Just-in-Time Compilation MCQs

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1. What is the primary purpose of JIT compilation?
(A) To compile all code before execution
(B) To debug code automatically
(C) To interpret code without compilation
(D) To compile code at runtime for performance optimization

2. Which programming languages commonly use JIT compilation?
(A) C and C++
(B) Java and C#
(C) Assembly
(D) COBOL

3. What is the main advantage of JIT over traditional interpretation?
(A) Reduced memory usage
(B) Eliminates compilation entirely
(C) Improved runtime performance
(D) Simpler debugging

4. Which component is responsible for executing JIT-compiled code in Java?
(A) Java Runtime Environment (JRE)
(B) Java Virtual Machine (JVM)
(C) Java Development Kit (JDK)
(D) Java Compiler

5. What does adaptive optimization in JIT compilation refer to?
(A) Optimizing code dynamically based on runtime profiling
(B) Compiling only part of the code randomly
(C) Precompiling all possible code paths
(D) Ignoring hot spots in the code

6. Which of the following is a common type of JIT compilation?
(A) Both A and B
(B) Tracing JIT
(C) Method-based JIT
(D) Lexical JIT

7. What is a “hot spot” in the context of JIT compilation?
(A) A syntax error in the code
(B) Frequently executed code that benefits from optimization
(C) Memory leak location
(D) CPU-intensive operating system process

8. What is the main drawback of JIT compilation compared to ahead-of-time (AOT) compilation?
(A) Slower runtime for frequently executed code
(B) Cannot handle dynamic languages
(C) Reduced optimization opportunities
(D) Initial compilation overhead at runtime

9. What does tiered compilation in JIT mean?
(A) Using multiple levels of optimization based on code execution frequency
(B) Compiling code once and never optimizing
(C) Only interpreting code
(D) Compiling only non-critical code

10. Which type of JIT compiles entire methods at once?
(A) Method-based JIT
(B) Tracing JIT
(C) Interpreter-based JIT
(D) Ahead-of-Time JIT

11. How does tracing JIT work?
(A) Compiles code line by line sequentially
(B) Records frequently executed paths and compiles them into optimized machine code
(C) Interprets all code without optimization
(D) Generates bytecode for each function call

12. Which of the following is an example of a JIT-enabled runtime?
(A) JVM (Java Virtual Machine)
(B) NET CLR (Common Language Runtime)
(C) All of the above
(D) V8 JavaScript Engine

13. What is the role of a profiler in JIT compilation?
(A) Detects syntax errors
(B) Identifies hot spots to focus optimization efforts
(C) Allocates memory for variables
(D) Compiles the code before execution

14. Which optimization is commonly performed by JIT compilers?
(A) Constant folding
(B) Loop unrolling
(C) Inlining of frequently called functions
(D) All of the above

15. How does JIT compilation improve performance for dynamic languages like JavaScript?
(A) By compiling frequently executed code paths into machine code at runtime
(B) By interpreting code faster
(C) By reducing memory usage
(D) By removing all function calls

16. What is speculative optimization in JIT?
(A) Optimizing code without execution data
(B) Making assumptions about code behavior to generate faster code and deoptimizing if assumptions fail
(C) Ignoring hot spots
(D) Compiling unused code first

17. What is deoptimization in JIT compilation?
(A) Eliminating unnecessary code
(B) Increasing the code size
(C) Removing optimizations that fail at runtime to ensure correct program behavior
(D) Interpreting all code only

18. Which of the following is a benefit of method inlining in JIT?
(A) Reduces function call overhead
(B) Improves CPU cache utilization
(C) All of the above
(D) Enables further optimization opportunities

19. How does JIT handle dynamic type information?
(A) By ignoring types
(B) By using runtime type information to optimize code paths
(C) By converting all types to integers
(D) By static type checking only

20. What is code caching in JIT compilation?
(A) Storing source code only
(B) Deleting compiled code after execution
(C) Storing compiled machine code for reuse to avoid recompilation
(D) Compiling code only once per session

21. Which is a common challenge in JIT compilation?
(A) Balancing compilation time vs runtime performance
(B) All of the above
(C) Handling multi-threaded execution safely
(D) Memory management of compiled code

22. What does the term “warm-up period” mean in JIT?
(A) Initial execution phase where profiling data is collected before optimizations are applied
(B) Precompiling the entire program
(C) Cooling down the CPU
(D) None of the above

23. How does JIT impact startup time of programs?
(A) Decreases startup time
(B) Eliminates runtime execution entirely
(C) Has no impact
(D) Can increase startup time due to on-the-fly compilation

24. What is a common approach to mitigate JIT startup overhead?
(A) Ahead-of-Time (AOT) compilation
(B) All of the above
(C) Warm-up execution with profiling
(D) Lazy compilation of code only when needed

25. Which of the following is a widely used JavaScript JIT engine?
(A) SpiderMonkey
(B) V8
(C) All of the above
(D) Chakra

26. How does adaptive optimization differ from static optimization?
(A) Adaptive optimization reduces code size, static increases it
(B) Adaptive optimization occurs at runtime using profiling data, static optimization occurs at compile-time
(C) Static optimization is faster than adaptive
(D) There is no difference

27. Which of the following best describes tracing JIT?
(A) Compiles entire classes at once
(B) Converts source code directly to machine code without profiling
(C) Records frequently executed paths through loops and methods for optimization
(D) Only used in Java

28. What is the relationship between JIT and garbage collection in managed languages?
(A) JIT can optimize allocation and deallocation patterns for better garbage collection performance
(B) JIT compilation is independent of garbage collection
(C) JIT eliminates the need for garbage collection
(D) JIT slows down garbage collection only

29. What is the main reason for using tiered JIT compilation?
(A) Reduce memory usage
(B) Avoid dynamic profiling
(C) Simplify runtime
(D) Combine fast initial compilation with high-performance optimizations for hot code

30. Which statement best describes JIT compilation?
(A) It is a hybrid approach that compiles code at runtime for better performance
(B) It is static ahead-of-time compilation
(C) It is purely interpretation
(D) It only applies to low-level languages

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