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Parallel programming models are closely related to models of computation. A model of parallel computation is an abstraction used to analyze the cost of computational processes, but it does not necessarily need to be practical, in that it can be implemented efficiently in hardware and/or software. A programming model, in contrast, does ...
Bit-level parallelism is a form of parallel computing based on increasing processor word size.Increasing the word size reduces the number of instructions the processor must execute in order to perform an operation on variables whose sizes are greater than the length of the word.
In parallel computing, granularity (or grain size) of a task is a measure of the amount of work (or computation) which is performed by that task. [1] Another definition of granularity takes into account the communication overhead between multiple processors or processing elements. It defines granularity as the ratio of computation time to ...
One concept used in programming parallel programs is the future concept, where one part of a program promises to deliver a required datum to another part of a program at some future time. Efforts to standardize parallel programming include an open standard called OpenHMPP for hybrid multi-core parallel programming.
A program running on a parallel computer may utilize different numbers of processors at different times. For each time period, the number of processors used to execute a program is defined as the degree of parallelism. The plot of the DOP as a function of time for a given program is called the parallelism profile. [2]
Parallelism executes tasks independently on multiple CPU cores, while concurrency manages multiple tasks on one or more cores, switching between threads or time-slicing without completing each one. Programs may exhibit parallelism only, concurrency only, both parallelism and concurrency, neither. [6] Parallelism vs concurrency
Atanasoff–Berry computer, the first computer with parallel processing [1] Instruction-level parallelism (ILP) is the parallel or simultaneous execution of a sequence of instructions in a computer program. More specifically, ILP refers to the average number of instructions run per step of this parallel execution. [2]: 5
Designs of parallel processors use special buses like crossbar so that the communication overhead will be small but it is the parallel algorithm that decides the volume of the traffic. If the communication overhead of additional processors outweighs the benefit of adding another processor, one encounters parallel slowdown .