GATE 2024 CS (CS1) – Question 55
The baseline execution time of a program on a 2 GHz single core machine is 100 ns. The code corresponding to 90% of the execution time can be fully parallelized. The overhead for using an additional core is 10 ns when running on a multicore system. Assume that all cores run their share of the parallelized code for an equal amount of time. The number of cores that minimize the execution time of the program is ________
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Correct answer: 3
Explanation
Time(n)=10+90/n+10(n−1) for n cores. Minimizing: derivative gives n=√9=3. T(3)=10+30+20=60 ns, the minimum.