A programming model is an

execution model A programming language consists of a grammar/syntax plus an execution model. The execution model specifies the behavior of elements of the language. By applying the execution model, one can derive the behavior of a program that was written in term ...

coupled to an

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

or a particular pattern of code. In this style, there are actually two execution models in play: the execution model of the base

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

and the execution model of the programming model. An example is

Spark Spark commonly refers to: * Spark (fire), a small glowing particle or ember * Electric spark, a form of electrical discharge Spark may also refer to: Places * Spark Point, a rocky point in the South Shetland Islands People * Spark (surname) * ...

where Java is the base language, and Spark is the programming model. Execution may be based on what appear to be

library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...

calls. Other examples include the

POSIX Threads POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. Each flow of ...

library and Hadoop's

MapReduce MapReduce is a programming model and an associated implementation for processing and generating big data sets with a parallel, distributed algorithm on a cluster. A MapReduce program is composed of a ''map'' procedure, which performs filtering ...

. In both cases, the

of the programming model is different from that of the base language in which the code is written. For example, the

C programming language ''The C Programming Language'' (sometimes termed ''K&R'', after its authors' initials) is a computer programming book written by Brian Kernighan and Dennis Ritchie, the latter of whom originally designed and implemented the language, as well as ...

has no behavior in its execution model for input/output or thread behavior. But such behavior can be invoked from C syntax, by making what appears to be a call to a normal C library. What distinguishes a programming model from a normal library is that the behavior of the call cannot be understood in terms of the language the program is written in. For example, the behavior of calls to the POSIX thread library cannot be understood in terms of the C language. The reason is that the call invokes an execution model that is different from the execution model of the language. This invocation of an outside execution model is the defining characteristic of a programming ''model'', in contrast to a programming ''language''. In

parallel computing Parallel computing is a type of computation in which many calculations or processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different fo ...

, the execution model often must expose features of the hardware in order to achieve high performance. The large amount of variation in parallel hardware causes a concurrent need for a similarly large number of parallel execution models. It is impractical to make a new language for each execution model, hence it is a common practice to invoke the behaviors of the parallel execution model via an API. So, most of the programming effort is done via parallel programming models rather than parallel languages. Unfortunately, the terminology around such programming models tends to focus on the details of the hardware that inspired the execution model, and in that insular world the mistaken belief is formed that a programming model is only for the case when an execution model is closely matched to hardware features.

References

{{Reflist Computer programming