TABLE OF CONTENTS As discussed in previous chapters, parallel programming uses threads to enable multiple operations to proceed simultaneously. The entire concept of parallel programming centers on the design, development, and deployment of threads within an application and the coordination between threads and their respective operations. This chapter examines how to break up programming tasks into chunks that are suitable for threading. It then applies these techniques to the apparently serial problem of error diffusion.
Developers who are unacquainted with parallel programming generally feel comfortable with traditional programming models, such as object-oriented programming (OOP). In this case, a program begins at a defined point, such as the main() function, and works through a series of tasks in succession. If the program relies on user interaction, the main processing instrument is a loop in which user events are handled. From each allowed event a button click, for example, the program performs an established sequence of actions that ultimately ends with a wait for the next user action.
When designing such programs, developers enjoy a relatively simple programming world because only one thing is happening at any given moment. If program tasks must be scheduled in a specific way, it's because the developer imposes a certain order on the activities. At any point in the process, one step generally flows into the next, leading up to a predictable conclusion, based on predetermined parameters.
To move from this linear model to a parallel programming model, designers must rethink the idea of process flow.
