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May/June 2011 Past paper - Q5

Posted by Vampyre 
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Vampyre
May/June 2011 Past paper - Q5
October 26, 2011 10:09AM
hi guys/gals,

any one manage question 5 of this paper or have any thoughts on it ?
been looking at it for a while and getting no where :-(

any help advice is welcome...
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Justice
Re: May/June 2011 Past paper - Q5
October 26, 2011 10:28AM
At the bottom of S1's tut 102 there's a whole example of almost the exact same question.
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quintonnel
Re: May/June 2011 Past paper - Q5
October 26, 2011 10:32AM
Or.....

Tut 102, page 9, Section 4. Page Replacement....
to be excact.

grinning smiley
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hexium
Re: May/June 2011 Past paper - Q5
October 26, 2011 02:32PM
What was your reduced string?
Mine was 0,1,2,0,3,1,3,2,0,4,3
What page fault rates did you get for a) FIFO, b) LRU and c) Optimal?
I got a) 6/11 b) 9/11 and c) 6/11

(c) has me worried since it sounds as if it should be the lowest of the lot.
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wishblade
Re: May/June 2011 Past paper - Q5
October 26, 2011 02:48PM
I got the same reduced string. Haven't done the page fault calculation yet - will get to it shortly and post back then.

The optimal replacement will be the lowest, but its not to say that in some situation the fault rate of another algorithm will produce the same rate as the optimal rate. Optimal is just going to be the lowest in every situation.

EDIT:
Yep, same fault rates as well...
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takadiyi
Re: May/June 2011 Past paper - Q5
October 26, 2011 06:23PM
I haven't as yet tackled Q5, but from what I understand and the exercises done so far on Page replacement. Optimal replace should have the lowest fault rate.
Guess there is no need to worry @hexium smile
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hexium
Re: May/June 2011 Past paper - Q5
October 26, 2011 06:35PM
Yes, I already confirmed with the lecturer. What was worrying me was that even my page faults were happening in exactly the same spots so for all intends and purposes, the FIFO and Optimal tables looked like I had just copied the one from the other.
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quintonnel
Re: May/June 2011 Past paper - Q5
October 26, 2011 08:44PM
Q3.4

I get that the process cannot be safely granted.
However it already fails at the comparison with the Need.
Is that really worth 6 marks?
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takadiyi
Re: May/June 2011 Past paper - Q5
October 26, 2011 10:12PM
Good luck everyone
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JessicaM
Re: May/June 2011 Past paper - Q5
October 26, 2011 10:59PM
@Takadiyi - Yes - Work = max resource vector. They should match. Check 3.3 again

3.3 last part for Process P3:

Work = (3, 15, 8, 10) + (0,2,1,0)
= (3, 17, 9, 10)
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