nils-herrmann/clean_scirepeval huggingface dataset:
An information-theoretic analysis of deep latent-variable models
Authors: Alex Alemi, Ben Poole, Ian Fischer, Josh Dillon, Rif A. Saurus, Kevin Murphy

We present an information-theoretic framework for understanding trade-offs in unsupervised learning of deep latent-variables models using variational inference. This framework emphasizes the need to consider latent-variable models along two dimensions: the ability to reconstruct inputs (distortion) and the communication cost (rate). We derive the optimal frontier of generative models in the two-dimensional rate-distortion plane, and show how the standard evidence lower bound objective is insufficient to select between points along this frontier. However, by performing targeted optimization to learn generative models with different rates, we are able to learn many models that can achieve similar generative performance but make vastly different trade-offs in terms of the usage of the latent variable. Through experiments on MNIST and Omniglot with a variety of architectures, we show how our framework sheds light on many recent proposed extensions to the variational autoencoder family.
Hierarchical Visuomotor Control of Humanoids
Authors: Josh Merel, Arun Ahuja, Vu Pham, Saran Tunyasuvunakool, Siqi Liu, Dhruva Tirumala, Nicolas Heess, Greg Wayne

We aim to build complex humanoid agents that integrate perception, motor control, and memory. In this work, we partly factor this problem into low-level motor control from proprioception and high-level coordination of the low-level skills informed by vision. We develop an architecture capable of surprisingly flexible, task-directed motor control of a relatively high-DoF humanoid body by combining pre-training of low-level motor controllers with a high-level, task-focused controller that switches among low-level sub-policies. The resulting system is able to control a physically-simulated humanoid body to solve tasks that require coupling visual perception from an unstabilized egocentric RGB camera during locomotion in the environment.
Effects of Linguistic Labels on Learned Visual Representations in Convolutional Neural Networks: Labels matter!
Authors: Seoyoung Ahn, Gregory Zelinsky, Gary Lupyan

We investigated the changes in visual representations learnt by CNNs when using different linguistic labels (e.g., trained with basic-level labels only, superordinate-level only, or both at the same time) and how they compare to human behavior when asked to select which of three images is most different. We compared CNNs with identical architecture and input, differing only in what labels were used to supervise the training. The results showed that in the absence of labels, the models learn very little categorical structure that is often assumed to be in the input. Models trained with superordinate labels (vehicle, tool, etc.) are most helpful in allowing the models to match human categorization, implying that human representations used in odd-one-out tasks are highly modulated by semantic information not obviously present in the visual input.
Cortico-cerebellar networks as decoupled neural interfaces
Authors: Joseph Pemberton, Ellen Boven, Richard Apps, Rui Ponte Costa

The brain solves the credit assignment problem remarkably well. For credit to be correctly assigned across multiple cortical areas a given area should, in principle, wait for others to finish their computation. How the brain deals with this locking problem has remained unclear. Deep learning methods suffer from similar locking constraints both on the forward and backward phase. Recently, decoupled neural interfaces (DNI) were introduced as a solution to the forward and backward locking problems.
Here we propose that a specialised brain region, the cerebellum, helps the cerebral cortex solve the locking problem closely matching the computations and architecture of DNI. In particular, we propose that classical cerebellar forward and inverse models are equivalent to solving the backward and forward locking problems, respectively. To demonstrate the potential of this framework we focus on modelling a given brain area as a recurrent neural network in which the cerebellum approximates temporal feedback signals as provided by BPTT. We tested the cortico-cerebellar-DNI (CC-DNI) model in a range of sensorimotor and cognitive tasks that have been shown to be cerebellar-dependent. First, we show that the CC-DNI unlocking mechanisms can facilitate learning in a simple target reaching task. Next, by building on the sequential MNIST task we demonstrate that these results generalise to more complex sensorimotor tasks. Our cortico-cerebellar model readily applies to a wider range of modalities, to demonstrate this we tested the model in a cognitive task, caption generation. Models without the cerebellar-DNI component exhibit deficits similar to those observed in cerebellar patients in both motor and cognitive tasks. Moreover, we used CC-DNI to generate a set of specific neuroscience predictions. Finally, we introduce a CC-DNI model with highly sparse connectivity as observed in the cerebellum, which substantially reduces the number of parameters while improving learning through decorrelation.
Overall, our work offers a novel perspective on the cerebellum as a brain-wide decoupling machine for efficient credit assignment and opens a new avenue of research between deep learning and neuroscience.
Why Does Hierarchy (Sometimes) Work So Well in Reinforcement Learning?
Authors: Ofir Nachum, Haoran Tang, Xingyu Lu, Shixiang Gu, Honglak Lee, Sergey Levine

