1. Why "convection"? A simplified demonstration.

Lines moving up demonstrate selective pressure
in subpopulations (tournament, roulette, or other).

Vertical axis is fitness (top=best).

Color boxes are subpopulations (4).
For simplicity, their fitness ranges are fixed in this animation.

Green circles are individuals (5).
Moving up = improved children.
Falling down = children broken by mutations/crossovers.

In reality, parent individuals do not "disappear", and fitness ranges of subpopulations
adapt to the full range of fitness values of all existing individuals.

Read about details here.

2. Examples of real optimization problems.

In visualizations below, vertical gray bars are subpopulations. Dark circles are individuals (solutions). Dark reddish rectangles in gray bars indicate fitness ranges assigned to each subpopulation by the "equal width" approach.

The goal was to maximize fitness. The poorest individuals have a zero fitness. Negative selection is random, so sometimes we lose good individuals.

You will see two progress bars below each animation. The top progress bar shows time (generations) between merge-and-divide (or migration) events (there is a counter for these events). The bottom bar indicates the progress of the entire evolutionary process.

Read about details here.

2.1. Easy problem (the Rastrigin benchmark).

2.2. Difficult problem (3D design).

Click to see: Framsticks – maximization of the vertical position of the center of mass.