JIT vs AOT compilation — what is the difference and advantages?

JIT (Just-In-Time) and AOT (Ahead-Of-Time) are two approaches to code compilation, differing in the timing and method of transforming source or intermediate code into machine code.

JIT compilation occurs during program execution. For example, the JVM initially loads bytecode and then compiles frequently used code sections into machine code on the fly. This allows optimizing the code based on the actual behavior of the program and the runtime environment.

Advantages of JIT:

• Profiling-based optimizations during execution.
• Ability to adapt to a specific platform and data.
• Fast startup, as compilation happens as needed.

AOT compilation occurs beforehand, before the program runs. The source or intermediate code is fully compiled into machine code, which is executed immediately.

Advantages of AOT:

• Fast application startup, as there is no compilation time during execution.
• Lower resource consumption during operation.
• Suitable for environments with limited resources or without JIT support.