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A particular parallel program computation requires 100 sec when executed on a single processor. If 40% of this computation is inherently sequential (i.e. will not benefit from additional processors), then theoretically best possible elapsed times of this program running with 2 and 4 processors, respectively, are

A particular parallel program computation requires 100 sec when executed on a single processor. If 40% of this computation is inherently sequential (i.e. will not benefit from additional processors), then theoretically best possible elapsed times of this program running with 2 and 4 processors, respectively, are Correct Answer 70 sec and 55 sec

Data:

Computation time of single processor = 100 sec

Computation which is inherently sequential = 40%

Calculation:

40% sequential = 0.4 × 100 = 40 seconds  (for both 2 and 4 processors)

For two processor

Remaining 60% is divided by the 2 processors, that is, 30% and 30%

Computation of one processor = 0.3 × 100 = 30 seconds

Computation time = 40 + 30 = 70 // processors run in parallel manner

For four processor

Remaining 60% is divided by the 4 processors, that is, 15%, 15% 15% and15%

Computation of one processor = 0.15 × 100 = 15 seconds

Computation time = 40 + 15 = 55 // processors run in parallel manner

Therefore, theoretically best possible elapsed times of this program running with 2 and 4 processors is 70 sec and 55 sec.

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