scholarly journals How Anomalous Is Beladv's Anomaly?

10.28945/3390 ◽  
2009 ◽  
Author(s):  
Kirby McMaster ◽  
Samuel Sambasivam ◽  
Nicole Anderson
Keyword(s):  
Computer Simulation ◽  
Virtual Memory ◽  
Memory System ◽  
Page Fault ◽  
String Length ◽  
Replacement Algorithm ◽  
Wide Range

In a virtual memory system using demand paging, the page fault rate of a process varies with the number of memory frames allocated to the process. When an increase in the number of frames allocated leads to an increase in the number of page faults, Belady's anomaly is said to occur. In this study we used computer simulation to examine four conditions that affect the incidence of Belady's anomaly: (1) page replacement algorithm (FIFO vs. Random Page), (2) process size, (3) reference string length, and (4) memory frames allocated to the process. We found that over a wide range of process sizes and reference string lengths, Belady's anomaly occurred for up to 58.6% of the (random) reference strings under FIFO, and up to 100% of the reference strings for Random Page. Under conditions where anomalies occur most often, the average frame allocation level was around 75% of the process size for FIFO, but just over 50% of the process size for Random Page. Throughout the study, Belady's anomaly occurred so frequently that it no longer seems anomalous. This is especially true for the Random Page algorithm.

Study of Page Replacement Algorithm Based on Experiment

2014 ◽  
Vol 530-531 ◽  
pp. 895-898
Author(s):  
Hong Wang
Keyword(s):  
Virtual Memory ◽  
Page Fault ◽  
Replacement Algorithm ◽  
Memory Control

The page replacement algorithm is an very important step which realize virtual memory control. A good page replacement algorithm can reduce the fault frequency when program executing, reduce the number of I/O, and then increase the systems efficiency effectively. In this paper, we studied the principle of various of page replacement algorithm, designed an program which simulated the procession and result of page replacement algorithm, in this program, we assume a few condition, record the experiment results. According to these data, we compared and analyzed the page fault and page fault frequency of different algorithm, and compare their performance.

scholarly journals Hybrid Page Replacement Algorithm in real time Operating System

2020 ◽  
pp. 433-439
Author(s):  
Pallab Banerjee ◽  
Biresh Kumar ◽  
Amarnath Singh ◽  
Shipra Sinha ◽  
Medha Sawan
Keyword(s):  
Operating System ◽  
Execution Time ◽  
Virtual Memory ◽  
Primary Memory ◽  
Page Fault ◽  
Secondary Storage ◽  
Real Time Operating System ◽  
Storage Devices ◽  
Replacement Algorithm ◽  
Replacement Technique

Programming codes are of variable length. When the size of codes becomes greater than that of primary memory, the concept of virtual memory comes into play. As the name suggests, virtual memory allows to outstretch the use of primary memory by using storage devices such as disks. The implementation of virtual memory can be done by using the paging approach. Allocation of memory frames to each and every program is done by the operating system while loading them into the memory. Each program is segregated into pages as per the size of frames. Equal size of pages and frames enhance the usability of memory. As, the process or program which is being executed is provided with a certain amount of memory frames; therefore, swap out technique is necessary for the execution of each and every page. This swap out technique is termed as Page Replacement. There are many algorithms proposed to decide which page needs to be replaced from the frames when new pages come. In this paper, we have proposed a new page replacement technique. This new technique is based on the approach of reading and counting of the pages from secondary storage. Whenever the page fault is detected, the needed page is fetched from the secondary storage. This process of accessing the disc is slow as compared to the process in which the required page is retrieved from the primary storage. In the proposed technique, the pages having least occurrence will be replaced by the new page and the pages having same count will be replaced on the basis of LRU page replacement algorithm. In this method, the paged are retrieved from the secondary storage hence, possibility of page hit will be increased and as a result, the execution time of the processes will be decreased as the possibility of page miss will be decreased.

scholarly journals An Improved Page Replacement Algorithm Using Block Retrieval of Pages

2018 ◽  
Vol 7 (4.5) ◽  
pp. 32 ◽  
Author(s):  
Govind Prasad Arya ◽  
Devendra Prasad ◽  
Sandeep Singh Rana
Keyword(s):  
Operating System ◽  
Execution Time ◽  
Virtual Memory ◽  
Primary Memory ◽  
Page Fault ◽  
Secondary Storage ◽  
Frame Size ◽  
Replacement Algorithm ◽  
Replacement Technique ◽  
Computer Programmer

The computer programmer write programming codes of any length without keeping in mind the available primary memory. This is possible if we use the concept of virtual memory. As the name suggests, virtual memory is a concept of executing a programming code of any size even having a primary memory of smaller size than the size of program to be executed. The virtual memory can be implemented using the concept of paging. The operating system allocates a number of memory frames to each program while loading into the memory. The programming code is equally divided into pages of same size as frame size. The size of pages and memory frames are retained equal for the better utilization of the memory. During the execution of program, every process is allocated limited number of memory frames; hence there is  a need of page replacements. To overcome this limitation, a number of page replacement techniques had suggested by the researchers. In this paper, we have proposed an modified page replacement technique, which is based on the concept of block reading of pages from the secondary storage. The disc access is very slow as compared to the access from primary memory. Whenever there is a page fault, the required page is retrived from the secondary storage. The numerous page faults increase the execution time of process. In the proposed methodology, a number of pages, which is equal to the allotted memory frames, are read every time when there is a page fault instead of reading a single page at a time. If a block of pages has fetched from secondary storage, it will definitely increases the possibilities of page hit and as a result, it will improve the hit ratio for the processes.  

