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Deep Learning with Theano

You're reading from   Deep Learning with Theano Perform large-scale numerical and scientific computations efficiently

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Product type Paperback
Published in Jul 2017
Publisher Packt
ISBN-13 9781786465825
Length 300 pages
Edition 1st Edition
Tools
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Author (1):
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Christopher Bourez Christopher Bourez
Author Profile Icon Christopher Bourez
Christopher Bourez
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Table of Contents (15) Chapters Close

Preface 1. Theano Basics 2. Classifying Handwritten Digits with a Feedforward Network FREE CHAPTER 3. Encoding Word into Vector 4. Generating Text with a Recurrent Neural Net 5. Analyzing Sentiment with a Bidirectional LSTM 6. Locating with Spatial Transformer Networks 7. Classifying Images with Residual Networks 8. Translating and Explaining with Encoding – decoding Networks 9. Selecting Relevant Inputs or Memories with the Mechanism of Attention 10. Predicting Times Sequences with Advanced RNN 11. Learning from the Environment with Reinforcement 12. Learning Features with Unsupervised Generative Networks 13. Extending Deep Learning with Theano Index

A localization network


In Spatial Transformer Networks (STN), instead of applying the network directly to the input image signal, the idea is to add a module to preprocess the image and crop it, rotate it, and scale it to fit the object, to assist in classification:

Spatial Transformer Networks

For that purpose, STNs use a localization network to predict the affine transformation parameters and process the input:

Spatial transformer networks

In Theano, differentiation through the affine transformation is automatic, we simply have to connect the localization net with the input of the classification net through the affine transformation.

First, we create a localization network not very far from the MNIST CNN model, to predict six parameters of the affine transformation:

l_in = lasagne.layers.InputLayer((None, dim, dim))
l_dim = lasagne.layers.DimshuffleLayer(l_in, (0, 'x', 1, 2))
l_pool0_loc = lasagne.layers.MaxPool2DLayer(l_dim, pool_size=(2, 2))
l_dense_loc = mnist_cnn.model(l_pool0_loc, input_dim...
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