S=(1−α)P+αGustafson's law states that the speed up, S, of a computation on P processors is given by the equation where α is a known constant related to the parallelizability. Which of the following expressions equals the increase in the number of processors needed for the speedup to increase by 1 ?Choose 1 answer:(A) 1−α(B) α−1α(C) 1−α1(D) α
Q. S=(1−α)P+αGustafson's law states that the speed up, S, of a computation on P processors is given by the equation where α is a known constant related to the parallelizability. Which of the following expressions equals the increase in the number of processors needed for the speedup to increase by 1 ?Choose 1 answer:(A) 1−α(B) α−1α(C) 1−α1(D) α
Start with Gustafson's Law: We start with Gustafson's law, which is given by the equation S=(1−α)P+α. We want to find the increase in the number of processors (δP) needed for the speedup (S) to increase by 1. Let's denote the initial speedup as S and the new speedup as S+1. We can set up two equations based on Gustafson's law for these two scenarios.
Set up Equations: For the initial speedup S, we have the equation S=(1−α)P+α.
Find ΔP: For the new speedup S+1, we have the equation S+1=(1−α)(P+δP)+α.
Subtract Equations: Now we want to find the value of δP that satisfies the increase of 1 in speedup. We subtract the first equation from the second to eliminate α and get an equation for δP.S+1−S=(1−α)(P+δP)+α−((1−α)P+α)
Simplify Equation: Simplifying the equation, we get:1=(1−α)P+(1−α)δP+α−(1−α)P−α
Cancel Terms: The terms (1−α)P and α cancel out on both sides, leaving us with: 1=(1−α)δP
Divide to Find Delta P: To find delta P, we divide both sides of the equation by (1−α):ΔP=(1−α)1
Match with Choices: We look at the given choices to find the one that matches our expression for δP. The correct choice is (C) 1−α1.