What is the Difference Between Interpreter and JIT Compiler

The main difference between Interpreter and JIT compiler is that the interpreter is a software that converts the source code into native machine code line by line while JIT compiler is a component in JVM that improves the performance of Java programs by compiling bytecodes into native machine codes at runtime.

Interpreter is a program that translates the programmer written instructions or scripts into corresponding machine code that matches a particular hardware platform of a CPU. On the other hand, JIT is a compiler that translates bytecodes into machine codes at runtime. It requires CPU time and memory.

Key Areas Covered

1. What is Interpreter
     – Definition, Functionality
2. What is JIT Compiler
     – Definition, Functionality
3. What is the Difference Between Interpreter and JIT Compiler
     – Comparison of Key Differences

Key Terms

Bytecode, Interpreter, JIT Compiler, JVM, Machine Code

What is Interpreter

Programmers write computer programs using a high-level programming language. He can easily read and understand the syntax of these programs. However, the CPU does not understand these programs to execute the task defined in the program. Therefore, it is necessary to convert the high-level source code into machine understandable machine code.

Figure 1: Python Interpreter

Interpreter is a software that performs the above-mentioned conversion. It converts the source code of the program to machine code line by line. As it checks one line at a time, the scanning time is lower. But the overall execution time of the program is higher. Therefore, the interpreter-based languages such as Python, Perl, Ruby, and, PHP are slower languages.

What is JIT Compiler

The javac compiler converts the Java source code into a bytecode. The Java Virtual Machine (JVM) can execute this bytecode. It converts that bytecode in the equivalent machine code so that the CPU can execute the task defined in the program. JIT stands for Just in Time compiler. It is an integral component of JVM. Moreover, it supports the JVM to execute Java bytecode faster and improves the performance of Java programs.

Figure 2: Java Bytecode

Any computer that has JVM installed to it can execute the bytecode.  In other words, any platform with JVM can install the bytecode. This makes Java platform-independent programming language.

Difference Between Interpreter and JIT Compiler

Definition

Interpreter is a software that converts the instructions written in a high-level programming or scripting language into machine language program. JIT compiler is a component of the Java Runtime Environment (JVM is a part of JRE) that improves the performance of Java applications at runtime. These definitions explain the main difference between Interpreter and JIT compiler.

Functionality

Interpreter converts the source code line by line into machine code. JIT compiler helps to execute bytecode faster by compiling the bytecode to machine code at runtime.

Execution speed

The execution speed of an interpreter is slower than a JIT compiler. This is also a difference between Interpreter and JIT compiler.

Associated Languages

Another difference between Interpreter and JIT compiler is that PHP, Perl, Python, Ruby are some interpreter based languages while Java uses JIT compiler.

Conclusion

The basic difference between Interpreter and JIT compiler is that interpreter is a software that converts the source code into native machine code line by line while JIT compiler is a component in JVM that improves the performance of Java programs by compiling bytecodes into native machine codes at run time.

Reference:

1. “Interpreter (Computing).” Wikipedia, Wikimedia Foundation, 28 Sept. 2018, Available here.
2. “JIT compiler overview”, IBM Knowledge Center, Available here.
3. Aboullaite, Mohammed. “Understanding JIT Compiler (Just-in-Time Compiler).” Aboullaite Med, 31 Aug. 2017, Available here.

Image Courtesy:

1. “Windows 7 Python Shell Interpreter prompt 11 May 2016” By Annakoppad – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Java-program-execution” By Loboh – Own work (CC BY-SA 3.0) via Commons Wikimedia