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Chengxi Ye

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5

AAAI Conference 2022 Conference Paper

Exploiting Invariance in Training Deep Neural Networks

  • Chengxi Ye
  • Xiong Zhou
  • Tristan McKinney
  • Yanfeng Liu
  • Qinggang Zhou
  • Fedor Zhdanov

Inspired by two basic mechanisms in animal visual systems, we introduce a feature transform technique that imposes invariance properties in the training of deep neural networks. The resulting algorithm requires less parameter tuning, trains well with an initial learning rate 1. 0, and easily generalizes to different tasks. We enforce scale invariance with local statistics in the data to align similar samples at diverse scales. To accelerate convergence, we enforce a GL(n)-invariance property with global statistics extracted from a batch such that the gradient descent solution should remain invariant under basis change. Profiling analysis shows our proposed modifications takes ∼ 5% of the computations of the underlying convolution layer. Tested on convolutional networks and transformer networks, our proposed technique requires fewer iterations to train, surpasses all baselines by a large margin, seamlessly works on both small and large batch size training, and applies to different computer vision and language tasks.

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ICLR Conference 2020 Conference Paper

Network Deconvolution

  • Chengxi Ye
  • Matthew S. Evanusa
  • Hua He
  • Anton Mitrokhin
  • Tom Goldstein
  • James A. Yorke
  • Cornelia Fermüller
  • Yiannis Aloimonos

Convolution is a central operation in Convolutional Neural Networks (CNNs), which applies a kernel to overlapping regions shifted across the image. However, because of the strong correlations in real-world image data, convolutional kernels are in effect re-learning redundant data. In this work, we show that this redundancy has made neural network training challenging, and propose network deconvolution, a procedure which optimally removes pixel-wise and channel-wise correlations before the data is fed into each layer. Network deconvolution can be efficiently calculated at a fraction of the computational cost of a convolution layer. We also show that the deconvolution filters in the first layer of the network resemble the center-surround structure found in biological neurons in the visual regions of the brain. Filtering with such kernels results in a sparse representation, a desired property that has been missing in the training of neural networks. Learning from the sparse representation promotes faster convergence and superior results without the use of batch normalization. We apply our network deconvolution operation to 10 modern neural network models by replacing batch normalization within each. Extensive experiments show that the network deconvolution operation is able to deliver performance improvement in all cases on the CIFAR-10, CIFAR-100, MNIST, Fashion-MNIST, Cityscapes, and ImageNet datasets.

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IROS Conference 2020 Conference Paper

Unsupervised Learning of Dense Optical Flow, Depth and Egomotion with Event-Based Sensors

  • Chengxi Ye
  • Anton Mitrokhin
  • Cornelia Fermüller
  • James A. Yorke
  • Yiannis Aloimonos

We present an unsupervised learning pipeline for dense depth, optical flow and egomotion estimation for autonomous driving applications, using the event-based output of the Dynamic Vision Sensor (DVS) as input. The backbone of our pipeline is a bioinspired encoder-decoder neural network architecture - ECN. To train the pipeline, we introduce a covariance normalization technique which resembles the lateral inhibition mechanism found in animal neural systems. Our work is the first monocular pipeline that generates dense depth and optical flow from sparse event data only, and is able to transfer from day to night scenes without any additional training. The network works in self-supervised mode and has just 150k parameters. We evaluate our pipeline on the MVSEC self driving dataset and present results for depth, optical flow and and egomotion estimation. Thanks to the efficient design, we are able to achieve inference rates of 300 FPS on a single Nvidia 1080Ti GPU. Our experiments demonstrate significant improvements upon works that used deep learning on event data, as well as the ability to perform well during both day and night.

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IROS Conference 2019 Conference Paper

EV-IMO: Motion Segmentation Dataset and Learning Pipeline for Event Cameras

  • Anton Mitrokhin
  • Chengxi Ye
  • Cornelia Fermüller
  • Yiannis Aloimonos
  • Tobi Delbruck

We present the first event-based learning approach for motion segmentation in indoor scenes and the first event-based dataset – EV-IMO– which includes accurate pixel-wise motion masks, egomotion and ground truth depth. Our approach is based on an efficient implementation of the SfM learning pipeline using a low parameter neural network architecture on event data. In addition to camera egomotion and a dense depth map, the network estimates independently moving object segmentation at the pixel-level and computes per-object 3D translational velocities of moving objects. We also train a shallow network with just 40k parameters, which is able to compute depth and egomotion. Our EV-IMO dataset features 32 minutes of indoor recording with up to 3 fast moving objects in the camera field of view. The objects and the camera are tracked using a VICON ® motion capture system. By 3D scanning the room and the objects, ground truth of the depth map and pixel-wise object masks are obtained. We then train and evaluate our learning pipeline on EV-IMO and demonstrate that it is well suited for scene constrained robotics applications. SUPPLEMENTARY MATERIAL The supplementary video, code, trained models, appendix and a dataset will be made available at http://prg.cs.umd.edu/EV-IMO.html.

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ICRA Conference 2017 Conference Paper

What can i do around here? Deep functional scene understanding for cognitive robots

  • Chengxi Ye
  • Yezhou Yang
  • Ren Mao
  • Cornelia Fermüller
  • Yiannis Aloimonos

For robots that have the capability to interact with the physical environment through their end effectors, understanding the surrounding scenes is not merely a task of image classification or object recognition. To perform actual tasks, it is critical for the robot to have a functional understanding of the visual scene. Here, we address the problem of localization and recognition of functional areas in an arbitrary indoor scene, formulated as a two-stage deep learning based detection pipeline. A new scene functionality testing-bed, which is compiled from two publicly available indoor scene datasets, is used for evaluation. Our method is evaluated quantitatively on the new dataset, demonstrating the ability to perform efficient recognition of functional areas from arbitrary indoor scenes. We also demonstrate that our detection model can be generalized to novel indoor scenes by cross validating it with images from two different datasets.

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