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Adding Multitasking Capability to Applications Using Multiprocessing Services

   

Sequential Tasks

For some applications, you may want to create several different tasks, each of which performs a different function. Some of these tasks might be able to operate in parallel, in which case you can adapt the "divide and conquer" model to perform the work. However, sometimes the output of one task is needed as the input of another. For example a sound effects application may need to process several different effects in sequence (reverb, limiting, flanging, and so on). Each task can process a particular effect, and the output of one task would feed into the input of the next. In this case, a sequential or "pipeline" architecture is appropriate.

Note that a sequential task architecture benefits from multiple processors only if several of the tasks can operate at the same time; that is, new data must be entering the pipeline while other tasks are processing data further down the line. It is harder with this architecture than with parallel task architectures to ensure that all processors are being used at all times, so you should add parallel tasks to individual stages of the pipeline whenever possible.

As shown in Figure 2-5 , the sequential task architecture requires a single input buffer and a single output buffer for the pipeline, and intermediate buffers between sequential tasks.

Figure 2-5   Sequential tasks