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 Deep Learning


Convolutional Neural Networks Demystified: A Matched Filtering Perspective Based Tutorial

arXiv.org Artificial Intelligence

Deep Neural Networks (DNN) and especially Convolutional Neural Networks (CNN) are a de-facto standard for the analysis of large volumes of signals and images. Yet, their development and underlying principles have been largely performed in an ad-hoc and black box fashion. To help demystify CNNs, we revisit their operation from first principles and a matched filtering perspective. We establish that the convolution operation within CNNs, their very backbone, represents a matched filter which examines the input signal/image for the presence of pre-defined features. This perspective is shown to be physically meaningful, and serves as a basis for a step-by-step tutorial on the operation of CNNs, including pooling, zero padding, various ways of dimensionality reduction. Starting from first principles, both the feed-forward pass and the learning stage (via back-propagation) are illuminated in detail, both through a worked-out numerical example and the corresponding visualizations. It is our hope that this tutorial will help shed new light and physical intuition into the understanding and further development of deep neural networks.


Unsupervised Dense Deformation Embedding Network for Template-Free Shape Correspondence

arXiv.org Artificial Intelligence

Shape correspondence from 3D deformation learning has attracted appealing academy interests recently. Nevertheless, current deep learning based methods require the supervision of dense annotations to learn per-point translations, which severely overparameterize the deformation process. Moreover, they fail to capture local geometric details of original shape via global feature embedding. To address these challenges, we develop a new Unsupervised Dense Deformation Embedding Network (i.e., UD^2E-Net), which learns to predict deformations between non-rigid shapes from dense local features. Since it is non-trivial to match deformation-variant local features for deformation prediction, we develop an Extrinsic-Intrinsic Autoencoder to frst encode extrinsic geometric features from source into intrinsic coordinates in a shared canonical shape, with which the decoder then synthesizes corresponding target features. Moreover, a bounded maximum mean discrepancy loss is developed to mitigate the distribution divergence between the synthesized and original features. To learn natural deformation without dense supervision, we introduce a coarse parameterized deformation graph, for which a novel trace and propagation algorithm is proposed to improve both the quality and effciency of the deformation. Our UD^2E-Net outperforms state-of-the-art unsupervised methods by 24% on Faust Inter challenge and even supervised methods by 13% on Faust Intra challenge.


Understanding Attention in Machine Reading Comprehension

arXiv.org Artificial Intelligence

Achieving human-level performance on some of Machine Reading Comprehension (MRC) datasets is no longer challenging with the help of powerful Pre-trained Language Models (PLMs). However, the internal mechanism of these artifacts still remains unclear, placing an obstacle for further understanding these models. This paper focuses on conducting a series of analytical experiments to examine the relations between the multi-head self-attention and the final performance, trying to analyze the potential explainability in PLM-based MRC models. We perform quantitative analyses on SQuAD (English) and CMRC 2018 (Chinese), two span-extraction MRC datasets, on top of BERT, ALBERT, and ELECTRA in various aspects. We discover that {\em passage-to-question} and {\em passage understanding} attentions are the most important ones, showing strong correlations to the final performance than other parts. Through visualizations and case studies, we also observe several general findings on the attention maps, which could be helpful to understand how these models solve the questions.


A spatio-temporal LSTM model to forecast across multiple temporal and spatial scales

arXiv.org Machine Learning

This paper presents a novel spatio-temporal LSTM (SPATIAL) architecture for time series forecasting applied to environmental datasets. The framework was evaluated across multiple sensors and for three different oceanic variables: current speed, temperature, and dissolved oxygen. Network implementation proceeded in two directions that are nominally separated but connected as part of a natural environmental system -- across the spatial (between individual sensors) and temporal components of the sensor data. Data from four sensors sampling current speed, and eight measuring both temperature and dissolved oxygen evaluated the framework. Results were compared against RF and XGB baseline models that learned on the temporal signal of each sensor independently by extracting the date-time features together with the past history of data using sliding window matrix. Results demonstrated ability to accurately replicate complex signals and provide comparable performance to state-of-the-art benchmarks. Notably, the novel framework provided a simpler pre-processing and training pipeline that handles missing values via a simple masking layer. Enabling learning across the spatial and temporal directions, this paper addresses two fundamental challenges of ML applications to environmental science: 1) data sparsity and the challenges and costs of collecting measurements of environmental conditions such as ocean dynamics, and 2) environmental datasets are inherently connected in the spatial and temporal directions while classical ML approaches only consider one of these directions. Furthermore, sharing of parameters across all input steps makes SPATIAL a fast, scalable, and easily-parameterized forecasting framework.


