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)

Implementing the Activation Function Layer

Now, we will apply the idea of a computational graph to a neural network. Here, we will implement the "layers" that constitute a neural network in one class using the ReLU and Sigmoid layers, which are activation functions.

ReLU Layer

A Rectified Linear Unit (ReLU) is used as an activation function and is expressed by the following equation (5.7):

49

(5.7)

From the preceding equation (5.7), you can obtain the derivative of y with respect to x with equation (5.8):

48

(5.8)

As equation (5.8) shows, if the input in forward propagation, x, is larger than 0, backward propagation passes the upstream value downstream without changing it. Meanwhile, if x is 0 or smaller in forward propagation, the signal stops there in backward propagation. You...