computer programming Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as anal ...

, an Iliffe vector, also known as a display, is a data structure used to implement multi-dimensional

arrays An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

. An Iliffe vector for an ''n''-dimensional array (where ''n'' ≥ 2) consists of a vector (or 1-dimensional array) of pointers to an (''n'' − 1)-dimensional array. They are often used to avoid the need for expensive multiplication operations when performing address calculation on an array element. They can also be used to implement

jagged array In computer science, a jagged array, also known as a ragged array, irregular array is an array of arrays of which the member arrays can be of different lengths, producing rows of jagged edges when visualized as output. In contrast, two-dimensio ...

s, such as

triangular array In mathematics and computing, a triangular array of numbers, polynomials, or the like, is a doubly indexed sequence in which each row is only as long as the row's own index. That is, the ''i''th row contains only ''i'' elements. Examples Notable ...

s, triangular matrices and other kinds of irregularly shaped arrays. The data structure is named after John K. Iliffe. Their disadvantages include the need for multiple chained pointer indirections to access an element, and the extra work required to determine the next row in an ''n''-dimensional array to allow an optimising compiler to prefetch it. Both of these are a source of delays on systems where the CPU is significantly faster than main memory. The Iliffe vector for a 2-dimensional array is simply a vector of pointers to vectors of data, i.e., the Iliffe vector represents the columns of an array where each column element is a pointer to a row vector. Multidimensional arrays in languages such as

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

(multidimensional lists),

Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...

Visual Basic .NET Visual Basic, originally called Visual Basic .NET (VB.NET), is a multi-paradigm, object-oriented programming language, implemented on .NET, Mono, and the .NET Framework. Microsoft launched VB.NET in 2002 as the successor to its original Visua ...

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offici ...

PHP PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group ...

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...

Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...

(when using NSArray, not a

row-major In computing, row-major order and column-major order are methods for storing multidimensional arrays in linear storage such as random access memory. The difference between the orders lies in which elements of an array are contiguous in memory. In ...

C-style array),

Swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIFT, ...

, and

Atlas Autocode Atlas Autocode (AA)Original scans)) is a programming language developed around 1965 at the University of Manchester. A variant of the language ALGOL, it was developed by Tony Brooker and Derrick Morris for the Atlas computer. The AA compiler was ...

are implemented as Iliffe vectors. Iliffe vectors were used to implement sparse multidimensional arrays in the OLAP product

Holos Holos was an influential OLAP (Online Analytical Processing) product of the 1990s. Developed by Holistic Systems in 1987, the product remained in use until around 2004. The core of the Holos Server was a business intelligence (BI) virtual mach ...

. Iliffe vectors are contrasted with

dope vector In computer programming, a dope vector is a data structure used to hold information about a data object, especially its memory layout. Purpose Dope vectors are most commonly used to describe arrays, which commonly store multiple instances of a pa ...

s in languages such as Fortran, which contain the stride factors and offset values for the subscripts in each dimension.

References

Further reading