# Capsule Network

# Capsule Network

## Paper

Dynamic Routing Between Capsules

### Ideas

The output of capsule is a vector, instead of a scaler. Vectors can carry more infomation, and each dimensions is interpretable.

The length of the vector represents the probablility.

- squash function: short vectors get shrunk to almost zero length, and long vectors get shrunk to a length slightly below 1.

High level features computed by routing algorithm, instead of using max-pooling, because max-pooling loses information.

**Routing algorithm**

- low layer vector times a parametric matrix to get next layer vector
- the relations between two layer vectors are weighted.
- similar to K-means to update the weight.
- backward to update the matrix.

### Implementation

## Paper

Matrix capsules with EM routing