Sequential training of GANs against GAN-classifiers reveals correlated "knowledge gaps" present among independently trained GAN instances

Arkanath Pathak, Nicholas Dufour

IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 2023

Modern Generative Adversarial Networks (GANs) generate realistic images remarkably well. Previous work has demonstrated the feasibility of "GAN-classifiers" that are distinct from the co-trained discriminator, and operate on images generated from a frozen GAN. That such classifiers work at all affirms the existence of "knowledge gaps" (out-of-distribution artifacts across samples) present in GAN training. We iteratively train GAN-classifiers and train GANs that "fool" the classifiers (in an attempt to fill the knowledge gaps), and examine the effect on GAN training dynamics, output quality, and GAN-classifier generalization. We investigate two settings, a small DCGAN architecture trained on low dimensional images (MNIST), and StyleGAN2, a SOTA GAN architecture trained on high dimensional images (FFHQ). We find that the DCGAN is unable to effectively fool a held-out GAN-classifier without compromising the output quality. However, StyleGAN2 can fool held-out classifiers with no change in output quality, and this effect persists over multiple rounds of GAN/classifier training which appears to reveal an ordering over optima in the generator parameter space. Finally, we study different classifier architectures and show that the architecture of the GAN-classifier has a strong influence on the set of its learned artifacts.

High Fidelity Video Prediction with Large Stochastic Recurrent Neural Networks

Ruben Villegas, Arkanath Pathak, Harini Kannan, Dumitru Erhan, Quoc V. Le, Honglak Lee

Neural Information Processing Systems (NeurIPS), 2019

Predicting future video frames is extremely challenging, as there are many factors of variation that make up the dynamics of how frames change through time. Previously proposed solutions require complex inductive biases inside network architectures with highly specialized computation, including segmentation masks, optical flow, and foreground and background separation. In this work, we question if such handcrafted architectures are necessary and instead propose a different approach: finding minimal inductive bias for video prediction while maximizing network capacity. We investigate this question by performing the first large-scale empirical study and demonstrate state-of-the-art performance by learning large models on three different datasets: one for modeling object interactions, one for modeling human motion, and one for modeling car driving.

Learning 6-DOF Grasping Interaction via Deep Geometry-Aware 3D Representations

Xinchen Yan, Mohi Khansari, Yunfei Bai, Jasmine Hsu, Arkanath Pathak, Arbhinav Gupta, James Davidson, Honglak Lee

IEEE International Conference on Robotics and Automation (ICRA), 2018

This paper focuses on the problem of learning 6-DOF grasping with a parallel jaw gripper in simulation. Our key idea is constraining and regularizing grasping interaction learning through 3D geometry prediction. We introduce a deep geometry-aware grasping network (DGGN) that decomposes the learning into two steps. First, we learn to build mental geometry-aware representation by reconstructing the scene (i.e., 3D occupancy grid) from RGBD input via generative 3D shape modeling. Second, we learn to predict grasping outcome with its internal geometry-aware representation. The learned outcome prediction model is used to sequentially propose grasping solutions via analysis-by-synthesis optimization. Our contributions are fourfold: (1) To best of our knowledge, we are presenting for the first time a method to learn a 6-DOF grasping net from RGBD input; (2) We build a grasping dataset from demonstrations in virtual reality with rich sensory and interaction annotations. This dataset includes 101 everyday objects spread across 7 categories, additionally, we propose a data augmentation strategy for effective learning; (3) We demonstrate that the learned geometry-aware representation leads to about 10% relative performance improvement over the baseline CNN on grasping objects from our dataset. (4) We further demonstrate that the model generalizes to novel viewpoints and object instances.

A Two-Phase Approach Towards Identifying Argument Structure in Natural Language

Arkanath Pathak, Pawan Goyal, Plaban Bhowmick

3rd Workshop on Natural Language Processing Techniques for Educational Applications (NLPTEA), 2016

We propose a new approach for extracting argument structure from natural language texts that contain an underlying argument. Our approach comprises of two phases: Score Assignment and Structure Prediction. The Score Assignment phase trains models to classify relations between argument units (Support, Attack or Neutral). To that end, different training strategies have been explored. We identify different linguistic and lexical features for training the classifiers. Through ablation study, we observe that our novel use of word-embedding features is most effective for this task. The Structure Prediction phase makes use of the scores from the Score Assignment phase to arrive at the optimal structure. We perform experiments on three argumentation datasets, namely, AraucariaDB, Debatepedia and Wikipedia. We also propose two baselines and observe that the proposed approach outperforms baseline systems for the final task of Structure Prediction.

Clustering of Mixed Data by Integrating Fuzzy, Probabilistic, and Collaborative Clustering Framework

Arkanath Pathak, Nikhil R. Pal

International Journal of Fuzzy Systems (IJFS), 2016

Clustering of numerical data is a very well researched problem and so is clustering of categorical data. However, when it comes to clustering of data with mixed attributes, the literature is not that rich. For numerical data, fuzzy clustering, in particular, the fuzzy c-means (FCM), is a very effective and popular algorithm, while for categorical data, use of mixture model is quite popular. In this paper, we propose a novel framework for clustering of mixed data which contains both numerical and categorical attributes. Our objective is to find the cluster substructures that are common to both the categorical and numerical data. Our formulation is inspired by the FCM algorithm (for dealing with numerical data), mixture models (for dealing with categorical data), and the collaborative clustering framework for aggregation of the two—it is an integrated approach that judiciously uses all three components. We use our algorithm on a few commonly used datasets and compare our results with those by some state of the art methods.