operating System

Question

Assume that a process has CPU burst time for last four runs as 3 sec, 4 sec, 5 sec and 3 sec (last). Given that last predict burst time was 4 sec and α = 0.6. The next predict of CPU burst time for process when CPU scheduler is shortest process next with exponential averaging is _________. in sec (upto 1 to decimal places).

Comments

I'm getting 3.4s

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can u provide the solution?

Answer 1

$\tau_{n+1} = \alpha t_n + (1 - \alpha) \tau_n$

where $\tau_{n+1}$ is the predicted value of the next CPU burst.

$0 \leq \alpha \leq 1$

$\tau_n$ is the predicted value of the last CPU burst (here $\tau_n$ = 4s), and

$t_n$ is the (actual) last run time of the process (here $t_n$ is 3s).

Putting these all,

$\tau_5$ = 0.6 * 3 + 0.4 * 4 = 1.8 + 1.6 = 3.4s

Comments

i think here u need to calculate for 4 sec than 5 sec than 3 sec .......not only one step

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To calculate $\tau_5$ we need $\tau_4$ and $t_4$, which are given, then why would we need to calculate $\tau_2$, $\tau_3$ and $\tau_4$? And even if you want to do that how would you do that, since $\tau_1$ is not given. Though you can calculate these going backward from $\tau_4$, but then there is no need to do that.

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yaa u right here ask about at tau(5)........kk  (3.4 is correct answer)