Question

Assume an algorithm takes 5.6 seconds to execute on a single 1.9 GHz processor. 20% of the algorithm is sequential. Assume that there is zero latency and that the remaining code exhibits perfect parallelism. How long (in seconds) should the algorithm take to execute on a parallel machine made of 3 1.9 GHz processors?

Answer 1

Answer:

2.6 seconds

Explanation:

We first start by calculating the speed up

The formula is given as:

n/1+(n-1)F

We have n = 3 which is the number of processors

F = 20% = percentage of algorithm

When we put values into the formula

3/1+(3-1)0.20

= 3/1+2*0.20

= 3/1+0.4

= 3/1.4

Speed up = 2.14

From here we calculate the expected time

T/speedups

= 5.6/2.14

= 2.6

Therefore the expected time is 2.6 seconds