Generative Adversarial Networks

Generative Adversarial Networks are a hot topic of research at the ongoing NIPS conference. GANs cast out an easy way to train the DL algorithms by slashing out the amount of data required in training with unlabelled data. Here are a few research papers on GANs.

Regularization can stabilize training of GANs

Microsoft researchers have proposed a new regularization approach to yield a stable GAN training procedure at low computational costs. Their new model overcomes the fundamental limitation of GANs occurring due to a dimensional mismatch between the model distribution and the true distribution. This results in their density ratio and the associated f-divergence to be undefined. Their paper “Stabilizing Training of Generative Adversarial Networks through Regularization” turns GAN models into reliable building blocks for deep learning. They have also used this for several datasets including image generation tasks.

AdaGAN: Boosting GAN Performance

Training GANs can at times be a hard task. They can also suffer from the problem of missing modes where the model is not able to produce examples in certain regions of the space. Google researchers have developed an iterative procedure called AdaGAN in their paper “AdaGAN: Boosting Generative Models”, an approach inspired by boosting algorithms, where many potentially weak individual predictors are greedily aggregated to form a strong composite predictor. It adds a new component into a mixture model at every step by running a GAN algorithm on a re-weighted sample. The paper also addresses the problem of missing modes.

Houdini: Generating Adversarial Examples

The generation of adversarial examples is considered as a critical milestone for evaluating and upgrading the robustness of learning in machines. Also, current methods are confined to classification tasks and are unable to alter the performance measure of the problem at hand. In order to tackle such an issue, Facebook researchers have come up with a research paper titled “Houdini: Fooling Deep Structured Prediction Models”, a novel and a flexible approach for generating adversarial examples distinctly tailormade for the final performance measure of the task taken into account (combinational and non-decomposable tasks).

Stochastic hard-attention for Memory Addressing in GANs

DeepMind researchers showcased a new method which uses stochastic hard-attention to retrieve memory content in generative models. Their paper titled “Variational memory addressing in generative models” was presented at the 2nd day of the conference and is an advancement over the popular differentiable soft-attention mechanism. Their new technique allows developers to apply variational inference to memory addressing. This leads to more precise memory lookups using target information, especially in models with large memory buffers and with many confounding entries in the memory.

Image and Video Processing

A lot of hype was also around developing sophisticated models and techniques for image and video processing. Here is a quick glance at the top presentations.

Fader Networks: Image manipulation through disentanglement

Facebook researchers have introduced Fader Networks, in their paper titled “Fader Networks: Manipulating Images by Sliding Attributes”. These fader networks use an encoder-decoder architecture to reconstruct images by disentangling their salient information and the values of particular attributes directly in a latent space. Disentanglement helps in manipulating these attributes to generate variations of pictures of faces while preserving their naturalness. This innovative approach results in much simpler training schemes and scales for manipulating multiple attributes jointly.

Visual interaction networks for Video simulation

Another paper titled “Visual interaction networks: Learning a physics simulator from video Tuesday” proposes a new neural-network model to learn physical objects without prior knowledge. Deepmind’s Visual Interaction Network is used for video analysis and is able to infer the states of multiple physical objects from just a few frames of video. It then uses these to predict object positions many steps into the future. It can also deduce the locations of invisible objects.

Transfer, Reinforcement, and Continual Learning

A lot of research is going on in the field of Transfer, Reinforcement, and Continual learning to make stable and powerful deep learning models. Here are a few research papers presented in this domain.

Two new techniques for Transfer Learning

Currently, a large set of input/output (I/O) examples are required for learning any underlying input-output mapping. By leveraging information based on the related tasks, the researchers at Microsoft have addressed the problem of data and computation efficiency of program induction. Their paper “Neural Program Meta-Induction” uses two approaches for cross-task knowledge transfer. First is Portfolio adaption, where a set of induction models is pretrained on a set of related tasks, and the best model is adapted towards the new task using transfer learning. The second one is Meta program induction, a k-shot learning approach which makes a model generalize itself to new tasks without requiring any additional training.

Hybrid Reward Architecture to solve the problem of generalization in Reinforcement Learning

A new paper from Microsoft “Hybrid Reward Architecture for Reinforcement Learning” highlights a new method to address the generalization problem faced by a typical deep RL method. Hybrid Reward Architecture (HRA) takes a decomposed reward function as the input and learns a separate value function for each component reward function. This is especially useful in domains where the optimal value function cannot easily be reduced to a low-dimensional representation. In the new approach, the overall value function is much smoother and can be easier approximated by a low-dimensional representation, enabling more effective learning.

Gradient Episodic Memory to counter catastrophic forgetting in continual learning models

Continual learning is all about improving the ability of models to solve sequential tasks without forgetting previously acquired knowledge. In the paper “Gradient Episodic Memory for Continual Learning”, Facebook researchers have proposed a set of metrics to evaluate models over a continuous series of data. These metrics characterize models by their test accuracy and the ability to transfer knowledge across tasks. They have also proposed a model for continual learning, called Gradient Episodic Memory (GEM) that reduces the problem of catastrophic forgetting. They have also experimented with variants of the MNIST and CIFAR-100 datasets to demonstrate the performance of GEM when compared to other methods.

In our next post, we will cover a selection of papers presented so far at NIPS 2017 in the areas of Predictive Modelling, Machine Translation, and more.

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