Book Image

Clojure High Performance Programming

By : Shantanu Kumar
Book Image

Clojure High Performance Programming

By: Shantanu Kumar

Overview of this book

<p>Clojure is a young, dynamic, functional programming language that runs on the Java Virtual Machine. It is built with performance, pragmatism, and simplicity in mind. Like most general purpose languages, Clojure’s features have different performance characteristics that one should know in order to write high performance code.<br /><br />Clojure High Performance Programming is a practical, to-the-point guide that shows you how to evaluate the performance implications of different Clojure abstractions, learn about their underpinnings, and apply the right approach for optimum performance in real-world programs.<br /><br />This book discusses the Clojure language in the light of performance factors that you can exploit in your own code.</p> <p>You will also learn about hardware and JVM internals that also impact Clojure’s performance. Key features include performance vocabulary, performance analysis, optimization techniques, and how to apply these to your programs. You will also find detailed information on Clojure's concurrency, state-management, and parallelization primitives.</p> <p>This book is your key to writing high performance Clojure code using the right abstraction, in the right place, using the right technique.</p>
Table of Contents (15 chapters)
Clojure High Performance Programming
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Asynchronous agents and state


While atoms are synchronous, agents are the asynchronous mechanism in Clojure that affect any change in state. Every agent is associated with a mutable state. We pass a function (known as action) to an agent with optional additional arguments—this function gets queued for processing in another thread by the agent. All agents share two common thread pools: one for low-latency (potentially CPU-bound, cache-bound, or memory-bound) jobs and one for blocking (potentially I/O-related or lengthy processing) jobs. Clojure provides the send function for low-latency actions, send-off for blocking actions, and send-via to have the action executed on the user-specified thread pool instead of either of the preconfigured thread pools. All of send, send-off, and send-via return immediately. The following is how we can use them:

(def a (agent 0))
(send a inc)  ; invokes (inc 0) in another thread, sets a to result
@a  ; returns 1 (only if the `inc` action is done ; also see ...