MCQs on Advanced Concurrency and Parallelism | Haskell

Concurrency and parallelism are essential for achieving high performance in modern computing, especially when working with Haskell. This set of 30 multiple-choice questions (MCQs) covers advanced topics like Software Transactional Memory (STM), parallel Haskell using par and pseq, the Actor model, and distributed systems. These concepts are crucial for building efficient, scalable applications that can handle complex computations.

Topics:

Software Transactional Memory (STM)

1. Which of the following is the key feature of Software Transactional Memory (STM)? a) Lock-based synchronization
   b) Transactional consistency
   c) Multithreaded computation
   d) Data immutability
2. In Haskell’s STM, which type represents a transaction? a) MVar
   b) TVar
   c) IORef
   d) STRef
3. Which STM operation is used to start a new transaction in Haskell? a) atomically
   b) forkIO
   c) newTVarIO
   d) retry
4. In STM, the retry function causes the transaction to: a) Commit immediately
   b) Rollback and retry
   c) Exit the transaction
   d) Suspend the transaction
5. What is the default behavior of Haskell’s STM when a transaction cannot immediately complete? a) Immediate rollback
   b) Retry at a later time
   c) Block indefinitely
   d) Force a deadlock
6. Which of the following functions is used to commit a transaction in STM? a) commit
   b) atomic
   c) atomically
   d) commitSTM
7. How does STM in Haskell differ from traditional lock-based concurrency mechanisms? a) STM uses locks
   b) STM provides transactional guarantees without locks
   c) STM avoids multi-threading
   d) STM restricts the number of threads
8. What happens if two STM transactions attempt to modify the same TVar at the same time? a) Both transactions succeed
   b) One transaction succeeds, the other is aborted
   c) Both transactions block indefinitely
   d) A deadlock occurs
9. Which Haskell package provides the STM module for concurrency? a) Control.Concurrent
   b) Control.Monad
   c) Control.Concurrent.STM
   d) Control.Applicative
10. What is the primary advantage of STM over traditional locks in concurrent programming? a) Better performance
    b) Simpler code
    c) Avoidance of deadlock
    d) Easier debugging

Parallel Haskell and par/pseq for Parallel Computation

11. What is the purpose of par in Haskell? a) Sequential computation
    b) Parallelizing pure computations
    c) Managing stateful computations
    d) Handling IO operations
12. In Haskell, what is the function pseq used for? a) For parallel computation
    b) For sequential evaluation
    c) For creating threads
    d) For managing mutable variables
13. Which of the following is true about the relationship between par and pseq? a) par ensures order of execution
    b) pseq guarantees parallel execution
    c) par creates parallel threads, pseq enforces evaluation order
    d) par is for IO operations, pseq is for STM
14. What does the par combinator achieve in Haskell? a) It forces strict evaluation
    b) It signals that the computation can be performed in parallel
    c) It handles side-effects
    d) It suspends computation until needed
15. Which type of computation does pseq help with in a parallel setting? a) Lazy evaluation
    b) Strict evaluation
    c) Deadlock prevention
    d) IO operations
16. What is the result of using par without pseq in a parallel computation? a) A deadlock
    b) Undefined behavior
    c) Non-deterministic evaluation order
    d) Immediate computation
17. In which kind of computation is the combination of par and pseq most useful? a) Parallel recursive computation
    b) Sequential data transformation
    c) Single-threaded execution
    d) IO-bound tasks
18. How does parallel Haskell differ from traditional parallel programming models? a) Haskell does not support parallelism
    b) Haskell uses functional constructs for parallelism
    c) Haskell relies solely on multi-core processors
    d) Haskell only supports parallel loops
19. What does the Control.Parallel module provide in Haskell? a) Transactional memory support
    b) Parallel execution functions like par and pseq
    c) IO and mutable state
    d) Actor-based concurrency models
20. Which of the following describes the evaluation strategy for parallel Haskell code? a) Eager evaluation
    b) Lazy evaluation
    c) Strict evaluation
    d) Dynamic evaluation

Actors and Message-Passing Concurrency Models

21. Which of the following is a key concept in the Actor model of concurrency? a) Shared memory
    b) Message-passing between independent agents
    c) Locking mechanisms
    d) Centralized control
22. In the Actor model, each actor is responsible for: a) Sending and receiving messages
    b) Managing shared state
    c) Coordinating threads
    d) Synchronizing memory access
23. Which library provides actor-based concurrency in Haskell? a) Control.Concurrent
    b) ActorModel
    c) Control.Concurrent.Actor
    d) HAppS
24. What is the fundamental communication mechanism in the Actor model? a) Shared variables
    b) Direct function calls
    c) Message-passing
    d) Memory-mapped files
25. In the Actor model, what happens when an actor receives a message? a) It updates its own state and sends a response
    b) It immediately terminates
    c) It blocks all other actors
    d) It suspends other actors until completion
26. What does the Actor model avoid in comparison to traditional multi-threaded programming? a) Deadlock
    b) Race conditions
    c) Data-sharing between threads
    d) Thread synchronization
27. How do actors in the Actor model manage their state? a) Through mutable global variables
    b) Through message queues
    c) By synchronizing with other actors
    d) By having local private states
28. In Haskell, which function is typically used to send messages to an actor? a) sendMessage
    b) actorSend
    c) tell
    d) postMessage
29. Which of the following best describes the Actor model’s suitability for concurrent applications? a) Ideal for applications with shared memory
    b) Useful for applications with isolated processes communicating via messages
    c) Best suited for sequential computation
    d) Designed for applications with minimal communication between processes
30. What is a potential disadvantage of the Actor model in Haskell? a) Limited scalability
    b) High overhead in managing message queues
    c) Lack of support for parallel execution
    d) Complex state management

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