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

Useful GHC extensions


We have already used a number of extensions available in GHC, such as MultiParamTypeClasses, TypeFamilies, FlexibleInstances, and so on. The nice thing about most extensions in GHC is that, if you accidentally try to use a language feature that is behind an extension, GHC gives you a hint about which extension you forgot.

In this last section, we'll look at some more useful extensions available in reasonably modern GHC. There are other extensions, of course, and this is just a glimpse. For an exhaustive list of currently supported extensions, see the Language.Haskell.Extension module from the Cabal library.

Monomorphism Restriction

Some of the most confusing type errors originate from the monomorphism restriction (MR). Consider this program:

-- file: mr.hs
main = do
    let f = (1 +)
    print $ f (6   :: Int)
    print $ f (0.1 :: Double)

The most general type for f would be Num a => a → a. But due to MR, the inferred type is monomorphic in a. The error message we...