Example Of Resource Allocation Process With Need Calculation

Allocation

Firstly calculated the need that is Maximum- Allocation

Now calculating that Po will execute or not; the need of P0 is compared with the available slot.

Need <= Available

1202<= 0222 (This is not true)

Thus, Po should wait

Now calculating that P1 will execute or not; the need of P1 is compared with the available slot.

Need <= Available

0132<= 0222 (This is true)

Thus, P1 is kept in safe state

Future calculating the work,

Work= Work + Allocation

Work (P1)= 0222+0121

            = 0343

P1 is executed

Now calculating that P2 will execute or not; the need of P2 is compared with the available slot.

Need <= Available

1102<= 0343  (This is not true)

Thus, P2 should wait

Now calculating that P3 will execute or not; the need of P3 is compared with the available slot.

Need <= Available

0220<= 0222 (This is true)

Thus, P3 is kept in safe state

Future calculating the work,

Work= Work + Allocation

Work (P3)= 0343+1210

            = 1553

P3 is executed

Now calculating that P4 will execute or not; the need of P4 is compared with the available slot.

Need <= Available

2005<= 1553 (This is not true)

Thus, P4 should wait

Now, again calculating that P0 will execute or not; the need of P0 is compared with the available slot.

Need <= Available

1202<= 1553 (This is true)

Thus, P0 is kept in safe state

Future calculating the work,

Work= Work + Allocation

Work (P0)= 1553+2012

            = 3565

P0  is executed

Now calculating that P2 will execute or not; the need of P2 is compared with the available slot.

Need <= Available

1102<= 3565 (This is true)

Thus, P2 is kept in safe state

Future calculating the work,

Work= Work + Allocation

Work (P2)= 3565+4003

            = 7568

P2 is executed

Now calculating that P4 will execute or not; the need of P4 is compared with the available slot.

Need <= Available

2003<= 7568(This is true)

Thus, P4 is kept in safe state

Future calculating the work,

Work= Work + Allocation

Work (P4)= 7568 + 1030

            = 8598

P4 is executed

Thus, the Sequence is P1 P3 P0 P2 P4

Answer 2: Program execution

The six steps are described as follows:

Use of MAR- It is used to hold the memory location of data so that it can be accessed whenever it is needed. It is a CPU register that stores the memory address from the data so that it can be fetched from the CPU.  

Maximum

Use of MBR- It contains the copy of memory location and copies the data item to MBR. It act as a buffer that allows the processor and memory units to act as independent units.

Answer 3: Page     replacement          

These algorithms are used to decide which page is needed to be replaced when new pages enters the system. Whenever new page enter the system and there is no memory available then page fault occurs (Lee, Bahn & Noh, 2014). Operating system then uses the existing page by replacing it with the new page. There are various page replacement algorithms that are available so that number of page faults gets reduced. The different page replacement algorithms that are available are:

• First in First Out- It is a simplest form of page replacement algorithm in which it keeps track of all the pages and keeps the oldest page at first position in the queue. When the queue is full and ne page enters the first page is replaced (Zhan, Zhang, Jiang, Yang, Li and Li, 2018).

Advantage and disadvantage- It is easy to understand but it is not very effective. It has a very slow process execution rate and also increases the chances of page fault (Tsai and Lei, 2017).

• Optimal Page replacement- It is an algorithm in which the page that has less probability of being used in future is replaced. It is used to set a benchmark so that other replacement algorithm can be compared and analysed (Zhan, Zhang, Jiang, Yang, Li and Li, 2018).

Advantage and disadvantage- It is useful as it has lowest page fault rate and it never suffers from the issue of Belady’s anomaly. It is difficult to implement and need future knowledge to take any actions.

• Least Recently Used- The page that is used very least is replaced with the new page. It uses the principal of locality like replacing the page which is less likely to be referenced in the near future (Tsai and Lei, 2017).

Advantage and disadvantage- It also never suffer from Belady’s anomaly and assembles full statically analysis (Wu,  Jin, Yang and Yue, 2014).

Task  2

Answer 1: Basic Terms

 Some of the terms are explained by considering one general human example is:

• Live lock- The concept of live lock is similar to deadlock; the only difference in live lock is that state of processes keeps on changing with respect to other processes (Hu, Neamtiu & Alavi, 2016). It is a case off resource starvation but it generally occurs when specific process is not progressing (Yu, Srisa-an, & Rothermel, 2017).

Example- The real life example of live lock is when two humans collide in a narrow corridor. There is a very little space for both the individuals to pass together from the corridor. But if both the individuals adjust a little by moving side the issue could be resolved (Gao & Xu, 2015). But while moving aside they end up swaying with each other without making any progress.

• Race    Condition- It is an unwanted condition that occurs when two or more operations are performed by the system at the same time. It causes can issues as a proper sequence needs to be followed for completing the operations correctly.  Apart from that in computer system this issue arise at the time of entering commands. The wrong sequence can overwrite the commands and may cause error (Qin & Jin, 2015).

