ISRO2015-13

Question

Six files $\text{F1, F2, F3, F4, F5}$ and $\text{F6}$ have $100, 200, 50, 80, 120, 150$ records respectively. In what order should they be stored so as to optimize act. Assume each file is accessed with the same frequency

• A. $\text{F3, F4, F1, F5, F6, F2}$
• B. $\text{F2, F6, F5, F1, F4, F3}$
• C. $\text{F1, F2, F3, F4, F5, F6}$
• D. Ordering is immaterial as all files are accessed with the same frequency.

Comments

what is the meaning of all files are accessed with same frequency?

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it uses B Tree to insert node...

Answer 1

This is basically optimal storage on tapes problem.Greedy apprach is used to solve this problem.The files are to be stored sequentially  on tape.To read a particular file we need to start from beginning of tape..here goal is to find such order of storage that cost to access file is minimum..in order to achieve the files are stored in increasing order of length

So in above eg files will be stored in order F3 F4 F1 F5 F6 F2

Comments

why ?

how  cost to access file will be minimum?

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If three files os size is like [1000, 30, 2]
To access the file having size 2 in a "tape" which read sequentially like our old audio cassette we need to read "unnecessarily" 1000 and 30 file sized also.

But if arrangement would be [2,30,1000] to read 2 bytes we just access it, no need to wait to skip over 1030 bytes to reach the required file.

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Why This Makes Sense

Since tapes (or sequential storage media) must be read from the start until the required file, placing smaller files first reduces the total cumulative “skipping” cost. For example, retrieving the smallest file F3 (50 records) doesn’t require traversing over much other data. If F2 (200) were first, you'd always read past a huge chunk before finding even the smallest file, increasing average access time per request

Answer 2

Using optimal merge pattern
Option A.

Answer 3

I think Option A

Since each file is accessible with same frequency.

Answer 4

F1,F2,F3,F4,F5,F6

Answer 5

Ans.A

Comments

answer is A.

Answer 6

For optimization of storage we can arrange the files in ascending order,i.e.,option A