Java Performance Tuning

Threaded Problem-Solving Strategies

There are many techniques that reduce the time taken to solve intensive problems by using multiple threads to farm out parts of the problem. Here are a few of the strategies:

• Start multiple threads running to solve the whole of a particular problem, each starting from a different point in the solution space. The first to finish is the winner. This technique has, for instance, been used to speed up a graph-coloring problem. The specific strategy followed^[74] was to run several problem solvers at the same time, one at a higher priority than the others (the main thread). Normally the main thread would win, but on occasion, one of the background threads was lucky due to its starting point and finished quickly. By stopping the main thread if it looked to be far behind in the solution, the problem was solved in one-tenth of the time, on average, compared to the time taken when the main thread was not terminated. This improvement was in spite of the fact that this was a single-processor machine. The improvement comes about because the problem can be solved much quicker from some starting points than from others. There would be similar improvements if you also used several different problem-solving strategies in the various threads, where some of the strategies are sometimes quicker than others.

• In the same article, a variation of this strategy was applied to network connections for bypassing congestion. By opening multiple connections to download the ...