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

Performance and queuing theory


If we observe the performance benchmark numbers across a number of runs, even though the hardware, load, OS, and so on remain the same, the numbers are rarely exactly the same. The difference between each run may be upto as much as ±8 percent for no apparent reason. This may seem surprising, but the deep-rooted reason is that the performances of computer systems are stochastic by nature. There are many small factors in a computer system that make performance unpredictable at any given point of time. At best, the performance variations can be explained by a series of probabilities over random variables.

The basic premise is that each subsystem is more or less like a queue where requests await their turn to be served. The CPU has an instruction queue with unpredictable fetch/decode/branch-predict timings; the memory access again depends on the cache hit ratio and whether it needs to be dispatched via the interconnect, I/O subsystem works using interrupts that...