University:
California State University, Northridge
Course:
COMP 333 | Concepts of Programming Languages
Academic year:

2023
Views:

323

Pages:

2
Author:

Samuel K

NYI NYI MOE HTET COMP 333 ASSIGNMENT 6 1. Busy waiting is a method whereby a task waits for a given event by continuously checking for that event to occur. What is the main problem with this approach? This approach is inefficient because it is wasting CPU cycles while repeatedly checking for the event to occur. If the task were suspended until the event occurred, those cycles could be used by another task. 2. Suppose two tasks, A and B, must use the shared variable Buf_Size. Task A adds 2 to Buf_Size, and task B subtracts 1 from it. Assume that such arithmetic operations are done by the three-step process of fetching the current value, performing the arithmetic, and putting the new value back. In the absence of competition synchronization, what sequences of events are possible and what values result from these operations? Assume that the initial value of Buf_Size is 6. If A runs to completion, then B runs to completion, Buf_Size has the value 7 (6 + 2 - 1). If B runs to completion, then A runs to completion, Buf_Size has the value 7 (6 – 1 + 2). If A runs but is interrupted after it fetches Buf_Size but before it stores the modified value (allowing B to fetch Buf_Size), or if B runs first and is interrupted after the fetch but before the store, allowing A to fetch Buf_Size, then if A finishes last Buf_Size will have value 8, and if B finishes last Buf_Size will have value 5. 3. Compare the Java cooperation synchronization mechanism with that of Ada. Java uses "wait/notify" tools built into every object except the root "Object" class itself. These tools let threads tell each other when to pause and resume, fine-tuning their cooperation. Ada takes a different approach where two tasks can meet in a "rendezvous" where one waits until the other finishes, offering simpler control but less flexibility. 4. What happens if a monitor procedure calls another procedure in the same monitor? Since the monitor's access mechanisms are built-in, it can enforce synchronized access by allowing only one operation at a time. Calls to its procedures are automatically queued and blocked if the monitor is busy, ensuring each operation gets its turn without interference. 5. Explain the relative safety of cooperation synchronization using semaphores and using Ada’s when clauses in tasks. Semaphores require explicit management of entry and exit points, and improper usage can lead to potential deadlocks or race conditions. On the other hand, Ada's when clauses offer a higher level of safety by allowing tasks to synchronize based on specific conditions without explicit locking mechanisms. Ada's built-in support for task synchronization through selective waiting with when clauses, reduces the risk of common synchronization issues, promoting cleaner and more reliable concurrent programming practices in comparison to manual semaphore management.