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A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?
- a)-2
- b)-1
- c)1
- d)2
Correct answer is option 'D'. Can you explain this answer?
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Verified Answer
A shared variable x, initialized to zero, is operated on by four concu...
Processes can run in many ways, below is one of the cases in which x attains max value
Semaphore S is initialized to 2
Process W executes S=1, x=1 but it doesn't update the x variable.
Then process Y executes S=0, it decrements x, now x= -2 and signal semaphore S=1
Now process Z executes s=0, x=-4, signal semaphore S=1
Now process W updates x=1, S=2 Then process X executes X=2
So correct option is D
Now process W updates x=1, S=2 Then process X executes X=2
So correct option is D
Most Upvoted Answer
A shared variable x, initialized to zero, is operated on by four concu...
Explanation:
Let's analyze the given scenario step by step to determine the maximum possible value of x after all processes complete execution.
Step 1: Initialization
- The shared variable x is initialized to zero.
- Semaphore S is initialized to two.
Step 2: Processes W and X
- Both process W and process X read the value of x from memory. At this point, x is still zero.
- Each process increments the value of x by one.
- Both processes store the updated value of x to memory.
- Before storing x to memory, both processes invoke the P operation on semaphore S, which decreases the value of S by one. Since S was initialized to two, its value becomes one after both processes complete the P operation.
- After storing x to memory, both processes invoke the V operation on semaphore S, which increases the value of S by one. As a result, the value of S becomes two again.
Step 3: Processes Y and Z
- Both process Y and process Z read the value of x from memory. At this point, x is incremented by two (due to the operations performed by process W and process X).
- Each process decrements the value of x by two.
- Both processes store the updated value of x to memory.
- Before storing x to memory, both processes invoke the P operation on semaphore S, which decreases the value of S by one. Since S was already two, its value becomes one after both processes complete the P operation.
- After storing x to memory, both processes invoke the V operation on semaphore S, which increases the value of S by one. As a result, the value of S becomes two again.
Step 4: Final value of x
- After all processes have completed execution, the final value of x can be calculated as follows:
- The initial value of x is zero.
- Processes W and X increment x by one each, resulting in an increase of two.
- Processes Y and Z decrement x by two each, resulting in a decrease of four.
- Therefore, the maximum possible value of x after all processes complete execution is 2 (initial value of x + increase of two - decrease of four).
Hence, the correct answer is option 'D' - 2.
Let's analyze the given scenario step by step to determine the maximum possible value of x after all processes complete execution.
Step 1: Initialization
- The shared variable x is initialized to zero.
- Semaphore S is initialized to two.
Step 2: Processes W and X
- Both process W and process X read the value of x from memory. At this point, x is still zero.
- Each process increments the value of x by one.
- Both processes store the updated value of x to memory.
- Before storing x to memory, both processes invoke the P operation on semaphore S, which decreases the value of S by one. Since S was initialized to two, its value becomes one after both processes complete the P operation.
- After storing x to memory, both processes invoke the V operation on semaphore S, which increases the value of S by one. As a result, the value of S becomes two again.
Step 3: Processes Y and Z
- Both process Y and process Z read the value of x from memory. At this point, x is incremented by two (due to the operations performed by process W and process X).
- Each process decrements the value of x by two.
- Both processes store the updated value of x to memory.
- Before storing x to memory, both processes invoke the P operation on semaphore S, which decreases the value of S by one. Since S was already two, its value becomes one after both processes complete the P operation.
- After storing x to memory, both processes invoke the V operation on semaphore S, which increases the value of S by one. As a result, the value of S becomes two again.
Step 4: Final value of x
- After all processes have completed execution, the final value of x can be calculated as follows:
- The initial value of x is zero.
- Processes W and X increment x by one each, resulting in an increase of two.
- Processes Y and Z decrement x by two each, resulting in a decrease of four.
- Therefore, the maximum possible value of x after all processes complete execution is 2 (initial value of x + increase of two - decrease of four).
Hence, the correct answer is option 'D' - 2.
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A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer?
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A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer?.
A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer?.
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A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer?, a detailed solution for A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? has been provided alongside types of A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?a)-2b)-1c)1d)2Correct answer is option 'D'. Can you explain this answer? theory, EduRev gives you an
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