说明：   PSOpt is a program to demonstrate the optimization process of particle swarm optimization. A two-dimensional objective function is visualized by levels of grey: the lighter the color, the higher the function value. The particles are shown as red circles, their trajectory as red lines. The global memory (best point found up to now by the whole swarm) is shown as a blue cross-hair, the local memory (best points found by each of the particles) as small blue crosses. To run the program, first choose one of the example functions, then create a particle swarm, and finally start the optimization.