Assignment1 Q 4.1 RR

Does anybody disagree with the assignment solutions answer two the RR Gantt chart in question 4.1


Process Arrival time Burst time Priority
P1, 0, 4, 1,
P2, 5, 1, 3,
P3, 3, 10, 2,
P4, 10, 2, 4,
P5, 9, 5, 1,
P6, 13, 3, 3,

Do we take arrival times in account to set the order of the Processes?

If so then the FIFO order is P1, P3, P2, P5, P4, P6
So we start with P1. RR (quantum = 3) Shaded when done
(0)P1(3)P3(6)P2(7)P1(8)P3(11)P5(14)P4(16)P6(19)P3(22)P5(24)P3(25)
This answer is incorrect according to the assignment results.

If we do not reorder the processes according to arrival time the order of course is
P1, P2, P3, P4, P5, P6
So we start with P1. RR (quantum = 3) Shaded when done
(0)P1(3)P3(6)P1(7)P2(8)P3(11)P4(13)P5(16)P6(19)P3(22)P5(24)P3(25)
This answer is also incorrect according to the assignment results.

What am I missing?

And which procedure is correct the first or the second?

In the tutorial letter 102 there are no arrival times and thus that one is simple and works out.

I see the copy and past from word has lost my shading.

OK, never mind I have found my mistake. This question is tricky though for the RR chart.

The catch is not to look at all the processes that will be in the queue but only at those who are in the cue at time of arrival.

Yeah this was tricky. I think the key to that question was the fact that RR is preemptive, thus everytime a process arrives while anothers time quantum ends, it will prempt the last process.