Introduction
After AlexNet, the obvious question was: how do we go deeper? In 2014, two teams gave very different answers.
- VGG (Oxford's Visual Geometry Group) said: keep it simple. Use only tiny 3 × 3 filters and stack lots of them.
- GoogLeNet (Google) said: be clever. Build a special module that looks at the image with several filter sizes at once, and use 1 × 1 convolutions to keep the cost down.
Think of two ways to build a tall tower. VGG stacks identical, simple bricks very high. GoogLeNet designs a clever, lightweight prefabricated unit and stacks those. Both towers ended up much taller (deeper) than AlexNet, and both ideas are still used today.