JIT vs. Interpreter
The Just In Time compilation (also known as dynamic translation or JIT) is a technique used in computing to improve the quality of the runtime performance of a computer program. It is the amalgamation of two ideas found in runtime environments: Bytecode compilation and dynamic compilation (which is a process that some programming language implementations use in order to gain performance while a system is executing an action).
An interpreter most accurately describes the execution of an action through a computer program. There are a few variations on the type of actions an interpreter actually executes: It directly executes the source code of a program; it translates the source code into a representation that is an efficient intermediate representation, and then executes the said code; it executes precompiled code that has been stored and created by a compiler that is part of the interpreter system.
JIT has the capability to combine the advantages found both in interpretation and static (that is to say ahead of time) compilation. As an interpreter, JIT is able to improve performance through caching results of blocks of code that has been translated – compared to simply re-evaluating every line or operand in the code each time that it occurs (as in interpreted language). Just like static compiling code at the time of development, JIT is able to recompile the code if this is found to be the most advantageous plan of action. Also, in the same vein as static compilation, JIT is capable of enforcing security guarantees.
Just like compilers, interpreters have the capacity to translate code. Both are the primary methods of implementing programming languages; however, the categories of ‘compiler’ or ‘interpreter’ are not distinct (for their dual roles as code translators). The most obvious disadvantage to using an interpreter is that once the code is interpreted, the program will inevitably run slower than when simply compiling the code; however, it takes much less time to interpret coding than it does to compile and run it (especially pertinent when prototyping and testing code).
Generally speaking, JIT provides much better performance than interpreters, and, in many cases, provides much better performance than static compilers. Its superiority over JIT, however, does not bar it from having some major disadvantages: There is a slight delay when initially executing an application (a side effect of taking time to load and compile bytecode). It will eventually generate better coding; however, the initial delay inherent in doing so will increase with the quality of coding.
Summary:
1. JIT is a technique used to improve the quality of performance of runtime in a runtime environment; an interpreter defines the execution of an action through a computer program.
2. JIT combines the advantages of interpretation and static compilation; an interpreter can translate code just like a compiler, but to the detriment of the speed of the program.