遗传算法解决TSP问题 Python实现【160行以内代码】
简述
之前通过遗传算法（Genetic Algorithm ）+C++实现解决TSP问题 写了一些基本的原理。并且给出了C++版本代码。
相比于近300行的C++程序，Python只用了160行就解决了 可以说是非常方便了~
基于之前的C++版本的Python版本代码
import numpy as np
import random
def read_data(file='data.txt'):
with open(file, 'r') as f:
N = int(f.readline().replace('\n', ''))
Mat = [0] * 10
for i in range(N):
Mat[i] = list(map(int, f.readline().replace('\n', '').split(' ')))
return N, Mat
def calpathValue(path):
global Mat
temp = Mat[0][path[0]]
for i in range(len(path) - 1):
temp += Mat[path[i]][path[i + 1]]
temp += Mat[path[-1]][0]
return temp
def initial():
global N
init = list(range(1, N, 1))
pack = [0] * LEN
packValue = [0] * LEN
for i in range(LEN):
random.shuffle(init)
data = init
pack[i] = data.copy()
packValue[i] = calpathValue(pack[i])
indexes = np.argsort(packValue)
pack = np.array(pack)[indexes]
packValue = np.sort(packValue)
return packValue, pack
# i: pack
def preserve(i):
global tempPack, tempPackValue, pack, packValue, tempIndex
tempPackValue[tempIndex] = packValue[i]
tempPack[tempIndex] = pack[i].copy()
tempIndex += 1
def select():
global N, pack, tempPack, tempPackValue, tempIndex, LEN, packValue
tpk = tempPack[:tempIndex]
tpkv = tempPackValue[:tempIndex]
indexes = np.argsort(tpkv)
tpk = np.array(tpk)[indexes]
tpkv = np.sort(tpkv)
pack = tpk[:LEN]
packValue = tpkv[:LEN]
def crossover(i, j):
global N, pack, tempPack, tempPackValue, tempIndex
times = random.randint(1, N - 2)
indexes = [0] * times
for t in range(times):
if t == 0:
indexes[t] = random.randint(0, N - times - 1)
else:
indexes[t] = random.randint(indexes[t - 1] + 1, N - times + t - 1)
tempPack[tempIndex] = pack[i].copy()
pack_j_reindex = pack[j].copy()[indexes]
count = 0
for v in range(N - 1):
if count >= times: break
if tempPack[tempIndex][v] in pack_j_reindex:
tempPack[tempIndex][v] = pack_j_reindex[count]
count += 1
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
tempPack[tempIndex] = pack[j].copy()
pack_i_reindex = pack[i].copy()[indexes]
count = 0
for v in range(N - 1):
if count >= times: break
if tempPack[tempIndex][v] in pack_i_reindex:
tempPack[tempIndex][v] = pack_i_reindex[count]
count += 1
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
def mutation(i):
global N, pack, tempPack, tempPackValue, tempIndex
times = random.randint(1, N - 2)
indexes = [0] * times
for t in range(times):
if t == 0:
indexes[t] = random.randint(0, N - times - 1)
else:
indexes[t] = random.randint(indexes[t - 1] + 1, N - times + t - 1)
origin_indexes = indexes.copy()
random.shuffle(indexes)
tempPack[tempIndex] = pack[i].copy()
for t in range(times):
tempPack[tempIndex][indexes[t]] = pack[i][origin_indexes[t]]
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
if __name__ == '__main__':
N, Mat = read_data()
LEN = 25
pc, pm = 0.7, 0.97
NOTMORETHANstayINGV = 10
packValue, pack = initial()
tempLEN = LEN * LEN
tempPack = [[0] * N] * tempLEN
tempPackValue = [0] * tempLEN
tempIndex = 0
global_Value = packValue[0]
stayinGV = 0
while True:
tempIndex = 0
for i in range(LEN):
preserve(i)
if random.random() < pm:
mutation(i)
if i == LEN - 1: break
for j in range(i + 1, LEN):
if tempIndex >= tempLEN: break
if random.random() < pc:
crossover(i, j)
select()
if packValue[0] < global_Value:
global_Value = packValue[0]
stayinGV = 0
elif packValue[0] == global_Value:
stayinGV += 1
else:
print("Something wrong")
break
if stayinGV == NOTMORETHANstayINGV:
break
print(global_Value)
print(0, end='-->')
for i in pack[0]:
print(i, end='-->')
- 所用的数据：
- 表示是的10个点之间的距离矩阵
10
0 58 82 89 17 50 26 48 70 19
58 0 74 46 70 2 70 49 87 60
82 74 0 58 76 98 37 97 34 67
89 46 58 0 15 17 28 69 46 79
17 70 76 15 0 98 60 69 97 89
50 2 98 17 98 0 81 14 43 47
26 70 37 28 60 81 0 43 73 56
48 49 97 69 69 14 43 0 39 0
70 87 34 46 97 43 73 39 0 53
19 60 67 79 89 47 56 0 53 0
随机生成数据并展示动图
- 黑色的点是起点。
- 我在知乎上看到类似的图，就试着改了下自己的代码也实现了这个效果。生成gif是基于我之前写的代码
import numpy as np
import random
import matplotlib.pyplot as plt
import os
import shutil
import imageio
def create_data(N, xu=10, yu=10, xd=-10, yd=-10):
fx = lambda: random.random() * (xu - xd) + xd
fy = lambda: random.random() * (yu - yd) + yd
calDistance = lambda x, y: np.sqrt((x[0] - y[0]) ** 2 + (x[1] - y[1]) ** 2)
points = [(0, 0)] * N
for i in range(N):
points[i] = (fx(), fy())
Mat = np.zeros((N, N))
for i in range(N):
