A multi processor system with 16 processors is used to execute a…
2024
A multi processor system with 16 processors is used to execute a parallelizable task. If the serial portion of the task takes 200 clock cycles and the parallel portion take 800 clock cycles. When all 16 processor are used how many total clock cycles are required to complete the task?
- A.
250
- B.
300
- C.
400
- D.
450
Attempted by 118 students.
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Correct answer: A
Key idea: the serial portion must be executed by a single processor and does not benefit from parallelism; the parallel portion is split evenly among all processors.
Compute the parallel time per processor: 800 ÷ 16 = 50 cycles.
Add the serial portion: total time = 200 + 50 = 250 cycles.
Final answer: 250 clock cycles when using all 16 processors.
Common mistake: dividing the parallel portion by the wrong number of processors (for example 8 or 4) leads to answers like 300 or 400; always divide the parallel portion by the actual number of processors available.
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