Homework #5

• Assigned Nov. 27, due by Dec. 4
• 1.Consider a system modeled as below. A user request submitted to the system must queue for memory, and may begin processing (in the central subsystem) only when it has obtained a memory partition.
• (a)If there are 100 active users with 20 second think times, and system response time (the sum of memory queueing and central subsystem residence times) is 10 seconds, how many customers are competing for memory on average ?
• (b)If memory queueing time is 8 seconds, what is the average number of customers loaded in memory ?
• 2.An installation with a CPU intensive workload is considering moving from a centralized system with a single large CPU to a decentralized system with several smaller CPUs.
• (a)Suppose that 10 processors each 1/20-th the speed of the large processor can be operated at the same cost as the large processor. Use asymptotic throughput and response time bounds to investigate the conditions under which such a change clearly would be beneficial or detrimental (considering performance issues only).
• (b)Suppose that 15 processors each 1/10-th the speed of the large processor can be operated at the same cost. How does this affect your answer to (a) ?
• 3. Read the paper, especially the first three pages, "Design and Performance Tradeoffs in Clustered Video Servers," IEEE International Conference on Multimedia Computing and Systems 1996 (ICMCS'96) by R. Tewari, R. Mukherjee, D.M. Dias, and H.M. Vin. Summarize the presented web server model with the parameters/factors and their assumptions. They resort to simulation to analyze the model. Explore the possibility of analyzing the model based on queueing analysis or bound analysis.

Quiz #3

• Nov. 27, Mon.
• Read the paper "Mobile Users: To Update or not to Update ?" (1996) by A. Bar-Noy, I. Kessler, M. Sidi, and discuss the advantages and disadvantages of the ring cellular topology ? What if we use mesh topology instead of ring cellular topology ? Try to analyze the performance (expected number of update messages and expected number of searches) with the mesh topology in case of distance-based scheme.

Homework #4

• Assigned on Nov. 15, due by Nov. 22
• 1. Exercise 31.1
• 2. Read the following paper and answer the questions.
• A. Bhattacharya and S. K. Das, "LeZi-Update: An Information-Theoretic Approach to Track users in PCS Networks," ACM/IEEE International Conference on Mobile Computing and Networking (MobiCom'99)
• (i) Explain four mobility models described in section 4. What are the assumptions and how to obtain the parameters ?
• (ii) What are the advantages and disadvantages of the four models ?

Quiz #2

• Nov. 1 Wed.
• Queueing theorists use a shorthand notation called the Kendall notation in the form of A/S/m/B/K/SD. But most of the cases they use a shorter notation A/S/m, where A is the inter-arrival time distribution, S is the service time distribution and m is the number of servers. If >m, where  is the mean arrival rate,  is the mean service rate, and m is the number of servers, then what will happen to the queue and the system ?

Homework #3

• Assigned on Oct. 30, due by Nov. 11
• 1.Exercise 27.1.
• 2.Exercise 28.1 (a). Write a simple program to generate 100 random numbers and confirm that the numbers follow the specified distribution using C-S and K-S test.
• 3.Exercise 28.1 (b). Do not use f(x)=c, where c is a constant. Write a simple program to generate 100 random numbers and confirm that the numbers follow the specified distribution using spectral test.
• 4. Exercise 29.1

Quiz #1

• Oct. 25 Wed.
• A random variate has the following triangular density: f(x) = min(x, 2-x), 0<=x<=2. Develop algorithms to generate this variate via inverse transformation. Explain why the inverse transformation works.

Homework #2

• Assigned on Oct. 4 Wed., due on Oct. 25 Wed.
• Multimedia computing has changed the dominant applications from document-oriented to graphic or video-oriented. People resort to multimedia data since they are far more effective to present something compared to traditional text-based data. However, most of computer systems have not been re-designed to reflect the changes. One exceptional try is to incorporate multimedia instructions embedded in the processor, for example, Intel MMX (multimedia extension).
• Our company (Boom.com) tries to find the changes in operating system operations due to the multimedia environment. Especially, we want to look at the changes in process lifetime and memory usage, and of course their correlation. Based on the observations, we will develop a multimedia-oriented operating system that efficiently executes multimedia applications. We are sure that some embedded devices, which are dedicated to one or two multimedia applications, will benefit a lot out of this development.
• Your job is to incorporate some monitoring code in Linux operating system, gather information on process lifetime and memory usage, and obtain statistics. The report has to explain how you gather the information in general, and how the multimedia environment is simulated. You have to make some assumptions whenever necessary as this assignment does not describe the problem in detail.

Homework #1

• Assigned on Sep.18 Mon., due on Sep.25 Mon.
• Write a paper summary in one single-space page.
• Papers are selected from 1st Workshop on Feedback-Directed Optimization (FDO) & 2nd Workshop