plot_operators.py

# Generates a plot showing the distributions of six real-valued operators.
import matplotlib.pyplot as plt

from platypus import (PCX, PM, SBX, SPX, UM, UNDX, DifferentialEvolution,
                      GAOperator, Problem, Real, Solution)

problem = Problem(2, 0)
problem.types[:] = Real(-1, 1)

solution1 = Solution(problem)
solution1.variables[:] = [-0.25, -0.25]

solution2 = Solution(problem)
solution2.variables[:] = [0.25, -0.25]

solution3 = Solution(problem)
solution3.variables[:] = [0.0, 0.25]

def generate(variator, parents):
    result = []

    while len(result) < 10000:
        result.extend(variator.evolve(parents))

    return to_points(result)

def to_points(solutions):
    return [s.variables[0] for s in solutions], [s.variables[1] for s in solutions]

fig, axarr = plt.subplots(2, 3)
options = {"s": 0.1, "alpha": 0.5}
parent_options = {"s": 25, "color": "b"}

axarr[0, 0].scatter(*generate(GAOperator(SBX(1.0, 20.0), PM(0.5, 250.0)), [solution1, solution3]), **options)
axarr[0, 0].scatter(*to_points([solution1, solution3]), **parent_options)
axarr[0, 0].set_title("SBX")

axarr[0, 1].scatter(*generate(GAOperator(DifferentialEvolution(1.0, 1.0), PM(0.5, 100.0)), [solution3, solution2, solution1, solution3]), **options)
axarr[0, 1].scatter(*to_points([solution3, solution2, solution1, solution3]), **parent_options)
axarr[0, 1].set_title("DE")

axarr[0, 2].scatter(*generate(UM(0.5), [solution1]), **options)
axarr[0, 2].scatter(*to_points([solution1]), **parent_options)
axarr[0, 2].set_title("UM")

axarr[1, 0].scatter(*generate(PCX(3, 2), [solution1, solution2, solution3]), **options)
axarr[1, 0].scatter(*to_points([solution1, solution2, solution3]), **parent_options)
axarr[1, 0].set_title("PCX")

axarr[1, 1].scatter(*generate(UNDX(3, 2), [solution1, solution2, solution3]), **options)
axarr[1, 1].scatter(*to_points([solution1, solution2, solution3]), **parent_options)
axarr[1, 1].set_title("UNDX")

axarr[1, 2].scatter(*generate(SPX(3, 2), [solution1, solution2, solution3]), **options)
axarr[1, 2].scatter(*to_points([solution1, solution2, solution3]), **parent_options)
axarr[1, 2].set_title("SPX")

# add arrow annotations to DE
axarr[0, 1].annotate("",
                     xy=solution3.variables, xycoords='data',
                     xytext=solution1.variables, textcoords='data',
                     arrowprops=dict(arrowstyle="fancy",
                                     connectionstyle="arc3",
                                     color="0.75"))
axarr[0, 1].annotate("",
                     xy=[solution2.variables[i] + (solution3.variables[i] - solution1.variables[i]) for i in range(2)], xycoords='data',
                     xytext=solution2.variables, textcoords='data',
                     arrowprops=dict(arrowstyle="fancy",
                                     connectionstyle="arc3",
                                     color="0.75"))

for i in range(1):
    for j in range(3):
        axarr[i, j].set_xticklabels([])
        axarr[i, j].set_yticklabels([])
        axarr[i, j].autoscale(tight=True)

plt.show()