What does a JIT compiler do?

Question

I was just watching the Google IO videos and they talked about the JIT compiler that they included in the android. They showed a demo of performance improvements thanks to t

Answer 1

So, What is the duty of a JIT compiler?

As others mentioned it's short for "Just In Time", which in this sense means "Just in time for execution".

When you compile programs to machine code, they are often targeted to a certain platform.

Therefore JIT was "Invented", you want to compile the last bits and pieces of your code for the executing platform, so see this as an "before exection"-compiler/optimizer.

JIT makes our lives easier and makes (hopefully) our applications run faster.

There are of course other purposes of JIT-compilation, the above is just one of them.