java-simple-stream-benchmark.md

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Simple Java Stream Benchmark

This application is a small benchmark of the Java Stream API. It demonstrates how the GraalVM compiler can achieve better performance for highly abstracted programs like those using Streams, Lambdas, or other Java features.

Preparation

This example requires the Maven build tool.

1. Download or clone the repository and navigate into the java-simple-stream-benchmark directory:

git clone https://github.com/graalvm/graalvm-demos
cd graalvm-demos/java-simple-stream-benchmark

2. Build the benchmark. You can manually execute mvn package, but there is also a build.sh script included for your convenience:

./build.sh

3. Export the GraalVM home directory as the $GRAALVM_HOME and add $GRAALVM_HOME/bin to the path, using a command-line shell for Linux:

export GRAALVM_HOME=/path/to/graalvm

For macOS:

export GRAALVM_HOME=/path/to/graalvm/Contents/Home

Now you are all set to execute the benchmark and compare the results between different JVMs.

Running the Benchmark

To run the benchmark, you need to execute the target/benchmarks.jar file. You can run it with the following command:

java -jar target/benchmarks.jar

If you would like to run the benchmark on a different JVM, you can run it with whatever java you have. However, if you just want to run it on the same JVM, but without the GraalVM compiler, you may add the -XX:-UseJVMCICompiler option into the same command:

java -XX:-UseJVMCICompiler -jar target/benchmarks.jar

This way, the GraalVM compiler will not be used as the JVMCI compiler and the JVM will use its default one.

Note about Results

The benchmark mode is AverageTime in nanoseconds per operation, which means lower numbers are better. Note that the results you see can be influenced by the hardware you are running this benchmark on, the CPU load, and other factors. Interpret them responsibly.