https://github.com/raghakot/keras-resnet

Residual networks implementation using Keras-1.0 functional API
https://github.com/raghakot/keras-resnet

deep-learning keras resnet

Last synced: 6 days ago
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Residual networks implementation using Keras-1.0 functional API

• Host: GitHub
• URL: https://github.com/raghakot/keras-resnet
• Owner: raghakot
• License: other
• Created: 2016-04-18T02:43:11.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2021-01-12T11:01:26.000Z (almost 4 years ago)
• Last Synced: 2024-11-30T13:04:14.515Z (13 days ago)
• Topics: deep-learning, keras, resnet
• Language: Python
• Size: 1.61 MB
• Stars: 1,386
• Watchers: 53
• Forks: 615
• Open Issues: 24
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-image-classification - unofficial-keras : https://github.com/raghakot/keras-resnet
• awesome-image-classification - unofficial-keras : https://github.com/raghakot/keras-resnet

README

        
# keras-resnet

[![Build Status](https://travis-ci.org/raghakot/keras-resnet.svg?branch=master)](https://travis-ci.org/raghakot/keras-resnet)

[![license](https://img.shields.io/github/license/mashape/apistatus.svg?maxAge=2592000)](https://github.com/raghakot/keras-resnet/blob/master/LICENSE)

Residual networks implementation using Keras-1.0 functional API, that works with 

both theano/tensorflow backend and 'th'/'tf' image dim ordering.

### The original articles

 * [Deep Residual Learning for Image Recognition](http://arxiv.org/abs/1512.03385) (the 2015 ImageNet competition winner)

 * [Identity Mappings in Deep Residual Networks](http://arxiv.org/abs/1603.05027)

### Residual blocks

The residual blocks are based on the new improved scheme proposed in [Identity Mappings in Deep Residual Networks](http://arxiv.org/abs/1603.05027) as shown in figure (b)

![Residual Block Scheme](images/residual_block.png?raw=true "Residual Block Scheme")

Both bottleneck and basic residual blocks are supported. To switch them, simply provide the block function [here](https://github.com/raghakot/keras-resnet/blob/master/resnet.py#L109)

### Code Walkthrough

The architecture is based on 50 layer sample (snippet from paper)

![Architecture Reference](images/architecture.png?raw=true "Architecture Reference")

There are two key aspects to note here

 1. conv2_1 has stride of (1, 1) while remaining conv layers has stride (2, 2) at the beginning of the block. This fact is expressed in the following [lines](https://github.com/raghakot/keras-resnet/blob/master/resnet.py#L63-L65).

 2. At the end of the first skip connection of a block, there is a disconnect in num_filters, width and height at the merge layer. This is addressed in [`_shortcut`](https://github.com/raghakot/keras-resnet/blob/master/resnet.py#L41) by using `conv 1X1` with an appropriate stride.

 For remaining cases, input is directly merged with residual block as identity.

### ResNetBuilder factory

- Use ResNetBuilder [build](https://github.com/raghakot/keras-resnet/blob/master/resnet.py#L135-L153) methods to build standard ResNet architectures with your own input shape. It will auto calculate paddings and final pooling layer filters for you.

- Use the generic [build](https://github.com/raghakot/keras-resnet/blob/master/resnet.py#L99) method to setup your own architecture.

### Cifar10 Example

Includes cifar10 training example. Achieves ~86% accuracy using Resnet18 model.

![cifar10_convergence](images/convergence.png?raw=true "Convergence on cifar10")

Note that ResNet18 as implemented doesn't really seem appropriate for CIFAR-10 as the last two residual stages end up 

as all 1x1 convolutions from downsampling (stride). This is worse for deeper versions. A smaller, modified ResNet-like 

architecture achieves ~92% accuracy (see [gist](https://gist.github.com/JefferyRPrice/c1ecc3d67068c8d9b3120475baba1d7e)).