MCQs on Performance Optimization | Ruby

Optimizing Ruby code is essential for better performance. This chapter covers profiling tools, garbage collection, memory management, and techniques to enhance Ruby program efficiency. The MCQs below will help assess your understanding.

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1. Profiling Ruby Code (Benchmark, memory_profiler)

1. Which Ruby gem is commonly used to measure the execution time of code?
   • A) memory_profiler
   • B) benchmark
   • C) ruby-prof
   • D) stackprof
2. How can you measure memory usage in Ruby code?
   • A) Using the benchmark gem
   • B) Using the memory_profiler gem
   • C) Using ObjectSpace
   • D) Using the gc module
3. What does the Benchmark.measure method return?
   • A) The memory usage of a block of code
   • B) The time taken to execute the block of code
   • C) The number of objects created in the block
   • D) The garbage collection statistics
4. Which of the following is NOT a valid method in the Benchmark module in Ruby?
   • A) Benchmark.realtime
   • B) Benchmark.measure
   • C) Benchmark.time
   • D) Benchmark.bmbm
5. What is the primary use of the memory_profiler gem in Ruby?
   • A) To find memory leaks in Ruby programs
   • B) To profile CPU usage
   • C) To optimize method execution time
   • D) To generate garbage collection reports

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2. Garbage Collection and Memory Management

6. In Ruby, what does garbage collection do?
   • A) It optimizes CPU usage
   • B) It frees up memory by removing unreachable objects
   • C) It caches memory for faster access
   • D) It compresses memory to save space
7. Which method is used to manually trigger garbage collection in Ruby?
   • A) ObjectSpace.garbage_collect
   • B) GC.start
   • C) GC.collect
   • D) ObjectSpace.cleanup
8. How can you check the current memory usage of your Ruby application?
   • A) Using the ObjectSpace module
   • B) Using the GC module
   • C) Using MemoryStats gem
   • D) Using the memory_profiler gem
9. What does the GC.stat method return in Ruby?
   • A) The current memory usage
   • B) The garbage collection statistics
   • C) The total time taken by garbage collection
   • D) The memory freed by the garbage collector
10. Which garbage collection strategy does Ruby use for automatic memory management?
    • A) Reference Counting
    • B) Mark and Sweep
    • C) Tracing Garbage Collection
    • D) Generational Garbage Collection

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3. Optimizing Ruby Code

11. What is the main goal of code optimization in Ruby?
    • A) To reduce memory usage
    • B) To improve execution speed and efficiency
    • C) To increase the number of features
    • D) To make the code more readable
12. Which of the following is a way to optimize memory usage in Ruby?
    • A) Use more memory-intensive data structures
    • B) Avoid object creation in loops
    • C) Use eval to execute code dynamically
    • D) Use unnecessary nested loops
13. How can you improve performance when working with large datasets in Ruby?
    • A) Use more memory-heavy data structures
    • B) Use lazy enumerators to process data on demand
    • C) Avoid using indexes
    • D) Avoid loops entirely
14. Which of the following can improve Ruby performance when accessing large arrays?
    • A) Use Array#each instead of each_with_index
    • B) Use Array#map instead of each
    • C) Avoid arrays and use hashes
    • D) Avoid using loops for array manipulation
15. How can you avoid memory leaks in Ruby?
    • A) Always free memory manually
    • B) Avoid using blocks
    • C) Avoid creating too many objects
    • D) Use proper object references and rely on garbage collection

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4. Profiling and Analyzing Performance Bottlenecks

16. Which Ruby tool can be used to generate a detailed report on memory usage and object allocations?
    • A) memory_profiler
    • B) ruby-prof
    • C) stackprof
    • D) Benchmark
17. How can you find the memory consumption of a specific object in Ruby?
    • A) Using ObjectSpace.memsize_of
    • B) Using GC.stat
    • C) Using ObjectSpace.memory_size
    • D) Using MemoryStats gem
18. What is the ruby-prof gem used for in Ruby?
    • A) To profile the memory usage of objects
    • B) To measure the execution time of Ruby code
    • C) To generate detailed performance profiles for method calls
    • D) To profile database queries
19. How can you identify performance bottlenecks in your Ruby code?
    • A) By using Benchmark.measure
    • B) By using memory_profiler
    • C) By running your code through ruby-prof
    • D) All of the above
20. What does the ruby-prof gem provide that is useful for optimization?
    • A) Graphical representations of memory usage
    • B) Detailed method call statistics and execution time
    • C) A summary of code errors
    • D) A way to track variable assignments

