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ISRO | ISRO CS 2013 | Question 61

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A particular parallel program computation requires 100 seconds when executed on a single CPU. If 20% of this computation is strictly sequential, then theoretically the best possible elapsed times for this program running on 2 CPUs and 4 CPUs respectively are
(A) 55 and 45 seconds
(B) 80 and 20 seconds

(C) 75 and 25 seconds
(D) 60 and 40 seconds


Answer: (D)

Explanation: Explanation: 2 Processors: 20 % of sequential work is done by processor p1 and remaining 80 % of work can be distributed among p1 and p2 equally. so time required = 20 + 40 = 60 seconds
4 Processors: 20 % of work is done by any of the processor sequentially and remaining 80 % of work can be divided among 4 processors, so maximum time required = 20 + 20 = 40 seconds

Option (D) is correct.


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Last Updated : 19 Nov, 2018
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