Hierarchical reinforcement learning has demonstrated significant success at solving difficult reinforcement learning (RL) tasks. Previous works have motivated the use of hierarchy by appealing to a number of intuitive benefits, including learning over temporally extended transitions, exploring over temporally extended periods, and training and exploring in a more semantically meaningful action space, among others. However, in fully observed, Markovian settings, it is not immediately clear why hierarchical RL should provide benefits over standard "shallow" RL architectures. In this work, we isolate and evaluate the claimed benefits of hierarchical RL on a suite of tasks encompassing locomotion, navigation, and manipulation.
Surprisingly, we find that most of the observed benefits of hierarchy can be attributed to improved exploration, as opposed to easier policy learning or imposed hierarchical structures. Given this insight, we present exploration techniques inspired by hierarchy that achieve performance competitive with hierarchical RL while at the same time being much simpler to use and implement.
On the Tunability of Optimizers in Deep Learning
Authors: Prabhu Teja S*, Florian Mai*, Thijs Vogels, Martin Jaggi, Francois Fleuret

There is no consensus yet on the question whether adaptive gradient methods like Adam are easier to use than non-adaptive optimization methods like SGD. In this work, we fill in the important, yet ambiguous concept of ‘ease-of-use’ by defining an optimizer’s tunability:  How easy is it to find good hyperparameter configurations using automatic random hyperparameter search? We propose a practical and universal quantitative measure for optimizer tunability that can form the basis for a fair optimizer benchmark.  Evaluating a variety of optimizers on an extensive set of standard datasets and architectures, we find  that Adam is the most tunable for the majority of problems, especially with a low budget for hyperparameter tuning.
AUTOMATED DESIGN USING NEURAL NETWORKS AND GRADIENT DESCENT
Authors: Oliver Hennigh

We propose a novel method that makes use of deep neural networks and gradient decent to perform automated design on complex real world engineering tasks. Our approach works by training a neural network to mimic the fitness function of a design optimization task and then, using the differential nature of the neural network, perform gradient decent to maximize the fitness. We demonstrate this methods effectiveness by designing an optimized heat sink and both 2D and 3D airfoils that maximize the lift drag ratio under steady state flow conditions. We highlight that our method has two distinct benefits over other automated design approaches. First, evaluating the neural networks prediction of fitness can be orders of magnitude faster then simulating the system of interest. Second, using gradient decent allows the design space to be searched much more efficiently then other gradient free methods. These two strengths work together to overcome some of the current shortcomings of automated design.
Straight to the Gradient: Learning to Use Novel Tokens for Neural Text Generation
Authors: Xiang Lin, SIMENG HAN, Shafiq Joty

Advanced large-scale neural language models have led to significant success in many natural language generation tasks. However, the most commonly used training objective, Maximum Likelihood Estimation (MLE), has been shown to be problematic, where the trained model prefers using dull and repetitive phrases. In this work, we introduce ScaleGrad, a modification straight to the gradient of the loss function, to remedy the degeneration issues of the standard MLE objective. By directly maneuvering the gradient information, ScaleGrad makes the model learn to use novel tokens during training. Empirical results show the effectiveness of our method not only in open-ended generation, but also in directed generation. With the simplicity in architecture, our method can serve as a general training objective that is applicable to most of the neural text generation tasks.
Generalized Natural Gradient Flows in Hidden Convex-Concave Games and GANs
Authors: Andjela Mladenovic, Iosif Sakos, Gauthier Gidel, Georgios Piliouras

Game-theoretic formulations in machine learning have recently risen in prominence, whereby entire modeling paradigms are best captured as zero-sum games. Despite their popularity, however, their dynamics are still poorly understood. This lack of theory is often substantiated with painful empirical observations of volatile training dynamics and even divergence. Such results highlight the need to develop an appropriate theory with convergence guarantees that are powerful enough to inform practice. This paper studies the generalized Gradient Descent-Ascent (GDA) flow in a large class of non-convex non-concave Zero-Sum games dubbed Hidden Convex-Concave games, a class of games that includes GANs. We focus on two specific geometries: a novel geometry induced by the hidden convex-concave structure that we call the hidden mapping geometry and the Fisher information geometry. For the hidden mapping geometry, we prove global convergence under mild assumptions. In the case of Fisher information geometry, we provide a complete picture of the dynamics in an interesting special setting of team competition via invariant function analysis.
RotationOut as a Regularization Method for Neural Network
Authors: Kai Hu, Barnabas Poczos

