## Summary

In this chapter, we looked at the most important concepts behind deep learning together with scalable solutions.

We took away some of the black-boxiness by learning how to construct the right architecture for any given task and worked through the mechanics of forward propagation and backpropagation. Updating the weights of a neural network is a hard task, regular stochastic gradient descent can result in getting stuck in global minima or overshooting. More sophisticated algorithms like momentum, ADAGRAD, RPROP and RMSProp can provide solutions. Even though neural networks are harder to train than other machine learning methods, they have the power of transforming feature representations and can learn any given function (universal approximation theorem). We also dived into large scale deep learning with H2O, and even utilized the very hot topic of parameter optimization for deep learning.

Unsupervised pre-training with auto-encoders can increase accuracy of any given deep network and...