Concurrency - Parallel Execution
Introduction
Where a sequential execution can be imagined as a single worker on an assembly line moving between tasks, a parallel process is more like a series of workers, each doing a specific task.
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Parallel does not mean always that your process will use another CPU. Two processes can run in parallel using only one CPU
Parallelism use is only going to increase because:
- CPU clock speeds are barely increasing (Moores law hits the roof),
- Multi-core processors are standard,
- and networks are getting faster.
Parallel execution is the ability to :
- divide a single operation through the hardware ressource
- apply multiple CPU and I/O resources to the execution of a single operation.
There are three architectures and approaches to increase performance through paralleled work over additional hardware:
- shared disk known also as shared memory or shared everything
See also: Parallel Programming - (Function|Operation)
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Implementation
mechanism by which a task can be run in parallel may be:
- time-sharing cooperative multitasking,
- fibers,
- threads,
- processes, using different hyperthreads,
- cores,
- CPUs,
- machines,
- etc.