Editing Hash function (section)

=== Specialized uses ===
Hash functions are also used to build [[cache (computing)|caches]] for large data sets stored in slow media. A cache is generally simpler than a hashed search table, since any collision can be resolved by discarding or writing back the older of the two colliding items.<ref>{{Cite web|last=Stokes|first=Jon|date=2002-07-08|title=Understanding CPU caching and performance|url=https://arstechnica.com/gadgets/reviews/2002/07/caching.ars|access-date=2022-02-06|website=Ars Technica|language=en-us}}</ref>

Hash functions are an essential ingredient of the [[Bloom filter]], a space-efficient [[Probability|probabilistic]] [[data structure]] that is used to test whether an [[element (mathematics)|element]] is a member of a [[set (computer science)|set]].

A special case of hashing  is known as [[geometric hashing]] or the ''grid method''. In these applications, the set of all inputs is some sort of [[metric space]], and the hashing function can be interpreted as a [[partition (mathematics)|partition]] of that space into a grid of ''cells''. The table is often an array with two or more indices (called a ''[[grid file]]'', ''grid index'', ''bucket grid'', and similar names), and the hash function returns an index [[tuple]].  This principle is widely used in [[computer graphics]], [[computational geometry]], and many other disciplines, to solve many [[proximity problem]]s in the [[Plane (geometry)|plane]] or in [[three-dimensional space]], such as finding [[closest pair problem|closest pairs]] in a set of points, similar shapes in a list of shapes, similar [[image processing|images]] in an [[image retrieval|image database]], and so on.

Hash tables are also used to implement [[associative array]]s and [[set (abstract data type)|dynamic sets]].<ref name="handbook_of_applied_cryptography">{{cite book|title=Handbook of Applied Cryptography|first1=Alfred J.|last1=Menezes|first2=Paul C.|last2=van Oorschot|first3=Scott A|last3=Vanstone|year=1996|publisher=CRC Press|isbn=978-0849385230|url-access=registration|url=https://archive.org/details/handbookofapplie0000mene}}</ref>