A program consumes 10 seconds when it runs on a single core

A program consumes 10 seconds when it runs on a single core processor. When the number of cores is increased, the program execution time is reduced to 6 seconds (2 of them are consumed by the sequential part of the program).

a) What is the number of cores?

b) What is the maximum theoretical speed up if we increase the number of cores?

Solution

number of cores required 5 then 5*2_4=6seconds

4 seconds work cannot be parallalized

so p=6/10=0. 6

maximum theoritical speed up =1/(1_p)=1/0. 4=2.5

amdahls law