# Amdahl's Law

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vCalc.Amdahl's Law
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The Amdahl's Law calculator computes the speedup of the execution of a task based on the speed up factor (s) of the improvable portion of the task and the proportion (p) of the task that can be improved.

INSTRUCTIONS: Enter the following:

• (S) The speedup of the part of the task that can be improved.
• (P) The proportion (%) of the execution time that can be improved.

Speedup (v): The calculator returns the theoretical speedup of the whole task.

#### The Math / Science

Amdahl's law is a model for the relationship between the expected speedup of parallelized implementations of an algorithm relative to the serial algorithm, under the assumption that the problem size remains the same when parallelized." {wikipedia} This equation computes the speedup achievable from an improvement to a computation that affects a proportion P of that computation where the improvement has a speedup [factor] of S.  The Amdahl's formula for speedup is:

v = 1 /( (1-P) + P/S)

where:

• v = speedup factor
• P = portion of the task accelerated
• S = speedup for the portion