Code injecting/assembly inlining in Java?

Question

I know Java is a secure language but when matrix calculations are needed, can I try something faster?

I am learning __asm{} in C++, Digital-Mars compiler and FASM. I wan

Answer 1

There is a layer of abstraction between your Java code and the underlying hardware that makes this kind of thing impossible in principle; you technically can't know how your code is represented on the underlying machine, since the same bytecode can run on different processors and different architectures.

What you officially can do is use the Java Native Interface (JNI) to call native code from your Java code. The call overhead is substantial, and sharing data with Java is fairly expensive, so this should be used only for decent-sized chunks of native code.

In theory, such an extension should be possible, though. One can imagine a Java compiler that targeted a specific platform and allowed assembly escapes. The compiler would have to publish its ABI, so you'd know the calling conventions. I'm not aware of any that do, however. But there are several compilers available that compile Java directly to native code; it's possible one of them supports something like this without my knowing, or could be extended to do so.

Finally, on a different level altogether, there are bytecode assemblers for the JVM, like Jasmin. A bytecode assembler lets you write "machine code" that targets the JVM directly, and sometimes you can write better code than the javac compiler can generate. It's fun to play with, in any event.