Deep learning based dictionary learning and tomographic image reconstruction

arXiv.org Machine Learning

This work presents an approach for image reconstruction in clinical low-dose tomography that combines principles from sparse signal processing with ideas from deep learning. First, we describe sparse signal representation in terms of dictionaries from a statistical perspective and interpret dictionary learning as a process of aligning distribution that arises from a generative model with empirical distribution of true signals. As a result we can see that sparse coding with learned dictionaries resembles a specific variational autoencoder, where the decoder is a linear function and the encoder is a sparse coding algorithm. Next, we show that dictionary learning can also benefit from computational advancements introduced in the context of deep learning, such as parallelism and as stochastic optimization. Finally, we show that regularization by dictionaries achieves competitive performance in computed tomography (CT) reconstruction comparing to state-of-the-art model based and data driven approaches.


Modeling Item Response Theory with Stochastic Variational Inference

arXiv.org Machine Learning

Item Response Theory (IRT) is a ubiquitous model for understanding human behaviors and attitudes based on their responses to questions. Large modern datasets offer opportunities to capture more nuances in human behavior, potentially improving psychometric modeling leading to improved scientific understanding and public policy. However, while larger datasets allow for more flexible approaches, many contemporary algorithms for fitting IRT models may also have massive computational demands that forbid real-world application. To address this bottleneck, we introduce a variational Bayesian inference algorithm for IRT, and show that it is fast and scalable without sacrificing accuracy. Applying this method to five large-scale item response datasets from cognitive science and education yields higher log likelihoods and higher accuracy in imputing missing data than alternative inference algorithms. Using this new inference approach we then generalize IRT with expressive Bayesian models of responses, leveraging recent advances in deep learning to capture nonlinear item characteristic curves (ICC) with neural networks. Using an eigth-grade mathematics test from TIMSS, we show our nonlinear IRT models can capture interesting asymmetric ICCs. The algorithm implementation is open-source, and easily usable.


OpenAI Codex translates english into code

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Codex is a descendant of GPT-3 – its training data contains both natural language and billions of lines of source code from publicly available sources, including code in public GitHub repositories. "We see this as a tool to multiply programmers," OpenAI's CTO and co-founder Greg Brockman told The Verge. "Programming has two parts to it: you have'think hard about a problem and try to understand it,' and'map those small pieces to existing code, whether it's a library, a function, or an API.'" The second part is tedious, he says, but it's what Codex is best at. "It takes people who are already programmers and removes the drudge work."


Convolutional Neural Networks - AI Summary

#artificialintelligence

Research by Hubel and Wiesel [2,3] analyzed the striate cortex of cats and monkeys, revealing two key findings that would come to heavily influence Fukushima's work [1]. The next significant implementation of a convolution neural network was LeNet-5 proposed in 1999 by Le Cun et al. in their work "Object Recognition with Gradient Based Learning'' [4]. Their proposed network, LeNet-5 performed well on the MNIST data set and was shown to do better than state of the art (at the time) SVMs and K-nearest neighbor based approaches. Their final implementation outperformed other state of the art image classification algorithms with error rates which were 10% lower than its competitors on the ImageNet dataset. This application of a discrete convolution precisely represents local receptive fields observed by Hubel and Wiesel [2,3] and implemented in early CNNs by Fukushima and Le Cun [1,4]. Research by Hubel and Wiesel [2,3] analyzed the striate cortex of cats and monkeys, revealing two key findings that would come to heavily influence Fukushima's work [1]. The next significant implementation of a convolution neural network was LeNet-5 proposed in 1999 by Le Cun et al. in their work "Object Recognition with Gradient Based Learning'' [4].


Convolutional Neural Network

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Today the topic of discussion is Convolutional Neural Network(CNN). We earlier discussed the Feedforward Neural Network where an output of one linear layer was fed to the next layer with an activation layer sandwiched between the two. Here is the link to the article. The CNN is good at identifying the images and classifying them in different classes. Basically a 2D convolution is the sliding of one smaller matrix over the other bigger matrix.


Top GPUs for Deep Learning

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ZOTAC GeForce GTX 1070, Graphics cards are the most advanced gaming GPUs ever created. They're driven by the new NVIDIA Pascal Architecture and Latest technologies to deliver incredible new levels of gaming and immersive HR. NVIDIA GeForce RTX 2060, The Nvidia RTX 2060 is powerful enough to keep frame rates well north of 60fps in Full HD gaming, which is great for deep learning processing.