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

Coordinated transactional ref and state


We saw in an earlier section that an atom provides an atomic read-and-update operation. What if we need to perform an atomic read-and-update operation across two or even more atoms? This clearly poses a coordination problem. Some entity has to be watching over the process of reading and updating so that the values are not corrupted. This is what a ref provides—a system based on software transactional memory (STM). This takes care of concurrent atomic read-and-update operations across multiple refs such that either all updates go through or, in the case of failure, none do. Like atoms, on failure, refs retry the whole operation from scratch with new values.

Clojure's STM implementation is coarse grained—it works on the application level's objects and aggregates (references to aggregates), which are scoped to just all the refs in a program constituting Ref world. Any update to a ref can only happen synchronously in a transaction in a dosync block of code...