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Exercise 1 - Amdahl's Law

A programmer is given the job to write a program on a computer with processor having speedup factor 3.8 on 4 processors. He makes it 95% parallel and goes home dreaming of a big pay raise. Using Amdahl’s law, and assuming the problem size is the same as the serial version, and ignoring communication costs, what is the speedup factor that the programmer will get?

Solution

Speedup formula as per Amdahl's Law,





N - no of processor = 4

f - % of parallel operation = 95%

Speedup = 1 / (1 - 0.95) + (0.95/4) = 1 / 0.5 + (0.95/4)

Speedup = 3.478

The programmer gets 3.478 as the speedup factor.

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