So due the
communication cost the speed-up is always less than equal the
number of processors used in parallel computer.
According to the Amdahl’s law [3], it is very difficult to get
ideal parallel system to get the value of Sp is equal to p due to
the presence of some sequential code which can not be
parallelized and must be processed sequentially by a single
processor. Suppose r is the part of a program that can be
parallelized and the rest s = 1-r part is sequential in nature. Then
the speed up becomes