Search results
Results from the WOW.Com Content Network
The elevator algorithm, or SCAN, is a disk-scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests.. This algorithm is named after the behavior of a building elevator, where the elevator continues to travel in its current direction (up or down) until empty, stopping only to let individuals off or to pick up new individuals heading in the ...
The cost is predictable, as every time database system needs to scan full table row by row. When table is less than 2 percent of database block buffer, the full scan table is quicker. Cons: Full table scan occurs when there is no index or index is not being used by SQL. And the result of full scan table is usually slower that index table scan.
The LOOK algorithm, similar to the SCAN algorithm, honors requests on both sweep directions of the disk head, however, it additionally "looks" ahead to see if there are any requests pending in the direction of head movement. If no requests are pending in the direction of head movement, then the disk head traversal will be reversed to the ...
N-Step-SCAN (also referred to as N-Step LOOK) is a disk scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests. It segments the request queue into subqueues of length N .
Prefix sums are trivial to compute in sequential models of computation, by using the formula y i = y i − 1 + x i to compute each output value in sequence order. However, despite their ease of computation, prefix sums are a useful primitive in certain algorithms such as counting sort, [1] [2] and they form the basis of the scan higher-order function in functional programming languages.
In the case of Euclidean space, this approach encompasses spatial index or spatial access methods. Several space-partitioning methods have been developed for solving the NNS problem. Perhaps the simplest is the k-d tree , which iteratively bisects the search space into two regions containing half of the points of the parent region.
A simple and inefficient way to see where one string occurs inside another is to check at each index, one by one. First, we see if there is a copy of the needle starting at the first character of the haystack; if not, we look to see if there's a copy of the needle starting at the second character of the haystack, and so forth.
Shortest seek first (or shortest seek time first) is a secondary storage scheduling algorithm to determine the motion of the disk read-and-write head in servicing read and write requests. Description [ edit ]