Book Image

Deep Learning from the Basics

By : Koki Saitoh
5 (1)
Book Image

Deep Learning from the Basics

5 (1)
By: Koki Saitoh

Overview of this book

Deep learning is rapidly becoming the most preferred way of solving data problems. This is thanks, in part, to its huge variety of mathematical algorithms and their ability to find patterns that are otherwise invisible to us. Deep Learning from the Basics begins with a fast-paced introduction to deep learning with Python, its definition, characteristics, and applications. You’ll learn how to use the Python interpreter and the script files in your applications, and utilize NumPy and Matplotlib in your deep learning models. As you progress through the book, you’ll discover backpropagation—an efficient way to calculate the gradients of weight parameters—and study multilayer perceptrons and their limitations, before, finally, implementing a three-layer neural network and calculating multidimensional arrays. By the end of the book, you’ll have the knowledge to apply the relevant technologies in deep learning.
Table of Contents (11 chapters)

Backward Propagation

The previous section described how backward propagation in a computational graph is based on the chain rule. We will now cover how backward propagation works by taking operations, such as "+" and "x", as examples.

Backward Propagation in an Addition Node

First, let's consider backward propagation in an additional node. Here, we will look at backward propagation for the equation z = x + y. We can obtain the derivatives of z = x + y (analytically) as follows:

13

(5.5)

As equation (5.5) shows, both 15 and 16 are 1. Therefore, we can represent them in a computational graph, as shown in the following diagram. In backward propagation, the derivative from the upper stream—17, in this example—is multiplied by 1 and passed downstream. In short, backward propagation in an addition node multiplies 1, so it only passes the input value to the...