Introduction to Artificial Neural Networks with Keras
Birds inspired us to fly, burdock plants inspired velcro, and countless more inventions were inspired by nature. It seems only logical, then, to look at the brain’s architecture for inspiration on how to build an intelligent machine. This is the key idea that sparked artificial neural networks (ANNs). However, although planes were inspired by birds, they don’t have to flap their wings. Similarly, ANNs have gradually become quite different from their biological cousins. Some researchers even argue that we should drop the biological analogy altogether (e.g., by saying “units” rather than “neurons”), lest we restrict our creativity to biologically plausible systems.ANNs are at the very core of Deep Learning. They are versatile, powerful, and scalable, making them ideal to tackle large and highly complex Machine Learning tasks, such as classifying billions of images (e.g., Google Images), powering speech recognition services (e.g., Apple’s Siri), recommending the best videos to watch to hundreds of millions of users every day (e.g., YouTube), or learning to beat the world champion at the game of Go by playing millions of games against itself (DeepMind’s Alpha‐ Zero).
In the first part of this tutorial, we will introduce artificial neural networks, starting with a quick tour of the very first ANN architectures, leading up to Multi-Layer Perceptrons (MLPs) which are heavily used today (other architectures will be explored in the next chapters). In the second part, we will look at how to implement neural networks using the popular Keras API. This is a beautifully designed and simple high level API for building, training, evaluating and running neural networks. But don’t be fooled by its simplicity: it is expressive and flexible enough to let you build a wide variety of neural network architectures. In fact, it will probably be sufficient for most of your use cases. Moreover, should you ever need extra flexibility, you can always write custom Keras components using its lower-level API,But first, let’s go back in time to see how artificial neural networks came to be!