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Python编程实现蚁群算法详解编程实现蚁群算法详解
主要介绍了Python编程实现蚁群算法详解,涉及蚂蚁算法的简介,主要原理及公式,以及Python中的实现代码,具有一定参考价值,需要的朋友可以了解下。
简介简介
蚁群算法(ant colony optimization, ACO),又称蚂蚁算法,是一种用来在图中寻找优化路径的机率型算法。它由Marco Dorigo于1992年在他的博士论文中提出,其灵感来源于蚂蚁在寻找食物过程中发现
路径的行为。蚁群算法是一种模拟进化算法,初步的研究表明该算法具有许多优良的性质。针对PID控制器参数优化设计问题,将蚁群算法设计的结果与遗传算法设计的结果进行了比较,数值仿真结果
表明,蚁群算法具有一种新的模拟进化优化方法的有效性和应用价值。
定义
各个蚂蚁在没有事先告诉他们食物在什么地方的前提下开始寻找食物。当一只找到食物以后,它会向环境释放一种挥发性分泌物pheromone (称为信息素,该物质随着时间的推移会逐渐挥发消失,信息素
浓度的大小表征路径的远近)来实现的,吸引其他的蚂蚁过来,这样越来越多的蚂蚁会找到食物。有些蚂蚁并没有像其它蚂蚁一样总重复同样的路,他们会另辟蹊径,如果另开辟的道路比原来的其他道路
更短,那么,渐渐地,更多的蚂蚁被吸引到这条较短的路上来。最后,经过一段时间运行,可能会出现一条最短的路径被大多数蚂蚁重复着。
解决的问题解决的问题
三维地形中,给出起点和重点,找到其最优路径。
作图源码:
from mpl_toolkits.mplot3d import proj3d
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
height3d = np.array([[2000,1400,800,650,500,750,1000,950,900,800,700,900,1100,1050,1000,1150,1300,1250,1200,1350,1500], [1100,900,700,625,550,825,1100,1150,1200,925,650,750,850,950,1050,1175,1300,1350,1400,1425,1450], [200,400,600,600,600,900,1200,1350,1500,1050,600,600,600,850,1100,1200,1300,1450,1600,1500,1400], [450,500,550,575,600,725,850,875,900,750,600,600,600,725,850,900,950,1150,1350,1400,1450], [700,600,500,550,600,550,500,400,300,450,600,600,600,600,600,600,600,850,1100,1300,1500], [500,525,550,575,600,575,550,450,350,475,600,650,700,650,600,600,600,725,850,1150,1450], [300,450,600,600,600,600,600,500,400,500,600,700,800,700,600,600,600,600,600,1000,1400], [550,525,500,550,600,875,1150,900,650,725,800,700,600,875,1150,1175,1200,975,750,875,1000], [800,600,400,500,600,1150,1700,1300,900,950,1000,700,400,1050,1700,1750,1800,1350,900,750,600], [650,600,550,625,700,1175,1650,1275,900,1100,1300,1275,1250,1475,1700,1525,1350,1200,1050,950,850], [500,600,700,750,800,1200,1600,1250,900,1250,1600,1850,2100,1900,1700,1300,900,1050,1200,1150,1100], [400,375,350,600,850,1200,1550,1250,950,1225,1500,1750,2000,1950,1900,1475,1050,975,900,1175,1450], [300,150,0,450,900,1200,1500,1250,1000,1200,1400,1650,1900,2000,2100,1650,1200,900,600,1200,1800], [600,575,550,750,950,1275,1600,1450,1300,1300,1300,1525,1750,1625,1500,1450,1400,1125,850,1200,1550], [900,1000,1100,1050,1000,1350,1700,1650,1600,1400,1200,1400,1600,1250,900,1250,1600,1350,1100,1200,1300], [750,850,950,900,850,1000,1150,1175,1200,1300,1400,1325,1250,1125,1000,1150,1300,1075,850,975,1100], [600,700,800,750,700,650,600,700,800,1200,1600,1250,900,1000,1100,1050,1000,800,600,750,900], [750,775,800,725,650,700,750,775,800,1000,1200,1025,850,975,1100,950,800,900,1000,1050,1100], [900,850,800,700,600,750,900,850,800,800,800,800,800,950,1100,850,600,1000,1400,1350,1300], [750,800,850,850,850,850,850,825,800,750,700,775,850,1000,1150,875,600,925,1250,1100,950], [600,750,900,1000,1100,950,800,800,800,700,600,750,900,1050,1200,900,600,850,1100,850,600]])
fig = figure()
ax = Axes3D(fig)
X = np.arange(21)
Y = np.arange(21)
X, Y = np.meshgrid(X, Y)
Z = -20*np.exp(-0.2*np.sqrt(np.sqrt(((X-10)**2+(Y-10)**2)/2)))+20+np.e-np.exp((np.cos(2*np.pi*X)+np.sin(2*np.pi*Y))/2)
ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap='cool')
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z')
ax.set_title('3D map')
point0 = [0,9,Z[0][9]]
point1 = [20,7,Z[20][7]]
ax.plot([point0[0]],[point0[1]],[point0[2]],'r',marker = u'o',markersize = 15)
ax.plot([point1[0]],[point1[1]],[point1[2]],'r',marker = u'o',markersize = 15)
x0,y0,_ = proj3d.proj_transform(point0[0],point0[1],point0[2], ax.get_proj())
x1,y1,_ = proj3d.proj_transform(point1[0],point1[1],point1[2], ax.get_proj())
label = pylab.annotate(
"start",
xy = (x0, y0), xytext = (-20, 20),
textcoords = 'offset points', ha = 'right', va = 'bottom',
bbox = dict(boxstyle = 'round,pad=0.5', fc = 'yellow', alpha = 1),
arrowprops = dict(arrowstyle = '->', connectionstyle = 'arc3,rad=0'),fontsize=15)
label2 = pylab.annotate(
"end",
xy = (x1, y1), xytext = (-20, 20),
textcoords = 'offset points', ha = 'right', va = 'bottom',
bbox = dict(boxstyle = 'round,pad=0.5', fc = 'yellow', alpha = 1),
arrowprops = dict(arrowstyle = '->', connectionstyle = 'arc3,rad=0'),fontsize=15)
def update_position(e):
x2, y2, _ = proj3d.proj_transform(point0[0],point0[1],point0[2],ax.get_proj())
label.xy = x2,y2
label.update_positions(fig.canvas.renderer)
x1,y1,_ = proj3d.proj_transform(point1[0],point1[1],point1[2],ax.get_proj())
label2.xy = x1,y1
label2.update_positions(fig.canvas.renderer)
fig.canvas.draw()
fig.canvas.mpl_connect('button_release_event', update_position)
基本原理基本原理
蚂蚁k根据各个城市间链接路径上的信息素浓度决定其下一个访问城市,设P
k
ij
(t)表示t时刻蚂蚁k从城市i转移到矩阵j的概率,其计算公式为
计算完城市间的转移概率后,采用与遗传算法中一样的轮盘赌方法选择下一个待访问的城市。
当所有的蚂蚁完成一次循环后,各个城市间链接路径上的信息素浓度需进行更新,计算公式为
















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