Sign In

Communications of the ACM

Research highlights

Technical Perspective: Building a Better Hash Function


Hashing is everywhere. To Start, hash tables are one of the most widely used primitive data structures, with numerous variations (open address, chained, linear probing, multiple-choice, cuckoo, and so on). Hashing is also frequently used for sampling; hash all items and keep only those with certain hash values as the sample. Hashing further plays a major role in a variety of algorithms and data structures for data sketches for both streaming and non-streaming data, such as Bloom filters and approximate counting structures.

For much of the early history of hashing, there was a clear divide between theory and practice. The mathematical analysis of hashing and hashing algorithms was (and often still is) based on perfect randomness. You assume that for each input x, the hash value h(x) is uniformly distributed over all possible values it could take on, and that each value h(x) is independent of all other hash values h(y) for yx. Such perfect hash functions make mathematical analysis much simpler, as every new hash value looks completely random.


 

No entries found

Log in to Read the Full Article

Sign In

Sign in using your ACM Web Account username and password to access premium content if you are an ACM member, Communications subscriber or Digital Library subscriber.

Need Access?

Please select one of the options below for access to premium content and features.

Create a Web Account

If you are already an ACM member, Communications subscriber, or Digital Library subscriber, please set up a web account to access premium content on this site.

Join the ACM

Become a member to take full advantage of ACM's outstanding computing information resources, networking opportunities, and other benefits.
  

Subscribe to Communications of the ACM Magazine

Get full access to 50+ years of CACM content and receive the print version of the magazine monthly.

Purchase the Article

Non-members can purchase this article or a copy of the magazine in which it appears.
Sign In for Full Access
» Forgot Password? » Create an ACM Web Account
ACM Resources