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

Non-numeric scalars and interning


Strings and characters in Clojure are the same as in Java. String literals are implicitly interned. Interning is a way of storing only unique values in the heap and sharing the reference wherever required. Depending on the provider and the version of Java you use, the interned data may be stored in a string pool, Permgen, ordinary heap, or some special area in the heap marked for interned data. Interned data is subject to garbage collection when not in use, just like ordinary objects. Take a look at the following code:

user=> (identical? "foo" "foo")  ; literals are automatically interned
true
user=> (identical? (String. "foo") (String. "foo"))  ; created string is not interned
false
user=> (identical? (.intern (String. "foo")) (.intern (String. "foo")))
true
user=> (identical? (str "f" "oo") (str "f" "oo"))  ; str creates string
false
user=> (identical? (str "foo") (str "foo"))  ; str does not create string for 1 arg
true
user=> (identical...