<parallel> (Or "multiprocessing") The simultaneous use of more than one computer to solve a problem. There are many different kinds of parallel computer (or "parallel processor"). They are distinguished by the kind of interconnection between processors (known as "processing elements" or PEs) and between processors and memory. {Flynn's taxonomy} also classifies parallel (and serial) computers according to whether all processors execute the same instructions at the same time ("{single instruction/multiple data}" - SIMD) or each processor executes different instructions ("multiple instruction/multiple data" - MIMD). The processors may either communicate in order to be able to cooperate in solving a problem or they may run completely independently, possibly under the control of another processor which distributes work to the others and collects results from them (a "processor farm"). The difficulty of cooperative problem solving is aptly demonstrated by the following dubious reasoning: If it takes one man one minute to dig a post-hole then sixty men can dig it in one second. Amdahl's Law states this more formally. Processors communicate via some kind of network or bus or a combination of both. Memory may be either shared memory (all processors have equal access to all memory) or private (each processor has its own memory - "distributed memory") or a combination of both. Many different software systems have been designed for programming parallel computers, both at the operating system and programming language level. These systems must provide mechanisms for partitioning the overall problem into separate tasks and allocating tasks to processors. Such mechanisms may provide either implicit parallelism - the system (the compiler or some other program) partitions the problem and allocates tasks to processors automatically or {explicit parallelism} where the programmer must annotate his program to show how it is to be partitioned. It is also usual to provide synchronisation primitives such as semaphores and monitors to allow processes to share resources without conflict. Load balancing attempts to keep all processors busy by allocating new tasks, or by moving existing tasks between processors, according to some algorithm. Communication between tasks may be either via shared memory or message passing. Either may be implemented in terms of the other and in fact, at the lowest level, shared memory uses message passing since the address and data signals which flow between processor and memory may be considered as messages. The terms "parallel processing" and "multiprocessing" imply multiple processors working on one task whereas "{concurrent processing}" and "multitasking" imply a single processor sharing its time between several tasks. See also cellular automaton,symmetric multi-processing. Usenet newsgroup: news:comp.parallel. Institutions (http://ccsf.caltech.edu/other_sites.html), {parallel processingscandal/research-groups.html">research groups (http://cs.cmu.edu/parallel processingscandal/research-groups.html)}. (2004-11-07)

<parallel> A computer with more than one {central processing unit}, used for parallel processing. (1996-04-23)

parallel processing

parallel processor

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.

In psychology, parallel processing is the ability of the brain to simultaneously process incoming stimuli of differing quality. Parallel processing is associated with the visual system in that the brain divides what it sees into four components: color, motion, shape, and depth.

Parallel multidimensional digital signal processing (mD-DSP) is defined as the application of parallel programming and multiprocessing to digital signal processing techniques to process digital signals that have more than a single dimension. The use of mD-DSP is fundamental to many application areas such as digital image and videoKeimel, Christian, Martin Rothbucher, Hao Shen, and Klaus Diepold.

Parallel Processing Letters is a journal published by World Scientific since 1991. It covers the field of parallel processing, including topics such as design and analysis of parallel and distributed algorithms, parallel programming languages and parallel architectures and VLSI circuits.