Book Image

Mastering Probabilistic Graphical Models with Python

By : Ankur Ankan
Book Image

Mastering Probabilistic Graphical Models with Python

By: Ankur Ankan

Overview of this book

Table of Contents (14 chapters)
Mastering Probabilistic Graphical Models Using Python
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Chapter 4. Approximate Inference

In the previous chapter, we saw algorithms for exact inference on graphical models. The computational complexity of calculating exact inference is exponential to the tree width of the network. Hence, for much larger networks whose tree width is large, exact inference becomes infeasible. Also, in many of our real-life problems, we are not particularly concerned about the exact probabilities of random variables. Rather, we are much more interested in the relative probabilities of the states of variables. Therefore, in this chapter, we will discuss algorithms to perform approximate inference over networks. There are many algorithms for approximate inference, but the approach to find an approximate distribution remains the same in all of them. In most of these, we usually define a target class Q of easy distributions, and then from this class, we try to find the distribution that is closest to our actual distribution and answer inference queries from this estimated...