Book Image

Haskell High Performance Programming

By : Samuli Thomasson
Book Image

Haskell High Performance Programming

By: Samuli Thomasson

Overview of this book

Haskell, with its power to optimize the code and its high performance, is a natural candidate for high performance programming. It is especially well suited to stacking abstractions high with a relatively low performance cost. This book addresses the challenges of writing efficient code with lazy evaluation and techniques often used to optimize the performance of Haskell programs. We open with an in-depth look at the evaluation of Haskell expressions and discuss optimization and benchmarking. You will learn to use parallelism and we'll explore the concept of streaming. We’ll demonstrate the benefits of running multithreaded and concurrent applications. Next we’ll guide you through various profiling tools that will help you identify performance issues in your program. We’ll end our journey by looking at GPGPU, Cloud and Functional Reactive Programming in Haskell. At the very end there is a catalogue of robust library recommendations with code samples. By the end of the book, you will be able to boost the performance of any app and prepare it to stand up to real-world punishment.
Table of Contents (21 chapters)
Haskell High Performance Programming
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Software Transactional Memory


Software Transactional Memory (STM) is the highest-level general concurrency abstraction we will consider. STM provides composable atomic transactions, meaning we can combine reads, writes, and other operations in multiple memory locations into single atomic operations. Transactions can be aborted or retried.

An STM transaction lives in the STM monad:

data STM a
instance Monad STM

Transactions are performed with the atomically function:

atomically :: STM a → IO a

Another important primitive is the retry function, which aborts the current transaction and retries it when some of its dependencies have changed (in some other transaction in another thread):

retry :: STM a

Basic transactional variables are provided by the STM package itself. Advanced structures are provided by additional packages. The following are provided in stm:Control.Concurrent.STM:

  • TVar: A shared memory location analogous to IORef, but transactional

  • TMVar: Mutable variable analogous to IORef

  • TChan: Channels...