Theorem 30.4

What if we do not have enough processors?

Theorem: If a p-processor PRAM algorithm runs in time t, then for any p' < p, there is a p'-processor PRAM algorithm A' for the same problem that runs in time O(pt/p').

Example: p=10, p'=5, A = O(t)

A' = O(10/5 t) = O(t)

Work(A) = Work(A')