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5. Advanced Optimization Techniques

21. Which of the following methods can help reduce method call overhead in Ruby?
    • A) Use Symbol instead of String
    • B) Use Array#map instead of loops
    • C) Use def instead of lambda
    • D) Use caching and memoization for frequent method calls
22. Which technique is recommended for improving performance in Ruby when handling multiple method calls in a loop?
    • A) Use eval
    • B) Use method aliasing
    • C) Use memoization to store results of expensive computations
    • D) Use global variables instead of local variables
23. In Ruby, what is the effect of using #freeze on an object?
    • A) It makes the object immutable, preventing modifications
    • B) It improves memory performance by preventing garbage collection
    • C) It increases the object’s allocation size
    • D) It speeds up method execution
24. What can be a negative side effect of excessive use of the #dup method in Ruby?
    • A) Increased memory usage
    • B) Reduced method call performance
    • C) Reduced garbage collection frequency
    • D) Increased object immutability
25. How does memoization help in optimizing Ruby code performance?
    • A) By reducing memory usage
    • B) By preventing unnecessary method re-evaluations
    • C) By speeding up method calls using caching
    • D) By optimizing object creation

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6. Garbage Collection and Optimization

26. What is the purpose of using GC.compact in Ruby?
    • A) To reduce the memory usage of the application
    • B) To manually trigger garbage collection
    • C) To optimize memory after garbage collection
    • D) To collect unused variables
27. What does the ObjectSpace.each_object method allow you to do in Ruby?
    • A) Get the current status of garbage collection
    • B) Iterate through all objects in memory
    • C) Get memory statistics
    • D) Collect objects for garbage collection
28. Which Ruby command is useful for debugging memory issues in an application?
    • A) ruby-prof
    • B) ObjectSpace.each_object
    • C) memory_profiler
    • D) gc.garbage_collect
29. How does Ruby’s garbage collector identify objects for removal?
    • A) By analyzing object references and marking unreachable objects
    • B) By checking for variable assignment errors
    • C) By analyzing object creation times
    • D) By using reference counting
30. What is the effect of the GC::Profiler module in Ruby?
    • A) It tracks and provides garbage collection statistics
    • B) It reduces the frequency of garbage collection
    • C) It increases memory usage
    • D) It freezes objects during garbage collection

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Answer Table

Qno	Answer (Option with text)
1	B) benchmark
2	B) using the memory_profiler gem
3	B) The time taken to execute the block of code
4	C) Benchmark.time
5	A) To find memory leaks in Ruby programs
6	B) It frees up memory by removing unreachable objects
7	B) GC.start
8	D) Using the memory_profiler gem
9	B) The garbage collection statistics
10	D) Generational Garbage Collection
11	B) To improve execution speed and efficiency
12	B) Avoid object creation in loops
13	B) Use lazy enumerators to process data on demand
14	A) Use Array#each instead of each_with_index
15	D) Use proper object references and rely on garbage collection
16	A) memory_profiler
17	A) Using ObjectSpace.memsize_of
18	C) To generate detailed performance profiles for method calls
19	D) All of the above
20	B) Detailed method call statistics and execution time
21	D) Use caching and memoization for frequent method calls
22	C) Use memoization to store results of expensive computations
23	A) It makes the object immutable, preventing modifications
24	A) Increased memory usage
25	B) By preventing unnecessary method re-evaluations
26	C) To optimize memory after garbage collection
27	B) Iterate through all objects in memory
28	B) ObjectSpace.each_object
29	A) By analyzing object references and marking unreachable objects
30	A) It tracks and provides garbage collection statistics