixed-length vector representations that could be easily applied in various downstream machine learning tasks. In this paper, we propose a new method CoLES, which adopts contrastive learning, previously used for audio and computer vision domains, to the discrete event sequences domain in a self-supervised setting. Unlike most previous studies, we theoretically justify under mild conditions that the augmentation method underlying CoLES provides representative samples of discrete event sequences. We evaluated CoLES on several public datasets and showed that CoLES representations consistently outperform other methods on different downstream tasks.