Repa (REgular PArallel arrays) ¶

Repa provides high performance, regular, multi-dimensional, shape polymorphic parallel arrays. All numeric data is stored unboxed. Functions written with the Repa combinators are automatically parallel provided you supply +RTS -Nwhatever on the command line when running the program. Repa means "turnip" in Russian. If you don't like turnips then this library probably isn't for you.

Download ¶

Repa is split up into a few packages to help control dependencies.

​repa	The base library, defining the array type and combinators.
​repa-bytestring	Conversions to and from ByteString.
​repa-io	Reading and writing arrays in various formats, including BMP.
​repa-algorithms	Some reusable matrix algorithms.
​repa-devil	Bindings to the DevIL image library.
​repa-examples	Example applications.

If you want the lot then just install the examples, and this will pull down the rest.

cabal install repa-examples

From the source repo ¶

The darcs source repos are at ​http://code.ouroborus.net/repa/

Report a bug ¶

To report bugs, request features, or get an account on the trac, please send email to repa@ouroborus.net

Papers and Tutorials ¶

​Regular Shape Polymorphic Arrays in Haskell

• Describes the overall approach to fusion, and how the shape polymorphism works.
• Since this paper was published, the internals have changed slightly, but the overall structure is the same.

​Efficient Parallel Stencil Convolution in Haskell

• Describes the current array representation.
• Discusses the back-end, how the parallelism works, and how to write fast code.
• Describes Repa's special support for Stencil convolutions.

​Tutorial on usage and optimisation

• Contains lots of simple examples to get you started.
• High level discussion of fusion, optimisation, and how to use the force function.

Examples ¶

Here is the output of some of the examples included in the ​repa-examples package:

fft2d-highpass	Laplace
more info	more info

Demo ¶

There is also an OSX demo that does edge detection on a video stream:

video: ​low(10MB) ​high(40MB)

• The ​source should compile with XCode 3.2.1, GHC 7.0.3 and Repa 2.0.0, but you need to update and run the CONFIGURE.sh script to point it to your GHC install.
• There are also prebuilt OSX i386 versions for ​two ​four and ​six threads. These just have the corresponding +RTS -N# option baked in, you can set it in the main.m module. Some day I will make it so you can select this from the GUI.
• You can also run the edge detector over a single uncompressed .bmp file using the repa-canny program from the ​repa-examples package.