In this paper, we propose a novel regularization method, RotationOut, for neural networks. 
Different from Dropout that handles each neuron/channel independently, RotationOut regards its input layer as an entire vector and introduces regularization by randomly rotating the vector. 
RotationOut can also be used in convolutional layers and recurrent layers with a small modification.
We further use a noise analysis method to interpret the difference between RotationOut and Dropout in co-adaptation reduction. 
Using this method, we also show how to use RotationOut/Dropout together with Batch Normalization. 
Extensive experiments in vision and language tasks are conducted to show the effectiveness of the proposed method. 
Codes will be available.
Meta-Learning an Inference Algorithm for Probabilistic Programs
Authors: Gwonsoo Che, Hongseok Yang

We present a meta-algorithm for learning a posterior-inference algorithm for restricted probabilistic programs. Our meta-algorithm takes a training set of probabilistic programs that describe models with observations, and attempts to learn an efficient method for inferring the posterior of a similar program.
A key feature of our approach is the use of what we call a white-box inference algorithm that extracts information directly from model descriptions themselves, given as programs. Concretely, our white-box inference algorithm is equipped with multiple neural networks, one for each type of atomic command, and computes an approximate posterior of a given probabilistic program by analysing individual atomic commands in the program using these networks. The parameters of these networks are then learnt from a training set by our meta-algorithm.
We empirically demonstrate that the learnt inference algorithm generalises well to programs that are new in terms of both parameters and structures, and report cases where our approach
has advantages over alternative approaches such as HMC in terms of test-time efficiency.
The overall results show the promise as well as remaining challenges of our approach.
Federated learning using mixture of experts
Authors: Edvin Listo Zec, John Martinsson, Olof Mogren, Leon René Sütfeld, Daniel Gillblad

Federated learning has received attention for its efficiency and privacy benefits,in settings where data is distributed among devices.   Although federated learning shows significant promise as a key approach when data cannot be shared or centralized, current incarnations show limited privacy properties and have short-comings  when  applied  to  common  real-world  scenarios.   One  such  scenario is heterogeneous data among devices, where data may come from different generating distributions. In this paper, we propose a federated learning framework using a mixture of experts to balance the specialist nature of a locally trained model with the generalist knowledge of a global model in a federated learning setting.  Our results show that the mixture of experts model is better suited as a personalized model for devices when data is heterogeneous, outperforming both global and lo-cal models.  Furthermore, our framework gives strict privacy guarantees, which allows clients to select parts of their data that may be excluded from the federation.   The evaluation shows that the proposed solution is robust to the setting where some users require a strict privacy setting and do not disclose their models to a central server at all, opting out from the federation partially or entirely.  The proposed framework is general enough to include any kind of machine learning models, and can even use combinations of different kinds.
AdaShift: Decorrelation and Convergence of Adaptive Learning Rate Methods
Authors: Zhiming Zhou*, Qingru Zhang*, Guansong Lu, Hongwei Wang, Weinan Zhang, Yong Yu

Adam is shown not being able to converge to the optimal solution in certain cases. Researchers recently propose several algorithms to avoid the issue of non-convergence of Adam, but their efficiency turns out to be unsatisfactory in practice. In this paper, we provide a new insight into the non-convergence issue of Adam as well as other adaptive learning rate methods. We argue that there exists an inappropriate correlation between gradient $g_t$ and the second moment term $v_t$ in Adam ($t$ is the timestep), which results in that a large gradient is likely to have small step size while a small gradient may have a large step size. We demonstrate that such unbalanced step sizes are the fundamental cause of non-convergence of Adam, and we further prove that decorrelating $v_t$ and $g_t$ will lead to unbiased step size for each gradient, thus solving the non-convergence problem of Adam. Finally, we propose AdaShift, a novel adaptive learning rate method that decorrelates $v_t$ and $g_t$ by temporal shifting, i.e., using temporally shifted gradient $g_{t-n}$ to calculate $v_t$. The experiment results demonstrate that AdaShift is able to address the non-convergence issue of Adam, while still maintaining a competitive performance with Adam in terms of both training speed and generalization.
Generative Adversarial Networks For Data Scarcity Industrial Positron Images With Attention
Authors: Mingwei Zhu, Min Zhao, Min Yao, Ruipeng Guo

In the industrial field, the positron annihilation is not affected by complex environment, and the gamma-ray photon penetration is strong, so the nondestructive detection of industrial parts can be realized. Due to the poor image quality caused by gamma-ray photon scattering, attenuation and short sampling time in positron process, we propose the idea of combining deep learning to generate positron images with good quality and clear details by adversarial nets. The structure of the paper is as follows: firstly, we encode to get the hidden vectors of medical CT images based on transfer Learning, and use PCA to extract positron image features. Secondly, we construct a positron image memory based on attention mechanism as a whole input to the adversarial nets which uses medical hidden variables as a query. Finally, we train the whole model jointly and update the input parameters until convergence. Experiments have proved the possibility of generating rare positron images for industrial non-destructive testing using countermeasure networks, and good imaging results have been achieved.
Safe Linear-Quadratic Dual Control with Almost Sure Performance Guarantee
Authors: Yiwen Lu, Yilin Mo

