![]() ![]() (In the event that we ignore the first three, which all algorithms must endure, at that point optimal replacement is twice as good as FIFO replacement.) In fact, no replacement algorithm can process this reference string in three frames with fewer than nine faults. ![]() With just nine-page faults, optimal page replacement is obviously superior to a FIFO algorithm, which results in fifteen faults. The reference to page 3 replaces page 1, as page 1 will be the last of the three pages in memory to be referenced again. The reference to page 2 replaces page 7 because page 7 will not be used until reference 18, whereas page 0 will be used at 5, and page 1 at 14. Initially the first three references cause (pre-defined number of page frames) faults that fill the three frames that are empty. For instance, on our example reference string, the optimal page-replacement algorithm would yield nine-page faults, as to represent in Figure 1. It is just this: “Replace the page that won’t be utilized for the longest time frame.” Optimal page replacement algorithmīy utilizing optimal page-replacement algorithm ensure the most minimal conceivable page fault rate for a fixed number of frames. Optimal page replacement is such an algorithm does exist and has been called OPT or MIN page replacement algorithm. The Optimal page-replacement algorithm has the most reduced page-fault rate overall page replacement algorithms and it will never suffer from the effect of Belady’s anomaly.
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