Book Image

Clojure Data Analysis Cookbook

By : Eric Rochester
Book Image

Clojure Data Analysis Cookbook

By: Eric Rochester

Overview of this book

<p>Data is everywhere and it's increasingly important to be able to gain insights that we can act on. Using Clojure for data analysis and collection, this book will show you how to gain fresh insights and perspectives from your data with an essential collection of practical, structured recipes.<br /><br />"The Clojure Data Analysis Cookbook" presents recipes for every stage of the data analysis process. Whether scraping data off a web page, performing data mining, or creating graphs for the web, this book has something for the task at hand.<br /><br />You'll learn how to acquire data, clean it up, and transform it into useful graphs which can then be analyzed and published to the Internet. Coverage includes advanced topics like processing data concurrently, applying powerful statistical techniques like Bayesian modelling, and even data mining algorithms such as K-means clustering, neural networks, and association rules.</p>
Table of Contents (18 chapters)
Clojure Data Analysis Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Parallelizing processing with pmap


The easiest way to parallelize data is to take a loop we already have and handle each item in it in a thread.

That is essentially what pmap does. If we replace a call to map with pmap, it takes each call to the function argument and executes it in a thread pool. pmap is not completely lazy, but it's not completely strict, either: it stays just ahead of the output consumed. So if the output is never used, it won't be fully realized.

For this recipe, we'll calculate the Mandelbrot set. Each point in the output takes enough time that this is a good candidate to parallelize. We can just swap map for pmap and immediately see a speed-up.

How to do it…

The Mandelbrot set can be found by looking for points that don't settle on a value after passing through the formula that defines the set quickly.

  1. We need a function that takes a point and the maximum number of iterations to try and return the iteration that it escapes on. That just means that the value gets above 4...