for j in range(i + 1, N):
dv = calDistance(points[i], points[j])
Mat[i][j], Mat[j][i] = dv, dv
return points, Mat
def calpathValue(path):
global Mat
temp = Mat[0][path[0]]
for i in range(len(path) - 1):
temp += Mat[path[i]][path[i + 1]]
temp += Mat[path[-1]][0]
return temp
def initial():
global N
init = list(range(1, N, 1))
pack = [0] * LEN
packValue = [0] * LEN
for i in range(LEN):
random.shuffle(init)
data = init
pack[i] = data.copy()
packValue[i] = calpathValue(pack[i])
indexes = np.argsort(packValue)
pack = np.array(pack)[indexes]
packValue = np.sort(packValue)
return packValue, pack
# i: pack
def preserve(i):
global tempPack, tempPackValue, pack, packValue, tempIndex
tempPackValue[tempIndex] = packValue[i]
tempPack[tempIndex] = pack[i].copy()
tempIndex += 1
def select():
global N, pack, tempPack, tempPackValue, tempIndex, LEN, packValue
tpk = tempPack[:tempIndex]
tpkv = tempPackValue[:tempIndex]
indexes = np.argsort(tpkv)
tpk = np.array(tpk)[indexes]
tpkv = np.sort(tpkv)
pack = tpk[:LEN]
packValue = tpkv[:LEN]
def crossover(i, j):
global N, pack, tempPack, tempPackValue, tempIndex
times = random.randint(1, N - 2)
indexes = [0] * times
for t in range(times):
if t == 0:
indexes[t] = random.randint(0, N - times - 1)
else:
indexes[t] = random.randint(indexes[t - 1] + 1, N - times + t - 1)
tempPack[tempIndex] = pack[i].copy()
pack_j_reindex = pack[j].copy()[indexes]
count = 0
for v in range(N - 1):
if count >= times: break
if tempPack[tempIndex][v] in pack_j_reindex:
tempPack[tempIndex][v] = pack_j_reindex[count]
count += 1
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
tempPack[tempIndex] = pack[j].copy()
pack_i_reindex = pack[i].copy()[indexes]
count = 0
for v in range(N - 1):
if count >= times: break
if tempPack[tempIndex][v] in pack_i_reindex:
tempPack[tempIndex][v] = pack_i_reindex[count]
count += 1
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
def mutation(i):
global N, pack, tempPack, tempPackValue, tempIndex
times = random.randint(1, N - 2)
indexes = [0] * times
for t in range(times):
if t == 0:
indexes[t] = random.randint(0, N - times - 1)
else:
indexes[t] = random.randint(indexes[t - 1] + 1, N - times + t - 1)
origin_indexes = indexes.copy()
random.shuffle(indexes)
tempPack[tempIndex] = pack[i].copy()
for t in range(times):
tempPack[tempIndex][indexes[t]] = pack[i][origin_indexes[t]]
tempPackValue[tempIndex] = calpathValue(tempPack[tempIndex])
tempIndex += 1
def draw(path, pv):
global points, N, TIMESIT, PNGFILE, PNGLIST
plt.cla()
plt.title('cross=%.4f' % pv)
xs = [p[0] for p in points]
ys = [p[1] for p in points]
plt.scatter(xs, ys, color='b')
xs = np.array(xs)
ys = np.array(ys)
plt.plot(xs[[0, path[0]]], ys[[0, path[0]]], color='r')
for i in range(N - 2):
plt.plot(xs[[path[i], path[i + 1]]], ys[[path[i], path[i + 1]]], color='r')
plt.plot(xs[[path[N - 2], 0]], ys[[path[N - 2], 0]], color='r')
plt.scatter(xs[0], ys[0], color='k', linewidth=10)
plt.savefig('%s/%d.png' % (PNGFILE, TIMESIT))
PNGLIST.append('%s/%d.png' % (PNGFILE, TIMESIT))
TIMESIT += 1
if __name__ == '__main__':
# N, Mat = read_data()
TIMESIT = 0
PNGFILE = './png/'
PNGLIST = []
if not os.path.exists(PNGFILE):
os.mkdir(PNGFILE)
else:
shutil.rmtree(PNGFILE)
os.mkdir(PNGFILE)
N = 20
points, Mat = create_data(N)
LEN = 40
pc, pm = 0.7, 0.97
NOTMORETHANstayINGV = 30
packValue, pack = initial()
tempLEN = LEN * LEN
tempPack = [[0] * N] * tempLEN
tempPackValue = [0] * tempLEN
tempIndex = 0
global_Value = packValue[0]
draw(pack[0], global_Value)
stayinGV = 0
while True:
tempIndex = 0
for i in range(LEN):
preserve(i)
if random.random() < pm:
mutation(i)
if i == LEN - 1: break
for j in range(i + 1, LEN):
if tempIndex >= tempLEN: break
if random.random() < pc:
crossover(i, j)
select()
if packValue[0] < global_Value:
global_Value = packValue[0]
draw(pack[0], global_Value)
stayinGV = 0
elif packValue[0] == global_Value:
stayinGV += 1
else:
print("Something wrong")
break
if stayinGV == NOTMORETHANstayINGV:
break
print(global_Value)
print(0, end='-->')
for i in pack[0]:
print(i, end='-->')
generated_images = []
for png_path in PNGLIST:
generated_images.append(imageio.imread(png_path))
shutil.rmtree(PNGFILE) # 可删掉
generated_images = generated_images + [generated_images[-1]] * 5
imageio.mimsave('TSP-GA.gif', generated_images, 'GIF', duration=0.5)