# Neural Network [grade 8]

# Convolution with CNN

## grade 8: Convolution with CNN

There’s a very comprehensive introduction on convolutional neural networks from cs231n.

We will focus on how to implement a cnn from scratch (with numpy), and apply it on mnist dataset.

Key steps for implementation:

- On the feed forward, the convolutional operation;
- On the back propagation, there are couple of items significantly differentiate with deep neural network we introduced before:
- the pooling layer, which does not have an activate function like relu/sigmoid as convolution layer;
- the pooling layer takes a down sampling strategy on feeding forward, which means data was zipped;
- dnn applies matrix multiplication towards each layer directly, while cnn applies sum up of convolutional operation to each layer;
- and in a word, it’s vector, participated in dnn operation, and it’s tensor, participated in cnn operation.

We need to solve these differentiations to solve back propagation in cnn.

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