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Amdahl Law

Maximum speedup from parallelizing a fraction of a task.

Formula

S=1(1−p)+p/sS = \frac{1}{(1-p) + p/s}

Variables

pParallel fraction
sSpeedup of that part

Example

Serial parts limit gains

Did You Know?

Amdahl's law dooms parallel computing: if a tenth of a task is sequential, even infinite cores give at most a tenfold speedup.

parallel