How to use the Intel AVX in Java?

Question

How do I use the Intel AVX vector instruction set from Java? It's a simple question but the answer seems to be hard to find.

Answer 1

As I know, most current Java JVM JITters don't support automatic vectorization or just do that for very simple loops, so you're out of luck.

In Mono's .NET implementation there's Mono.Simd for manual vector code emission and then later MS introduced the System.Numeric.Vectors. Unfortunately there's nothing similar in Java. I don't know if Java's vector class is vectorized using SIMD or not but I don't think it is.

If you want to use CPU-specific features like AVX then your only choice is JNI. Write your bottle neck part in C or C++ and call it from Java

There's another solution by Scala to use vectorized code without modifying the JVM that you can read in How we made the JVM 40x faster

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Update:

Now there's a new Vector API being developed for writing vector code manually

Provide an initial iteration of an incubator module, jdk.incubator.vector, to express vector computations that reliably compile at runtime to optimal vector hardware instructions on supported CPU architectures and thus achieve superior performance to equivalent scalar computations.

https://openjdk.java.net/jeps/338

• Vector API Developer Program for Java* Software
• Oracle and Intel seek to build a Java API for SIMD support

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Read more:

• Do any JVM's JIT compilers generate code that uses vectorized floating point instructions?
• SIMD Vectors/Matrices in Java?
• What is the state of auto-vectorization in OpenJDK?
• Vectorized Algorithms in Java