Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, implicit parallelism is a characteristic of a programming language that allows a compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
or interpreter to automatically exploit the parallelism
Parallel computing
Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently . There are several different forms of parallel computing: bit-level,...
inherent to the computations expressed by some of the language's constructs. A pure implicitly parallel language does not need special directives, operators or functions to enable parallel execution.
Programming languages with implicit parallelism include Axum
Axum (programming language)
Axum is a domain specific concurrent programming language, based on the Actor model, being developed by Microsoft...
High Performance Fortran is an extension of Fortran 90 with constructs that support parallel computing, published by the High Performance Fortran Forum . The HPFF was convened and chaired by Ken Kennedy of Rice University...
Id is a general-purpose parallel programming language, developed by Arvind and Nikhil, at MIT, in the late 1970 and throughout the 1980s. The major subset of Id is a purely functional programming language with non-strict semantics...
LabVIEW is a system design platform and development environment for a visual programming language from National Instruments. LabVIEW provides engineers and scientists with the tools needed to create and deploy measurement and control systems.The graphical language is named "G"...
MATLAB is a numerical computing environment and fourth-generation programming language. Developed by MathWorks, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages,...
NESL is a parallel programming language developed at Carnegie Mellon by the SCandAL project and released in 1993. It integrates various ideas from parallel algorithms, and functional programming and array programming languages....
SAC is a strict purely functional programming language which design is focused on the needs of numerical applications. Emphasis is laid on efficient support for array processing. Efficiency concerns are essentially twofold...
SISAL is a general-purpose single assignment functional programming language with strict semantics, implicit parallelism, and efficient array handling. SISAL outputs a dataflow graph in Intermediary Form 1...
ZPL is an array programming language designed to replace C and C++ programming languages in engineering and scientific applications. Because its design goal was to obtain cross-platform high performance, ZPL programs run fast on both sequential and parallel computers...
, and pH
.
Example
If a particular problem involves performing the same operation on a group of numbers (such as taking the sine
Sine
In mathematics, the sine function is a function of an angle. In a right triangle, sine gives the ratio of the length of the side opposite to an angle to the length of the hypotenuse.Sine is usually listed first amongst the trigonometric functions....
The logarithm of a number is the exponent by which another fixed value, the base, has to be raised to produce that number. For example, the logarithm of 1000 to base 10 is 3, because 1000 is 10 to the power 3: More generally, if x = by, then y is the logarithm of x to base b, and is written...
of each in turn), a language that provides implicit parallelism might allow the programmer to write the instruction thus:
The compiler or interpreter can calculate the sine of each element independently, spreading the effort across multiple processors if available.
Advantages
A programmer that writes implicitly parallel code does not need to worry about task division or process communication, focusing instead in the problem that his or her program is intended to solve. Implicit parallelism generally facilitates the design of parallel programs and therefore results in a substantial improvement of programmer productivity.
Disadvantages
Languages with implicit parallelism reduce the control that the programmer has over the parallel execution of the program, resulting sometimes in less-than-optimal parallel efficiency. The makers of the Oz programming language also note that their early experiments with implicit parallelism showed that implicit parallelism made debugging difficult and object models unnecessarily awkward.
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