If a parallel algorithm consists of a fully parallel part and
a fully serial part such that the fraction of instructions
that are fully serial is given by f , then the speedup
for this parallel algorithm can be given by:
tp = ((1-f)/p + f)*t1
In other words speedup is given by
S = 1/((1-f)/p + f).
Taking the limit as p increases to infinity gives an upper bound on speedup such that
S <= 1/f