computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...

, frecency is any

heuristic A heuristic (; ), or heuristic technique, is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediate, ...

that combines the frequency and

recency Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst. The term was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that r ...

into a single measure.

Heuristic

In its simplest form, the frequency and recency rating can be added to form a frecency rating. The ratings can be found by sorting items by most recent and most frequent respectively. A decayed calculation using

logarithms In mathematics, the logarithm is the inverse function to exponentiation. That means the logarithm of a number to the base is the exponent to which must be raised, to produce . For example, since , the ''logarithm base'' 10 o ...

can also be used.

Examples

Some web browsers use frecency to predict the likelihood of revisiting a given web page or reusing a given

HTTP cache The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, w ...

entry "Frecency is a score given to each unique

URI Uri may refer to: Places * Canton of Uri, a canton in Switzerland * Úri, a village and commune in Hungary * Uri, Iran, a village in East Azerbaijan Province * Uri, Jammu and Kashmir, a town in India * Uri (island), an island off Malakula Islan ...

in Places, encompassing bookmarks, history and tags. This score is determined by the amount of revisitation, the type of those visits, how recent they were, and whether the URI was bookmarked or tagged." Frecency can be computed from a list of use dates, either as pro-actively while a user browses the web or as needed. Some frecency measures can also be computed in a rolling manner without storing such a list. The

ZFS ZFS (previously: Zettabyte File System) is a file system with volume management capabilities. It began as part of the Sun Microsystems Solaris operating system in 2001. Large parts of Solaris – including ZFS – were published under an ope ...

filesystem uses this concept in its adaptive replacement cache (ARC) cache with a most recently used (MRU) and most frequently used (MFU) list.

References

{{Reflist Heuristics Measurement Web browsers Internet terminology