Amdahl’s law gives the theoretical speedup in latency of the

execution of a task at fixed workload.

It gives the formula to compute the theoretical maximum speed up

that can be achieved by providing multiple processors to an

application.

If S is the theoretical speedup then the formula is:

S(n) = 1 / (B + (1-B)/n)

where n is the number of processors

B is the fraction of the program that cannot be executed in parallel.

When n converges against infinity, the term (1-B)/n converges

against zero. Therefore, the formula can be reduced in this special

case to 1/B.

In general, the theoretical maximum speedup behaves in inverse

proportion to the fraction that has to be executed serially. This

means the lower this fraction is, the more theoretical speedup can

be achieved