Deep Learning
Stochastic Blockmodels meet Graph Neural Networks
Mehta, Nikhil, Carin, Lawrence, Rai, Piyush
Stochastic blockmodels (SBM) and their variants, $e.g.$, mixed-membership and overlapping stochastic blockmodels, are latent variable based generative models for graphs. They have proven to be successful for various tasks, such as discovering the community structure and link prediction on graph-structured data. Recently, graph neural networks, $e.g.$, graph convolutional networks, have also emerged as a promising approach to learn powerful representations (embeddings) for the nodes in the graph, by exploiting graph properties such as locality and invariance. In this work, we unify these two directions by developing a \emph{sparse} variational autoencoder for graphs, that retains the interpretability of SBMs, while also enjoying the excellent predictive performance of graph neural nets. Moreover, our framework is accompanied by a fast recognition model that enables fast inference of the node embeddings (which are of independent interest for inference in SBM and its variants). Although we develop this framework for a particular type of SBM, namely the \emph{overlapping} stochastic blockmodel, the proposed framework can be adapted readily for other types of SBMs. Experimental results on several benchmarks demonstrate encouraging results on link prediction while learning an interpretable latent structure that can be used for community discovery.
Convolutional Poisson Gamma Belief Network
Wang, Chaojie, Chen, Bo, Xiao, Sucheng, Zhou, Mingyuan
For text analysis, one often resorts to a lossy representation that either completely ignores word order or embeds each word as a low-dimensional dense feature vector. In this paper, we propose convolutional Poisson factor analysis (CPFA) that directly operates on a lossless representation that processes the words in each document as a sequence of high-dimensional one-hot vectors. To boost its performance, we further propose the convolutional Poisson gamma belief network (CPGBN) that couples CPFA with the gamma belief network via a novel probabilistic pooling layer. CPFA forms words into phrases and captures very specific phrase-level topics, and CPGBN further builds a hierarchy of increasingly more general phrase-level topics. For efficient inference, we develop both a Gibbs sampler and a Weibull distribution based convolutional variational auto-encoder. Experimental results demonstrate that CPGBN can extract high-quality text latent representations that capture the word order information, and hence can be leveraged as a building block to enrich a wide variety of existing latent variable models that ignore word order.
A Statistically Principled and Computationally Efficient Approach to Speech Enhancement using Variational Autoencoders
Pariente, Manuel, Deleforge, Antoine, Vincent, Emmanuel
Recent studies have explored the use of deep generative models of speech spectra based of variational autoencoders (VAEs), combined with unsupervised noise models, to perform speech enhancement. These studies developed iterative algorithms involving either Gibbs sampling or gradient descent at each step, making them computationally expensive. This paper proposes a variational inference method to iteratively estimate the power spectrogram of the clean speech. Our main contribution is the analytical derivation of the variational steps in which the en-coder of the pre-learned VAE can be used to estimate the varia-tional approximation of the true posterior distribution, using the very same assumption made to train VAEs. Experiments show that the proposed method produces results on par with the afore-mentioned iterative methods using sampling, while decreasing the computational cost by a factor 36 to reach a given performance .
What is Geometric Deep Learning?
There are various types of graphs, each with a set of rules, properties, and possible actions. Graph theory is the study of graphs and what we can learn from them. This will be covered in the next part of this series. For a concrete example of how Graph Learning can greatly improve existing machine learning tasks we can take a look at the computational sciences. One of the bottlenecks in computational chemistry, biology, and physics is the representation concepts, entities, and interactions.
Anthropology Technology Conference 2019 at The Watershed in October -
You might think that anthropology and AI is an odd pairing. But in a 2017 article in WIRED, journalist James Temperton wrote, "For DeepMind to realise its ambition of cracking general intelligence, it needs an interdisciplinary approach to AI". As DeepMind co-founder Mustafa Suleyman explained in the same article, "We need to have in-house the very best anthropologists, sociologistsโฆspecialists on bias and discrimination in machine learning systems, working with both our researchers and applied software development teams so that they can give them feedback and guidance and introduce them to new modes of critical thinking". So in the spirit of cross-disciplinary collaboration, around 300 technologists working in AI (machine learning, data science, robotics, AI) and anthropologists and sociologists from around the world will come together at the Watershed on Bristol's historic harbourside to discuss human-centred AI. One of the keynotes, Dr Julien Cornebise, is from Element AI.
