I mentioned in my initial post “Deep Learning Frameworks Overview” that my choice of Deep Learning library is (at least for now) Theano and Lasagne combination. However, I did not use, in all my post, some most important word: **the experiment**. So, let’s assume that you have some idea and want to test it quickly. For example, what if we add to a standard CNN (omitted maxpooling for a clarity):

some extra “convolutional branch”, that is concatenated with last but one layer:

This experiment is really easy to do in (based on Theano) Lasagne. I have just added a build_modified_cnn method to a mnist example (bolded text refers to my “convolutional branch”, rest is the same as a standard build_cnn method):

def build_modified_cnn(input_var=None): l_in = lasagne.layers.InputLayer(shape=(None, 1, 28, 28), input_var=input_var) l_conv1 = lasagne.layers.Conv2DLayer( l_in, num_filters=32, filter_size=(5, 5), nonlinearity=lasagne.nonlinearities.rectify, W=lasagne.init.GlorotUniform())l_conv1A = lasagne.layers.Conv2DLayer( l_in, num_filters=32, filter_size=(10, 10), nonlinearity=lasagne.nonlinearities.rectify, W=lasagne.init.GlorotUniform())l_maxpool1A = lasagne.layers.MaxPool2DLayer(l_conv1A, pool_size=(5, 5))l_dense1A = lasagne.layers.FlattenLayer(l_maxpool1A)l_maxpool1 = lasagne.layers.MaxPool2DLayer(l_conv1, pool_size=(2, 2)) l_conv2 = lasagne.layers.Conv2DLayer( l_maxpool1, num_filters=32, filter_size=(5, 5), nonlinearity=lasagne.nonlinearities.rectify) l_maxpool2 = lasagne.layers.MaxPool2DLayer(l_conv2, pool_size=(2, 2)) l_dense1 = lasagne.layers.DenseLayer( lasagne.layers.dropout(l_maxpool2, p=.5), num_units=256, nonlinearity=lasagne.nonlinearities.rectify)l_concat = lasagne.layers.ConcatLayer([l_dense1, l_dense1A])l_dense2 = lasagne.layers.DenseLayer( lasagne.layers.dropout(l_concat, p=.5), num_units=10, nonlinearity=lasagne.nonlinearities.softmax) return l_dense2

We see here some standard layers such as Conv2DLayer and MaxPool2DLayer and less standard however self-explanatory ones: FlattenLayer and ConcatLayer. Some results of the test on mnist dataset:

Type | Epoch | Accuracy | Time |

Standard CNN | 1 | 56.75 % |
6.767s |

Standard CNN | 30 | 96.76 % | 6.923s |

Modified CNN | 1 | 72.51 % |
9.552s |

Modified CNN | 30 | 96.03 % | 9.592s |

Not this time. My modification made a significant progress, if we look only at first epoch. However, in general, it learns slower than a standard one. But to see it, **I needed only a few minutes of coding** – and this is a true power of Theano and Theano-based libs!