scholarly journals A virtual memory system for a relational associative processor

1976 ◽  
Author(s):  
S. A. Schuster ◽  
E. A. Ozkarahan ◽  
K. C. Smith
Keyword(s):  
Virtual Memory ◽  
Memory System

OPTIMIZING OPERATION OF WASTEWATER TREATMENT PLANTS BY OFFLINE AND ONLINE COMPUTER SIMULATION

1994 ◽  
Vol 30 (2) ◽  
pp. 165-174 ◽  
Author(s):  
Ralf Otterpohl ◽  
Thomas Rolfs ◽  
Jörg Londong
Keyword(s):  
Computer Simulation ◽  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Historical Analysis ◽  
Computer Work ◽  
Biological Phosphorus Removal ◽  
Wide Range

Computer simulation of activated sludge plant for nitrogen removal has become a reliable tool to predict the behaviour of the plant Models including biological phosphorus removal still require some practical experience but they should be available soon. This will offer an even wider range than today's work with nitrogen removal. One major benefit of computer simulation of wastewater treatment plants (WTP) is the optimization of operation. This can be done offline if hydrographs of a plant are collected and computer work is done with “historical” analysis. With online simulation the system is fed with hydrographs up to the actual time. Prognosis can be done from the moment of the computer work based on usual hydrographs. The work of the authors shows how accuratly a treatment plant can be described, when many parameters are measured and available as hydrographs. A very careful description of all details of the special plant is essential, requiring a flexible simulation tool. Based on the accurate simulation a wide range of operational decisions can be evaluated. It was possible to demonstrate that the overall efficiency in nitrogen removal and energy consumption of ml activated sludge plant can be improved.

scholarly journals ДОСЛІДЖЕННЯ ПОКАЗНИКА ЕФЕКТИВНОСТІ ЕКСПЛУАТАЦІЇ ЗАСОБІВ ВИМІРЮВАЛЬНОЇ ТЕХНІКИ МЕТОДОМ КОМПʼЮТЕРНОГО МОДЕЛЮВАННЯ

2020 ◽  
pp. 166-169
Author(s):  
Олександр Володимирович Томашевський ◽  
Геннадій Валентинович Сніжной
Keyword(s):  
Computer Simulation ◽  
Distribution Function ◽  
Normal Distribution ◽  
Failure Rate ◽  
Random Variable ◽  
Operational Efficiency ◽  
Distribution Law ◽  
Maintenance System ◽  
Wide Range ◽  
Calibration Interval

The operational efficiency of measuring equipment (ME) is important in determining the cost of maintaining ME. To characterize the operational efficiency of the ME, an efficiency indicator has been introduced, an increase of which will reduce costs caused by the release of defective products due to the use of ME with unreliable indications. Over time, the ME parameters change under the influence of external factors and the ME aging processes inevitably occur, as a result of which the parameters of the ME metrological service system change. Therefore, in the general case, the parameters of the metrological maintenance system of ME should be considered as random variables. Accordingly, the efficiency indicator of measuring instruments is also a random variable, for the determination of which it is advisable to apply the methods of mathematical statistics and computer simulation. The performance indicator depends on the parameters of the metrological maintenance ME system, such as the calibration interval, the time spent by the ME on metrological maintenance, and the likelihood of ME failure-free operation. As a random variable, the efficiency indicator has a certain distribution function. To determine the distribution function of the efficiency indicator and the corresponding statistical characteristics, a computer simulation method was used. A study was made of the influence on the indicator of the effectiveness of the parameters of the metrological maintenance system ME (interesting interval, the failure rate of ME). The value of the verification interval and the failure rate of MEs varied over a wide range typical of real production. The time spent by ME on metrological services is considered as a random variable with a normal distribution law. To obtain random numbers with a normal distribution law, the Box-Muller method is used. After modeling, the statistical processing of the obtained results was done. It is shown that in real production, the efficiency indicator has a normal distribution law and the value of the efficiency indicator with an increase in the calibration interval does not practically change.

scholarly journals Application of Digital Cellular Radio for Mobile Location Estimation

1970 ◽  
Vol 2 (2) ◽  
Author(s):  
Farhat Anwar
Keyword(s):  
Computer Simulation ◽  
Geographical Area ◽  
Location Estimation ◽  
Cellular Radio ◽  
Mobile Location ◽  
Cellular Environment ◽  
Wide Range ◽  
Digital Cellular

The capability to locate the position of mobiles is a prerequisite to implement a wide range of evolving ITS services. Radiolocation has the potential to serve a wide geographical area. This paper reports an investigation regarding the feasibility of utilizing cellular radio for the purpose of mobile location estimation. Basic strategies to be utilized for location estimation are elaborated. Two possible approaches for cellular based location estimation are investigated with the help of computer simulation. Their effectiveness and relative merits and demerits are identified. An algorithm specifically adapted for cellular environment is reported with specific features where mobiles, irrespective of their numbers, can locate their position without adversely loading the cellular system.Key Words: ITS, GSM, Cellular Radio, DRGS, GPS.

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