Generalizable Deep Reinforcement Learning
Transfer learning is all the rage in the machine learning community these days. Transfer learning serves as the basis for many of the managed AutoML services that Google, Salesforce, IBM, and Azure provide. It now figures prominently in the latest NLP research -- appearing in Google's Bidirectional Encoder Representations from Transformers (BERT) model and in Sebastian Ruder and Jeremy Howard's Universal Language Model Fine-tuning for Text Classification (ULMFIT). As Sebastian writes in his blog post, 'NLP's ImageNet moment has arrived': We're also starting to see examples of neural networks that can handle multiple tasks using transfer learning across domains. Paras Chopra has an excellent tutorial for one PyTorch network that can conduct an image search based on a textual description, search for similar images and words, and write captions for images (link to his post below). The main question at hand is: could transfer learning have applications within reinforcement learning?
Worlds first AI computer for railway market โ available now!
Currently this platform sets standards in AI performance and is paving the way for future deep learning applications. The AI railway computer is fully EN50155 compliant. As a result, the device combines the best of both worlds. The AI railway computer is deployed wherever AI and Edge Computing meet. The AI in-vehicle computer allows you to improve safety and economic efficiency on the rails.
Enforcing Statistical Constraints in Generative Adversarial Networks for Modeling Chaotic Dynamical Systems
Wu, Jin-Long, Kashinath, Karthik, Albert, Adrian, Chirila, Dragos, Prabhat, null, Xiao, Heng
Simulating complex physical systems often involves solving partial differential equations (PDEs) with some closures due to the presence of multi-scale physics that cannot be fully resolved. Therefore, reliable and accurate closure models for unresolved physics remains an important requirement for many computational physics problems, e.g., turbulence simulation. Recently, several researchers have adopted generative adversarial networks (GANs), a novel paradigm of training machine learning models, to generate solutions of PDEs-governed complex systems without having to numerically solve these PDEs. However, GANs are known to be difficult in training and likely to converge to local minima, where the generated samples do not capture the true statistics of the training data. In this work, we present a statistical constrained generative adversarial network by enforcing constraints of covariance from the training data, which results in an improved machine-learning-based emulator to capture the statistics of the training data generated by solving fully resolved PDEs. We show that such a statistical regularization leads to better performance compared to standard GANs, measured by (1) the constrained model's ability to more faithfully emulate certain physical properties of the system and (2) the significantly reduced (by up to 80%) training time to reach the solution. We exemplify this approach on the Rayleigh-Benard convection, a turbulent flow system that is an idealized model of the Earth's atmosphere. With the growth of high-fidelity simulation databases of physical systems, this work suggests great potential for being an alternative to the explicit modeling of closures or parameterizations for unresolved physics, which are known to be a major source of uncertainty in simulating multi-scale physical systems, e.g., turbulence or Earth's climate.
Spectral Analysis of Kernel and Neural Embeddings: Optimization and Generalization
Jorge, Emilio, Chehreghani, Morteza Haghir, Dubhashi, Devdatt
Kernel methods are one of by a spectral analysis of representations corresponding the pillars of machine learning, as they give us a flexible to kernel and neural embeddings. They framework to model complex functional relationships in a showed that in a simple single layer network, the principled way and also come with well-established statistical alignment of the labels to the eigenvectors of the properties and theoretical guarantees. The interplay of corresponding Gram matrix determines both the kernels and data labellings has been addressed before, for convergence of the optimization during training example in the work on kernel-target alignment (Cristianini as well as the generalization properties. We show et al., 2001). Recently, (Belkin et al., 2018) also make the quantitatively that kernel and neural representations case that progress on understanding deep learning is unlikely improve both optimization and generalization.
Winograd Convolution for DNNs: Beyond linear polinomials
Barabasz, Barbara, Gregg, David
We investigated a wider range of Winograd family convolution algorithms for Deep Neural Network. We presented the explicit Winograd convolution algorithm in general case (used the polynomials of the degrees higher than one). It allows us to construct more different versions in the aspect of performance than commonly used Winograd convolution algorithms and improve the accuracy and performance of convolution computations. We found that in $fp16$ this approach gives us better accuracy of image recognition while keeps the same number of general multiplications computed per single output point as the commonly used Winograd algorithm for a kernel of the size $3 \times 3$ and output size equal to $4 \times 4$. We demonstrated that in $bf16$ it is possible to perform the convolution computation faster keeping the accuracy of image recognition the same as for direct convolution method. We tested our approach for a subset of $2000$ images from Imaginet validation set. We present the results for three precision of computations $fp32$, $fp16$ and $bf16$.