This paper considers the linear-quadratic dual control problem where the system parameters need to be identified and the control objective needs to be optimized in the meantime. Contrary to existing works on data-driven linear-quadratic regulation, which typically provide error or regret bounds within a certain probability, we propose an online algorithm that guarantees the asymptotic optimality of the controller in the almost sure sense. Our dual control strategy consists of two parts: a switched controller with time-decaying exploration noise and Markov parameter inference based on the cross-correlation between the exploration noise and system output. Central to the almost sure performance guarantee is a safe switched control strategy that falls back to a known conservative but stable controller when the actual state deviates significantly from the target state. We prove that this switching strategy rules out any potential destabilizing controllers from being applied, while the performance gap between our switching strategy and the optimal linear state feedback is exponentially small. Under our dual control scheme, the parameter inference error scales as $O(T^{-1/4+\epsilon})$, while the suboptimality gap of control performance scales as $O(T^{-1/2+\epsilon})$, where $T$ is the number of time steps, and $\epsilon$ is an arbitrarily small positive number. Simulation results on an industrial process example are provided to illustrate the effectiveness of our proposed strategy.
Communication in Multi-Agent Reinforcement Learning: Intention Sharing
Authors: Woojun Kim, Jongeui Park, Youngchul Sung

Communication is one of the core components for learning coordinated behavior in multi-agent systems.
In this paper, we propose a new communication scheme named  Intention Sharing (IS) for multi-agent reinforcement learning in order to enhance the coordination among agents. In the proposed IS scheme, each agent generates an imagined trajectory by modeling the environment dynamics and other agents' actions. The imagined trajectory is the simulated future trajectory of each agent based on the learned model of the environment dynamics and other agents and represents each agent's future action plan. Each agent compresses this imagined trajectory capturing its future action plan to generate its intention message for communication by applying an attention mechanism to learn the relative importance of the components in the imagined trajectory based on the received message from other agents. Numeral results show that the proposed IS scheme outperforms other communication schemes in multi-agent reinforcement learning.
Learning Factorized Multimodal Representations
Authors: Yao-Hung Hubert Tsai, Paul Pu Liang, Amir Zadeh, Louis-Philippe Morency, Ruslan Salakhutdinov

Learning multimodal representations is a fundamentally complex research problem due to the presence of multiple heterogeneous sources of information. Although the presence of multiple modalities provides additional valuable information, there are two key challenges to address when learning from multimodal data: 1) models must learn the complex intra-modal and cross-modal interactions for prediction and 2) models must be robust to unexpected missing or noisy modalities during testing. In this paper, we propose to optimize for a joint generative-discriminative objective across multimodal data and labels. We introduce a model that factorizes representations into two sets of independent factors: multimodal discriminative and modality-specific generative factors. Multimodal discriminative factors are shared across all modalities and contain joint multimodal features required for discriminative tasks such as sentiment prediction. Modality-specific generative factors are unique for each modality and contain the information required for generating data. Experimental results show that our model is able to learn meaningful multimodal representations that achieve state-of-the-art or competitive performance on six multimodal datasets. Our model demonstrates flexible generative capabilities by conditioning on independent factors and can reconstruct missing modalities without significantly impacting performance. Lastly, we interpret our factorized representations to understand the interactions that influence multimodal learning.
Bayesian neural network parameters provide insights into the earthquake rupture physics.
Authors: Sabber Ahamed

I present a simple but informative approach to gain insight into the Bayesian neural network (BNN) trained parameters. I used 2000 dynamic rupture simulations to train a BNN model to predict if an earthquake can break through a simple 2D fault. In each simulation, fault geometry, stress conditions, and friction parameters vary. The trained BNN parameters show that the network learns the physics of earthquake rupture. Neurons with high positive weights contribute to the earthquake rupture and vice versa.  The results show that the stress condition of the fault plays a critical role in determining its strength. The stress is also the top source of uncertainty, followed by the dynamic friction coefficient. When stress and friction drop of a fault have higher value and are combined with higher weighted neurons, the prediction score increases, thus fault likely to be ruptured. Fault's width and height have the least amount of uncertainty, which may not be correct in a real scenario. The study shows that the potentiality of  BNN that provides data patterns about rupture physics to make an additional information source for scientists studying the earthquake rupture.