Question

Problem D. Consider the exponential average formula used to predict the length of the next CPU burst. Associate the following implications a) through e) with assigning the values in 1) and 2), respectively, to the parameters used by the algorithm.

a) the most recent burst of the process is given much more weight than the past history associated with the process.

b) none of the previous bursts of the process is taken into consideration at all for predicting the length of the next CPU burst.

c) the formula always makes a prediction of 150 milliseconds for the next CPU burst.

d) after a couple of CPU bursts, the initial prediction value (150 milliseconds) has little impact on predicting the length of the next CPU burst.

e) the scheduling algorithm is almost memoryless and simply uses the length of the previous burst as the predicted length of the next CPU burst for the next quantum of CPU execution.

1) α = 0 and τ0 = 150 milliseconds ___________________________

2) α = 0.99 and τ0 = 150 milliseconds ___________________________

Answer 1

(1)

When,

, The equation will be as below:

Therefore, formula will always makes it's prediction of 150 milliseconds for upcoming/next CPU Burst.

(2)

When,

, The equation is as below:

Here, The most recent behaviour of the process i.e, has given extremely high weightage (approx 99% compared to approx 1.5%) than the past history of the process .