Running Scala on GraalVM
GraalVM is a JVM, so you can run Java and Scala programs normally using the
export GRAALVM_HOME=<path to GraalVM>/Content/Home export PATH=$GRAALVM_HOME/bin:$PATH $GRAALVM_HOME/bin/java -version java version "1.8.0_261" Java(TM) SE Runtime Environment (build 1.8.0_261-b33) Java HotSpot(TM) 64-Bit Server VM GraalVM EE 20.2.0 (build 25.261-b33-jvmci-20.2-b03, mixed mode)
If you are using sbt as the build tool, you can specify
JAVA_HOME it will use from the command line:
sbt -java-home $GRAALVM_HOME
GraalVM performs really well on the Scala benchmarks, for example you can look at Renaissance benchmarks suite. Note that Scala compiler is a Scala application as well, and it benefits from GraalVM runtime and runs faster too.
Native Image of Scala Compiler #
In this guide, you will learn how to get started with running Scala programs on
top of GraalVM and build a native image of
scalac – the Scala compiler.
GRAALVM_HOMEenvironment variables resolve to Scala 2.12.x and GraalVM respectively on macOS:
export GRAALVM_HOME=<path to GraalVM>/Content/Home export SCALA_HOME=/usr/local/opt/scala
and on Linux platforms:
export GRAALVM_HOME=<path to GraalVM> export SCALA_HOME=/usr/local/share
- Clone or download the repository and navigate to the scalac-native directory:
git clone https://github.com/graalvm/graalvm-demos cd graalvm-demos/scala-days-2018/scalac-native
- Build the
sbtproject from the scalac-substitutions directory:
cd scalac-substitutions sbt package cd ../
- Build the native image of the Scala compiler by running:
scalac-native.shcalls the generated compiler and passes all the required parameters. If you check the directory, the produced native image, called
scalac, with no dependencies on the JDK, should have appeared.
- Compare the execution time to the JVM:
$ time $SCALA_HOME/bin/scalac HelloWorld.scala real 0m2.315s user 0m5.868s sys 0m0.248s & time ./scalac-native HelloWorld.scala real 0m0.177s user 0m0.129s sys 0m0.034s
When the Scala compiler is ahead-of-time compiled with the profile-guided
optimization (PGO) enabled, the native
scalac is as fast as the one running on
the JVM (the C2 compiler).
Important: Profile-guided optimizations are available with GraalVM Enterprise Edition.
Support for Scala Macros #
To support macros – functions that are called by the compiler during compilation – the macro classes must be known to the native image builder of the Scala compiler. To build a scalac native image that includes macros run:
./scalac-native macros/GreetingMacros.scala -d macros/ ./scalac-image-macros.sh
Now you can compile a project that uses macros from
./scalac-native -cp macros/ HelloMacros.scala
Run the compiled program with:
$ scala HelloMacros Hello, World!