Ideally, given a set of distinct keys, , the set of hash values contains no duplicates. In practice, unless we know something about the keys chosen, we cannot guarantee that there will not be collisions. However, in certain applications we have some specific knowledge about the keys that we can exploit to reduce the likelihood of a collision. For example, if the keys in our application are telephone numbers, and we know that the telephone numbers are all likely to be from the same geographic area, then it makes little sense to consider the area codes in the hash function, the area codes are all likely to be the same.

Copyright © 1997 by Bruno R. Preiss, P.Eng. All rights reserved.