1, lru algorithm is a page replacement algorithm. For unused data blocks in memory, called LRU, the operating system will move them out of memory to make room for loading other data according to the data belonging to LRU.
2. This is the whole content of LRU algorithm. LRU approximation algorithm is an algorithm that has not been used recently. It adds a reference bit to each entry in the memory block table, and the operating system sets them to 0 periodically. When a page is accessed, the location is set to 1 by the hardware.
3.lru algorithm is a commonly used page replacement algorithm, which selects pages that have not been used for the longest time to be eliminated.
Programming FIFO page replacement algorithm code with C++ language
Write four permutation algorithms in c language: OPT, FIFO, LRU and LFU. Familiar with memory paging management strategy. Understand the algorithm of page replacement. Master common scheduling algorithms. According to this scheme, the algorithm can be simulated and realized. Exercise the ability to use knowledge and practice.
First, open visualC++0 in the computer, and input preprocessing command and main function: # includesdio.h/* function header: input and output header file */voidmain()/* empty type: main function */.
The page buffer algorithm (PB) does not know whether it is your PBA or an improved clock algorithm. As for the C program, I didn't. .
The number of physical page frames is 3, and there is no corresponding virtual page at the beginning. The order of virtual page access is 0, 1, 2, 0, 1, 3, 0, 3, 1, 3. How many pages are missing by using FIFO replacement algorithm? () The number of physical page frames is 4, and there is no corresponding virtual page at the beginning.
In addition, although the FIFO algorithm is simple to implement, it is not suitable for the actual running law of the process. Because the first page may also be the most frequently visited. Therefore, the performance of this algorithm is poor. Algorithm idea: The pages eliminated each time are the pages that have not been used for the longest time recently.
First-in first-out algorithm (FIFO) Least recently used algorithm (LRU) Least recently used algorithm (LFU) Hit ratio = 1- number of page failures/page address stream length Experimental preparation The program design of this experiment is basically based on the experimental content.
Page replacement algorithm in C language programming
Write four permutation algorithms in c language: OPT, FIFO, LRU and LFU. Familiar with memory paging management strategy. Understand the algorithm of page replacement. Master common scheduling algorithms. According to this scheme, the algorithm can be simulated and realized. Exercise the ability to use knowledge and practice.
You can write a structure first, including quantity and usage times. Then dynamically generate an array, and the array elements are structures. Then write two other functions. One calculates the number of interrupts, and the other performs page replacement. When detecting whether it is interrupted, you can loop through the dynamically generated array above.
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O (t+p+s) memmove: o (t-p) memcpy: o (s) final complexity o (t * p+2 (t+s))-o (n 2). You can see that the hotspot is in the strstr function. If kmp or similar matching algorithm is used to optimize to O(n), the complexity can be directly reduced to O(n).
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Page replacement algorithm
1, the clock permutation algorithm is a performance and overhead balancing algorithm.
2. Algorithm rule: Arrange all the pages that may be replaced into a circular queue (access bit, modify bit). First round: scan the first (0,0) page from the current position for replacement.
3. The number of physical page frames is 4, and there is no corresponding virtual page at the beginning.
4.lru algorithm is a page replacement algorithm. For unused data blocks in memory, called LRU, the operating system will move them out of memory to make room for loading other data according to the data belonging to LRU.
5. Set the location to 1 by hardware. After a period of time, by checking these bits, you can determine which pages have been used and which pages have not been used since they were last set to 0. A page with this bit 0 can be eliminated because it has not been visited recently.
6. First-in first-out page replacement algorithm (FIFO). First-in-first-out page replacement algorithm (FIFO) The page replacement algorithm will generate delay exceptions. The basic idea of FIFO page replacement algorithm is to replace the page that is first called into memory at a time, that is, to replace the page with the longest waiting time in memory.
C++ programming, clock replacement algorithm
Clock () is a timing function in C/C++, and its related data type is clock _ t. In MSDN, Chad defines the clock function as follows: clock _ tclock (void); Simply put, it takes CPU time from program startup to function call.
Step 1: Scan the queue circularly from the starting position, find the first face with A=0 and M = 0, and replace it immediately. In addition, the access bit A does not change during the first scan.
Clock_t is actually very long, that is, long shaping. The return value of this function is the number of hardware clock cycles, which needs to be divided by CLK_TCK or CLK _ TCK clock _ per second to be converted into seconds or milliseconds.
The performance of clock algorithm is close to LRU, and the clock algorithm can be made more effective by increasing the number of bits used. An improved clock replacement algorithm is obtained by adding a modified bit on the basis of using bits.
while(clock()-now clocks _ PER _ SEC)； Note that there is a semicolon after it, which is an empty loop.
In addition to the best replacement, FIFO, LRU, clock, LFU and PBA, there are also page replacement algorithms in the operating system. ...
The page buffer algorithm (PB) does not know whether it is your PBA or an improved clock algorithm. As for the C program, I didn't. .
Optimal replacement algorithm (OPT), first-in first-out replacement algorithm (FIFO), least recently used replacement algorithm (LRU), clock replacement algorithm, least used replacement algorithm (LFU), page caching algorithm (PBA), etc.
The simplest page replacement algorithm is the first-in first-out (FIFO) method. The essence of this algorithm is to always choose the page that stays in main memory for the longest time (that is, the oldest page), that is, the page that enters memory first and then exits memory.
Common page replacement algorithms are FIFO, LRU and so on. Data transmission between external memory and internal memory: when a page is interrupted and needs to be transmitted from external memory to internal memory, a lot of data transmission is needed. In order to improve efficiency, operating systems usually use technologies such as pre-reading to speed up data transmission.
Commonly used page replacement algorithms include OPT, FIFO, LRU, Clock, LFU, PBA, etc.