Philadelphia University
Lecturer: Dr. Nameer N. EL-Emam
Internal Examiner: Dr. Raad Alwan
Module Name: Adv.Operating System
Module Number: 750434
Second Exam
14/5/2015
Faculty of Information Technology
Department of CS
Marking Scheme
Semester two 2014-2015
One hour
Basic Part
Objective: The aim of this part is to check student abilities to understand the basic of Processors allocation algorithm in DOS.
Q1(5 marks) / Bidding algorithm tries to turn the computer system into a small economy, processors picking the highest bid
from all bids sent before. Answer the following:
a) What is the benefit of selecting the highest bid?
b) What is the expected system performance if a processor selects a bid randomly?
c) What is your suggestion to improve the bidding algorithm if we have more than one highest bid?
d) Some time the kernel increases or decreases the process’s bid with respect to the time. Explain the circumstances for this
dynamic bedding.
Ans:
A) Processors, which auction their cycles off to the highest bidder to gain high profit. If
we select bids randomly then the processor profit will be down.
B) The benefit of selecting the highest bids is to assign the process to the most proper
processor with respect to many features (speed, memory size, presence of floatingpoint hardware, and other features).
C) If we have more than one highest bids, scheduling all bids with the same level in the
one queue of selected processor according to the policy FCFS to avoid starvation,
or assign the equivalence bids to different processors with the same features.
D) The kernel increases or decreases the process’s bid with time due to the amount of
available resources in the system that are needs by process. Where the amount of
resources are changed through the time, and if we have enough resources then the
process’s bid is high.
Q2(5 marks) / Find the objective function of the figure below using Bokhari's algorithm.
The edge (e) in the processes graph has two weights, w1(e) and w2(e). Calculate the values of two weights of the above
processes graph.
OF= max(6+7, 2+8+9) + 3
= max(23,19)+3=19+3= 22
3
w1(e)   Sm  y  2  8  y  10
m 1
process 1 can move to P 2 then y  6
 w1(e)  6  10  16
w 2( e )  C 3  3
Familiar Part
Objective: The aim of this part is to check student abilities to understand processors’ scheduler and process policy algorithms in
DOS.
Q3(5 marks) / Let us define the following information of six processes working on two parallel processors. Apply ELS and ETS
to show the time analysis of each processor with load balance and minimum time (if possible)
Unfamiliar Part
Objective: The aim of this part is to check student abilities to compute the system performance in DOS.
Q4(5 marks)/ Assume we have application run on 10 processors with the total computation time of the concurrent portion is
equal to 50 sec. Compute the optimal sequential processing time if the optimal concurrent processing time at ideal system is
equal 20 sec. and the ratio of the total computation time needed for parallel algorithm to the time for the optimal sequential
algorithm is 10.
According to above given data then,
-
n=10 processors
-
total computation time of the concurrent portion =
-
optimal concurrent processing time at ideal system is OCPTID=20 sec
-
RP is the ratio of the total computation time needed for parallel algorithm to the time for the optimal sequential
algorithm is =10
-
Find optimal sequential processing time OSPT

p
i
OSPT
OSPT 
 RP
p
RP
i

50
5
10
OR
p
i
OSPT
OCPTid  n

n
OCPTid
RP
  pi



 OCPTid  n

OSPT  
 n   OCPTid
RP




 50



  20  10  10   20  5
 10





p
i
 50 sec