Scalaxy/Loops

Optimized Range foreach loops for Scala (using a macro to rewrite them to an equivalent while loop). (BSD-licensed)

Works with Scala 2.10.x and Scala 2.11.x, but 2.11.x users are kindly advised to migrate to Scalaxy/Streams.

Caveats:

• Experimental material: use at your own risk (and avoid using in your tests :-D).
• The Scala 2.10.x variant has some ad-hoc Range foreach loop optimization code.
• The Scala 2.11.x variant leverages Scalaxy/Streams in a non-recursive mode (which means only the stream in which the optimized range loop is involved is optimized). To get the full power of Scalaxy/Streams, please use it directly (this version is here to allow cross-compilation of 2.10.x code written with Scalaxy/Loops).

The following expression:

import scalaxy.loops._
import scala.language.postfixOps // Optional.

for (i <- 0 until 100000000 optimized) {
  ...
}

Will get rewritten at compilation time into something like:

{
  var ii = 0
  val end = 100000000
  val step = 1
  while (ii < end) {
    val i = ii
    ...
    ii += step
  }
}

This is a rejuvenation of some code initially written for ScalaCL then for optimized-loops-macros.

(see this blog post for a recap on the ScalaCL project rationale / story)

Usage with Sbt

If you're using sbt 0.13.0+, just put the following lines in build.sbt:

scalaVersion := "2.11.6"
// Or:
// scalaVersion := "2.10.4"

// Dependency at compilation-time only (not at runtime).
libraryDependencies += "com.nativelibs4java" %% "scalaxy-loops" % "0.3.3" % "provided"

// If you care about speed, you may want to enable these:
// scalacOptions ++= Seq("-optimise", "-Yclosure-elim", "-Yinline")

And append optimized to all the ranges you want to optimize:

for (i <- 0 until n optimized; j <- i until n optimized) {
  ...
}

If you like to live on the bleeding edge, try the latest snapshot out:

libraryDependencies += "com.nativelibs4java" %% "scalaxy-loops" % "0.4-SNAPSHOT" % "provided"

// Scalaxy snapshots are published on the Sonatype repository.
resolvers += Resolver.sonatypeRepo("snapshots")

You can always disable loop optimizations without removing the optimized postfix operator from your code: just recompile with the environment variable SCALAXY_LOOPS_OPTIMIZED=0 or the System property scalaxy.loops.optimized=false set:

SCALAXY_LOOPS_OPTIMIZED=0 sbt clean compile ...

Or if you're not using sbt:

scalac -J-Dscalaxy.loops.optimized=false ...

Usage with Maven

With Maven, you'll need this in your pom.xml file:

<dependencies>
  <dependency>
    <groupId>com.nativelibs4java</groupId>
    <artifactId>scalaxy-loops_2.11</artifactId>
    <!-- Or:
    <artifactId>scalaxy-loops_2.10</artifactId>
    -->
    <version>0.3.3</version>
  </dependency>
</dependencies>

If you like to live on the bleeding edge, try the latest snapshot out:

<dependencies>
  <dependency>
    <groupId>com.nativelibs4java</groupId>
    <artifactId>scalaxy-loops_2.11</artifactId>
    <!-- Or:
    <artifactId>scalaxy-loops_2.10</artifactId>
    -->
    <version>0.4-SNAPSHOT</version>
  </dependency>
</dependencies>

<repositories>
  <repository>
    <id>sonatype-oss-public</id>
    <url>https://oss.sonatype.org/content/groups/public/</url>
  </repository>
</repositories>

Hacking

If you want to build / test / hack on this project:

• Make sure to use paulp's sbt script with sbt 0.12.2+

• Use the following commands to checkout the sources and build the tests continuously:

  git clone git://github.com/ochafik/Scalaxy.git
  cd Scalaxy
  sbt "project scalaxy-loops" "; clean ; ~test"
  

  Or for the Scala 2.10.x version:

  cd Scalaxy
  sbt "project scalaxy-loops-210" "; +clean ; +test"
  

What's next?

No further optimizations will be specifically added to Scalaxy/Loops. Instead, work is now ongoing in Scalaxy/Streams, which Scalaxy/Loops delegates its optimizations to in its 2.11.x version.

Please file bugs and enhancement requests here.

Any help (testing, patches, bug reports) will be greatly appreciated!