NSGA2快速非支配排序实现-python
1 import numpy as np 2 3 4 def compare(p1, p2): 5 # return 0同层 1 p1支配p2 6 # 每个维度越小越优秀 7 # 计D次 8 D = len(p1) 9 p1_dominate_p2 = True # p1 更小 10 p2_dominate_p1 = True 11 for i in range(D): 12 if p1[i] > p2[i]: 13 p1_dominate_p2 = False 14 if p1[i] < p2[i]: 15 p2_dominate_p1 = False 16 17 if p1_dominate_p2 == p2_dominate_p1: 18 return 0 19 return 1 if p1_dominate_p2 else -1 20 21 22 def fast_non_dominated_sort(P): 23 # 成员编号为 0 ~ P_size-1 24 P_size = len(P) 25 # 被支配数 26 n = np.full(shape=P_size, fill_value=0) 27 # 支配的成员 28 S = [] 29 # 每层包含的成员编号们 30 f = [] # 0 开始 31 # 所处等级 32 rank = np.full(shape=P_size, fill_value=-1) 33 34 f_0 = [] 35 for p in range(P_size): 36 n_p = 0 37 S_p = [] 38 for q in range(P_size): 39 if p == q: 40 continue 41 cmp = compare(P[p], P[q]) 42 if cmp == 1: 43 S_p.append(q) 44 elif cmp == -1: # 被支配 45 n_p += 1 46 S.append(S_p) 47 n[p] = n_p 48 if n_p == 0: 49 rank[p] = 0 50 f_0.append(p) 51 52 f.append(f_0) # 这时候f[0]必存在 53 54 i = 0 55 while len(f[i]) != 0: # 可能还有i+1层 56 Q = [] 57 for p in f[i]: # i层中每个个体 58 for q in S[p]: # 被p支配的个体 59 n[q] -= 1 60 if n[q] == 0: 61 rank[q] = i + 1 62 Q.append(q) 63 i += 1 64 f.append(Q) 65 return rank, f 66 67 68 import matplotlib.pyplot as plt 69 70 if __name__ == '__main__': 71 P = np.random.random(size=(200, 2)) 72 rank, f = fast_non_dominated_sort(P) 73 f.pop() 74 # print(rank) 75 # print(f) 76 77 # 绘图 78 for t in f: 79 # 每level 80 x = P[t][:, 0] 81 y = P[t][:, 1] 82 plt.scatter(x, y, s=15) # s 点的大小 c 点的颜色 alpha 透明度 83 84 plt.show()
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