21-05-2012, 02:49 PM
Hashing Algorithm
Hashing (1).ppt (Size: 422 KB / Downloads: 124)
Hashing function
It is usually better to treat v as a sequence of bytes and do one of the following for f(v):
(1) Sum or multiply all the bytes. Overflow can be ignored
(2) Use the last (or middle) byte instead of the first
(3) Use the square of a few of the middle bytes
Implementing hashing
The following operations are usually provided by an implementation of hashing:
(1) Initialization
(2) Insertion
(3) Retrieval
(4) Deletion
Minimal perfect hash functions
Minimal perfect hash function (MPHF) is a perfect hash function with the property that is hashed m keys to m buckets with no collisions
Cichelli(1980) and of Cercone et al.(1983) proposed two important concepts:
(1)using tables of values as the parameters
(2)using a mapping, ordering, and searching (MOS) approach