Friday, July 7, 2017

Milestones of Deep Learning

Deep Learning has been around for about a decade now. We talked about how Deep Learning evolved through Artificial Intelligence, and Machine Learning (See "What is Deep Learning?"). Since its inception, Deep Learning has taken the world by storm due to its success. Here are some of the more significant achievements of Deep Learning throughout the years,

AlexNet - 2012

The AlexNet Architecture
The AlexNet Architecture (Image from the research paper)

  • Proved that Convolutional Neural Networks actually works. AlexNet - and its research paper "ImageNet Classification with Deep Convolutional Neural Networks" by Alex Krizhevsky, Ilya Sutskever, and Geoffrey E. Hinton - is commonly considered as what brought Deep Learning in to the mainstream.
  • Won 2012 ILSVRC (ImageNet Large-Scale Visual Recognition Challenge) with 15.4% error rate. (For reference, the 2nd best entry at ILSVRC had 26.2% error rate).
  • 8 layers: 5 convolutional, 3 fully connected.
  • Used ReLU for the non-linearity function rather than the conventional tanh function used until then.
  • Introduced the use of Dropout Layers, and Data Augmentation to overcome overfitting.
Research Paper: ImageNet Classification with Deep Convolutional Neural Networks - Alex Krizhevsky, Ilya Sutskever, Geoffrey E. Hinton

ZF Net - 2013

The ZF Net Architecture
The ZF Net Architecture (Image from the research paper)

  • Winner of  ILSVRC 2013 with an error rate of 11.2%.
  • Similar to the AlexNet architecture, with some tweaks and fine tuning to improve the performance.
  • Introduced the Deconvolutional Network (a.k.a. DeConvNet), a visualization technique to view the inner workings of a CNN.
Research Paper: Visualizing and Understanding Convolutional Networks - Matthew D. Zeiler, Rob Fergus

VGG Net - 2014

The VGG Net Architecture
The VGG Net Architecture (Image from the Keras Blog)

  • Won the "Classification+localization" category of the ILSVRC 2014 (Not the overall winner), with an error rate of 7.3%.
  • The VGG architecture worked well with both image classification and localization. 
  • 19 Layer network, with 3x3 filters. (Compared to 11x11 filters of AlexNet, and 7x7 filters of ZF Net).
  • Proved that simple deep structures works for hierarchical feature extraction.
Research Paper: Very Deep Convolutional Networks for Large-scale Image Recognition - Karen Simonyan, Andrew Zisserman

GoogLeNet - 2014/2015

The GoogLeNet Architecture
The GoogLeNet Architecture (Image from the research paper)

  • The winner of ILSVRC 2014 with an error rate of 6.7%.
  • Introduced the Inception Module, which emphasized that the layers of a CNN doesn't always have to be stacked up sequentially.

The Inception Module
The Inception Module (Image from the research paper)

  • 22 blocks of layers (over 100 layers when considered individually).
  • No Fully connected layers.
  • Proved that optimized non-sequential structures may work better than sequential ones.
Research Paper: Going Deeper with Convolutions - Christian Szegedy, Wei Liu, Yangqing Jia, Pierre Sermanet, Scott Reed, Dragomir Anguelov, Dumitru Erhan, Vincent Vanhoucke, Andrew Rabinovich, Google Inc., University of North Carolina, Chapel Hill, University of Michigan, Ann Arbor, Magic Leap Inc.

Microsoft ResNet - 2015

The ResNet Architecture
The ResNet Architecture (Image from the research paper)

  • Won ILSVRC 2015.
  • With an error rate of 3.6%, the ResNet has a higher accuracy than a human (A typical human is said to have an error rate of about 5-10%).
  • Ultra-deep (quoting the authors) architecture with 152 layers.
  • Introduced the Residual Block, to reduce overfitting.

The Residual Block
The Residual Block (Image from the research paper)

Research Paper: Deep Residual Learning for Image Recognition - Kaiming He, Xiangyu Zhang, Shaoqing Ren, Jian Sun, Microsoft Research

With Deep Learning models starting to surpass human abilities, we can be sure to see more interesting Deep Learning models, and achievements in the coming years.

Is Deep Learning just CNNs?

Now, looking back at our list above, you might be wondering whether "Deep Learning" is just Convolutional Neural Networks.


Actually, all of the following models are considered Deep Learning.
  • Convolutional Neural Networks
  • Deep Boltzmann Machine
  • Deep Belief Networks
  • Stacked Autoencoders
But, CNNs are the most 'defined' - and addressing more relatable problem spaces - in the Deep Learning field, at least at the moment. But, keep in mind that CNNs are not the whole picture of Deep Learning.

Related posts:
What is Deep Learning?

Related links:

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