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+6 votes
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Consider the list of page references in the time line as below:

9  6  2  3  4  4  4  4  3  4  4  2  5  8  6  8  5  5  3  2  3  3  9  6  2  7

What is the working set at the penultimate page reference if ∆ is 5?

  1. {8, 5, 3, 2, 9, 6}
  2. {4, 3, 6, 2, 5}
  3. {3, 9, 6, 2, 7}
  4. {3, 9, 6, 2}
in Operating System by Boss (30.8k points) | 4.1k views
+1
@rude @dexter @shivanisrivarshini What do u think ?
0
which replacement algorithm is used ???
0
I guess its "Penultimate page reference", But I have no idea what it is.
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what is delta here
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delta is number of frames in frame set.
0
I'm not understood which replacement algorithm is to be taken ??
+1
d is correct option
0

working set at the penultimate(second from the last) page reference if ∆ is 5.

9 6 2 3 4 4 4 4 3 4 4 2 5 8 6 8 5 5 3 2 3 3 9 6 2 7

0
Please check my answer below

8 Answers

+13 votes
Best answer
Here Working set window Size=5=Delta

The working-set window is a moving window.

At each memory reference, a new reference appears at one end and the oldest reference drops off the other end.

A page is in the working set if it is referenced anywhere in the working-set window. (Galvin;;Don't worry read the last paragraph  to understand it simply)

 

Now As Told here penultimate reference (means except last reference) So take 5 page reference from end of the given list of references from the question except last reference. i.e.7 They are {3,3,9,6,2} in Working Set Window So the Working Set is {3,9,6,2}. So, option D is the Ans.

Note

Working Set Window::-- Examines the most recent Delta no. of page references.

Working Set::--Set of unique pages in most recent Delta page references.
by Boss (23.9k points)
selected by
+3

Here Working set window size=Delta=10

+8 votes
I think working set at the penultimate ( second from the last ) page reference would be

{3, 9, 6, 2 }

And finally at last

{ 3, 9, 6, 2, 7 }
by Boss (26.5k points)
edited by
0
if penultimate mean that your answer is correct and i assumed it as last working set
0
second last will be{2,3,6,9}
 so (D)isanswer
0

working set will be{3,9,6,2}
 so (D)isanswer

+1
sorry bro... now updated ..
+3 votes

Penultimate page reference means second last page reference. Hence answer will be D. (3,9,6,2)

 

Working sets are as below:

9 - {9}

6 - {9,6}

2 - {9,6,2}

3 - {9,6,2,3}

4 - {9,6,2,3,4}

4 - {6,2,3,4}

4 - {2,3,4}

4 - {3,4}

3 - {3,4}

4 - {3,4}

4 - {3,4}

2 - {3,4,2}

5 - {3,4,2,5}

8 - {2,4,5,8}

6 - {2,4,5,8,6}

8 - {2,5,8,6}

5 - {5,8,6}

5 - {5,8,6}

3 - {3,5,8,6}

2 - {2,3,5,8}

3 - {2,3,5}

9 - {2,3,9}

6 - {2,3,9,6}

2 - {3,9,6,2}

7 - {3,9,6,2,7}

by Active (3.3k points)
0
which algo u have used???
0
please explain ..m not getting how u got the sets
0
which algo??
0
0
....
+2 votes

Answer: option D

Penultimate means in second last working set model.

Please visit this link for more information.

http://cs.uttyler.edu/Faculty/Rainwater/COSC3355/Animations/workingset.htm

by (369 points)
+1 vote
no algo is given here but delta is 5 so choice a,d are out since they 6 and 4 frames respectively . in question they are asking the second last one working set . so if we apply fifo in the penultimate ref we will get 9 8 6 2 3 which is none of these even if we apply LRU AND OPT choice is none
by Boss (49.3k points)
0 votes
Option c is the answer .
by Loyal (9.9k points)
0
how r u getting?
0
Will message you it was complex to write :)
0
can u pls let me know the answer in details...Pls msg me if possible.
+1
0
Thank You. I understood.
0 votes

In FIFO C) is the answer

Last 5 frames in the page table {7,6,2,9,3}

by Veteran (119k points)
0
why u considered only FIFO ??
0
#clarification : working set means the remaining pages in the frame set, after we apply page replacement policy on given page ref sequence ?
0
@Lord yes

@shivani just trial and error
0
@srestha  even if you use FIFO penultimate page reference would be (9 8 6 2 3 ) na
0 votes

Working set window size = 5.

This doesn't mean there must be 5 page numbers in it always. At most 5.

When the second last reference is reached, the working-set windows has {3,3,9,6,2}

=> {3,9,6,2}

 

Option D

by Loyal (6.4k points)
Answer:

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