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This article lists concurrent and parallel programming languages, categorizing them by a defining paradigm.Concurrent and parallel programming languages involve multiple timelines.
Concurrent computations may be executed in parallel, [3] [6] for example, by assigning each process to a separate processor or processor core, or distributing a computation across a network. The exact timing of when tasks in a concurrent system are executed depends on the scheduling , and tasks need not always be executed concurrently.
The pseudo-code for multiplication calculates the dot product of two matrices A, B and stores the result into the output matrix C. If the following programs were executed sequentially, the time taken to calculate the result would be of the O ( n 3 ) {\displaystyle O(n^{3})} (assuming row lengths and column lengths of both matrices are n) and O ...
The goal of the program is to do some net total task ("A+B"). If we write the code as above and launch it on a 2-processor system, then the runtime environment will execute it as follows. In an SPMD (single program, multiple data) system, both CPUs will execute the code. In a parallel environment, both will have access to the same data.
A skilled parallel programmer may take advantage of explicit parallelism to produce efficient code for a given target computation environment. However, programming with explicit parallelism is often difficult, especially for non-computing specialists, because of the extra work and skill involved in developing it.
This snippet of Go code performs similarly to the XC code. First the channel c is created, then a goroutine is spawned which sends 42 through the channel. When the number is put in the channel x is set to 42. Go allows channels to buffer contents, as well as non blocking receiving through the use of a select block. [2]
1: function Dep(a, b) 2: c := a * b 3: d := 3 * c 4: end function In this example, instruction 3 cannot be executed before (or even in parallel with) instruction 2, because instruction 3 uses a result from instruction 2. It violates condition 1, and thus introduces a flow dependency.
Futures can easily be implemented in channels: a future is a one-element channel, and a promise is a process that sends to the channel, fulfilling the future. [104] [105] This allows futures to be implemented in concurrent programming languages with support for channels, such as CSP and Go. The resulting futures are explicit, as they must be ...