Example- A human related example that can explain this situation is condition of light switch. In offices or homes, many light switches are connected from a same celling light. Thus, irrelevant position of the switches may cause wrong output. The problem will arise when two individuals are using the switch at the same time. Thus, their actions will cancel out and no result would be obtained.

• Deadlock- It is a situation when other the system requires the same resource at the same time. Deadlock is a condition that prevents both the user to access the resources. In terms of computer science, deadlock is a condition when two or more processes are waiting for the resource to be released by other process.

Example- The traffic of vehicles sometimes led to condition of deadlock.

As shown above, all the vehicle need to cross the way but waits for the other vehicle to clear the way. Thus, traffic gridlock is an everyday example of a deadlock situation.

Need

Answer 2: Concept        of      an     algorithm

An algorithm is a step by step procedure that is used to solve a particular problem. A computer program can also be viewed as an algorithm as it is a procedure that is used to resolve the problem. The concept of algorithms is widely used in all the sectors of information technology (Gatys, Ecker & Bethge, 2015). It can be said as a well-defined process that is adopted to solve a problem. It is an effective method that is used to express all the finite amount of space and time. An algorithm is mostly used in data processing, calculations and other computer related operations. An algorithm mainly manipulates the data so that repeated task can be performed by simply entering the input data.

It is a detail series of instructions that are used to solve the problem. In computers, algorithms are used to accomplish the task so that the task can be solved. It is a sequence of computational steps that are used to perform complex tasks (Gulshan, et. al, 2016). It can be said as a set of instructions that are designed to perform specific task. The methods of algorithm design form one of the core practical technologies of computer science and an algorithm can be specified by the algorithm. It is a synonym for finite computational method so that it fitness best in the property. They are created independently in more than one programming language (Wen, Shao, Xue & Fang, 2015).

Characteristics of an Algorithm

The algorithms are unambiguous in nature as all the inputs are clear so that it may lead to clear meaning. It has well defined inputs so that desired output could be obtained. One of the important characteristics is that algorithm should terminate after finite steps (Wen, Shao, Xue & Fang, 2015). 

Answer 3 : Round robin scheduling algorithm

Calculating Average waiting time

Given,

Quantum=25         time     units.  

 0           25          39           64          89        114        139         142         167       181       193     218        224

Average waiting time= Waiting time of all processes/ Number of processes

=131+75+75+ 53+0/5

=67.6

References

Gao, Q., & Xu, M. (2015). U.S. Patent No. 9,052,967. Washington, DC: U.S. Patent and Trademark Office.

Gatys, L. A., Ecker, A. S., & Bethge, M. (2015). A neural algorithm of artistic style. arXiv preprint arXiv:1508.06576.

Gulshan, V., Peng, L., Coram, M., Stumpe, M. C., Wu, D., Narayanaswamy, A., … & Kim, R. (2016). Development and validation of a deep learning algorithm for detection of diabetic retinopathy in retinal fundus photographs. Jama, 316(22), 2402-2410.

Hu, Y., Neamtiu, I., & Alavi, A. (2016, July). Automatically verifying and reproducing event-based races in android apps. In Proceedings of the 25th International Symposium on Software Testing and Analysis (pp. 377-388). ACM.

Lee, S., Bahn, H., & Noh, S. H. (2014). CLOCK-DWF: A write-history-aware page replacement algorithm for hybrid PCM and DRAM memory architectures. IEEE Transactions on Computers, 63(9), 2187-2200.

Qin, L. I. U., & Jin, C. H. E. N. (2015). Job-Shop Scheduling with Parallel Equipments Based on Five Dimensions Scheduling Algorithm. Journal of Jiangnan University (Natural Science Edition), 1, 010.

Tsai, H.B. and Lei, C.L., 2017, April. A page replacement algorithm based on frequency derived from reference history. In Proceedings of the Symposium on Applied Computing (pp. 1522-1527). ACM.

Wen, X., Shao, L., Xue, Y., & Fang, W. (2015). A rapid learning algorithm for vehicle classification. Information Sciences, 295, 395-406.

Wu, Z., Jin, P., Yang, C. and Yue, L., 2014, September. APP-LRU: a new page replacement method for PCM/DRAM-based hybrid memory systems. In IFIP International Conference on Network and Parallel Computing (pp. 84-95). Springer, Berlin, Heidelberg.

Yu, T., Srisa-an, W., & Rothermel, G. (2017). An automated framework to support testing for process?level race conditions. Software Testing, Verification and Reliability, 27(4-5), e1634.

Zhan, J., Zhang, Y., Jiang, W., Yang, J., Li, L. and Li, Y., 2018. Energy-aware page replacement and consistency guarantee for hybrid NVM–DRAM memory systems. Journal of Systems Architecture, 89, pp.60-72.

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