It has been suggested that this article or section be merged with Memory locality. (Discuss)

In computer science, locality of reference, sometimes also called the principle of locality, is a concept which deals with the process of accessing a single resource multiple times. There are three basic types of locality of reference: temporal, spatial and sequential: Wikipedia does not have an article with this exact name. ... Memory Locality is a term in computer science used to denote the temporal or spatial proximity of memory access. ... Computer science, or computing science, is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ...

Temporal locality

The concept that a resource that is referenced at one point in time will be referenced again sometime in the near future.

Spatial locality

The concept that the likelihood of referencing a resource is higher if a resource near it has been referenced.

Sequential locality

The concept that memory is accessed sequentially.

The reason these concepts are true is due to the manner in which computer programs are created. Generally, data that are related are stored in consecutive locations in memory. One common pattern in computing is that processing is performed on a single item and then the next. This means that if a lot of processing is done, the single item will be accessed more than once, thus leading to temporal locality of reference. Furthermore, moving to the next item implies that the next item will be read, hence spatial locality of reference, since memory locations are typically read in batches. A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... This article or section does not cite its references or sources. ... Originally, the word computing was synonymous with counting and calculating, and a science and technology that deals with the original sense of computing mathematical calculations. ...

Increasing and exploiting locality of reference are common techniques for optimization. This can happen on several levels of the memory hierarchy. Paging obviously benefits from spatial locality. A cache is a simple example of exploiting temporal locality, because it is a specially designed faster but smaller memory area, generally used to keep recently referenced data and data near recently referenced data, which can lead to potential performance increases. Data in cache does not necessarily correspond to data that is spatially close in main memory; however, data elements are brought into cache one cache line at a time. This means that spatial locality is again important: if one element is referenced, a few neighbouring elements will also be brought into cache. Finally, temporal locality plays a role on the lowest level, since results that are referenced very closely together can be kept in the machine registers. Programming languages such as C allow the programmer to suggest that certain variables are kept in registers. It has been suggested that Loop optimization be merged into this article or section. ... In computer operating systems, paging memory allocation (also called memory address translation) algorithms divide computer memory into small partitions, and allocate memory using a page as the smallest building block. ... Look up cache in Wiktionary, the free dictionary. ... This article or section should be merged with CPU cache. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ...

References

See also

• Burst mode (computing)
• Row-major order
• File system fragmentation

Burst mode (alternatively burst-mode, with an hyphen) is a generic computing term referring to any situation in which a device is transmitting data repeatedly without waiting for input from another device or waiting for an internal process to terminate before continuing the transfer of data. ... Row-major order describes a way to store a multidimensional array in linear memory. ... In computing, file system fragmentation, sometimes called file system aging, is the inability of a file system to lay out related data sequentially (contiguously), an inherent phenomenon in storage-backed file systems that allow in-place modification of their contents. ...

Bibliography

• Peter J. Denning The locality principle, 2005. The story of the computing fundamental principle of locality of reference.