cpu scheduling

Question

A process burst time can be using exponential averaging technique of shortest process next scheduling.

Assume E(t) is the estimation burst time of a process at time t , B(t) is the actual burst time of a process at time t , and 0<=α<=1.

What is the formula to predict the burst time of t?

a) E(t) = B(t) * α + (1 - α) * B(t - 1)

b) E(t) = α * E(t - 1) + (1 - α) * E(t - 2)

c) E(t) = B(t - 1) * α + (1 - α) * B(t - 2)

d) E(t) = α * E(t - 1) + (1 - α) * B(t - 1)

e) none

Answer 1

Ans should be d). You can refer Galvin for further reading. The variables have been changed but d formula for exponential averaging technique is same.

And d formula given in options somewhat resembles d one in Galvin. I hope d descp helps u. Okay. Pg no 156 for further reading.

Galvin: 7th Edition. :)

Comments

ok. thanks

Answer 2

should be e) none 

formula is $E\left ( t \right )=\alpha *\left ( B\left ( t-1 \right ) \right )+\left ( 1-\alpha \right )*E\left ( t-1 \right )$

Where ,

$E\left ( t -1\right )=\text{predicted burst time at time}  t-1$

$B\left ( t-1 \right )=\text{actual burst time at time }t-1$

Refer galvin page 191 here

http://www.uobabylon.edu.iq/download/M.S%202013-2014/Operating_System_Concepts,_8th_Edition%5BA4%5D.pdf