Results for the Rosenbrock function using the PSO algorithm: the distribution of the parameter values after 819 function calls (χ² = 2.31  ×  10^-5) is indicated by green-yellow points. The sequence of iterations is color-coded (color bar on the lower right). Early points are denoted in dark green, points toward the end of the iteration are light yellow. The red dot denotes the global minimum of the Rosenbrock function. (The clustering of the function calls right above the global minimum is caused by the very flat gradient of the Rosenbrock function in this area.)