我想將 GA 的作業 matlab 代碼移植到 python。在 matlab 中，我在 10% 的裕度（足以快速瀏覽）內達到最佳狀態，人口為 10 和 10K 代。現在我嘗試將此代碼移植到 python 并得到奇怪的行為，即解決方案似乎停留在特定（但隨機）值上，有時離最佳值太遠了。
呼叫example1p6A(10000,10,0,0)使用提供的 matlab 代碼導致
x*=
1.9707
3.0169
f(x*)=
0.9959
有一些差異，因為它使用亂數但總是接近上述結果。當你有一個開放的數字時，它會在平均 0.8 左右擺動的情況下繪制 gererations 的演變。
但是，當我在移植的 python 代碼中呼叫相同的函式時，我得到了不同的結果，例如
x* = [1.89979667 3.39332522]
f_max = 0.5499656257996797
到處都是，有時很遠。讓我感到奇怪的是，與 matlab 繪圖形成鮮明對比的是，經過幾代后，繪制的最小值、最大值和中位數似乎都相同。
我花了一整天的時間試圖找到我的錯誤，但沒有成功。
我所知道的事情是：
- 向量的索引在 python 中從 0->N-1 開始，而不是在 matlab 中從 1->N 開始
- 一個 for 回圈被明確地限制了，因為我對不均勻的人口有一個錯誤。Matlab 似乎隱含地做到了這一點。
- 相當于
size()python中的matlab是shape()
現在我不知道可能是什么問題。我將提供兩個圖，以便您可以快速查看我的結果。
function example1p6A(NG,Np,rf,pf)
% example1p6A is a function to generate example 1.6A in
% Power Magnetic Devices: A Multi-Ojective Design Approach
% by S.D. Sudhoff
%
% Call:
% example1p6A(NG,Np,rf,pf)
%
% Input:
% NG = number of generations
% Np = size of population
% rf = report flag (set to 1 to write report)
% pf = plot flag (set to 1 to plot results)
%
% Output:
% All output is textual or graphical
%
% Internal:
% GA = structure of genetic algorithm parameters
% GA.Ng = number of genes
% GA.Np = number in population
% GA.NG = number of generations
% GA.pc = probability of crossover
% GA.pm = probabiligy of gene mutation
% GA.xmn = vector of minimum values for unnormalized genes
% GA.xmx = vector of maximum values for unnormalized genes
% g = generation counter
% P = the population (number of genes by number of individuals)
% PC = copy of the population
% x = uncoded gene values of population
% f = fitness of population
% M = mutated populatin
% fmn = mean fitness of population
% fmx = maximum fitness of population
% fmd = median fitness of population
%
% Version/Date:
% May 7, 2013
%
% Written by:
% S.D. Sudhoff
% Purdue University
% Electrical Engineering Building
% 465 Northwestern Avenue
% West Lafayette, IN 47907-2035
% [email protected]
% 765-497-7648
GA.Ng=2; % number of genes
GA.Np=Np; % size of population
GA.NG=NG; % number of generations
GA.pc=0.5; % probability of crossover
GA.alpha=0.5; % blend ratio for crossover
GA.pm=0.1; % probability of a gene being mutated
GA.xmn=[0 0]; % vector of minimum values for unnormalized genes
GA.xmx=[5 5]; % vector of maximum values for unnormalized genes
% initialize the population
P=rand(GA.Ng,GA.Np);
% loop over the generation
for g=1:GA.NG
% make copy of current population
PC=P;
% find the parameter values for each member of the population
x=decode(P,GA);
% find the fitness
f=fitness(x);
if (g<GA.NG)
% find the mating pool
M=select(P,f,GA);
% create the next generation
P=children(M,GA);
end
fmn(g)=mean(f);
fmx(g)=max(f);
fmd(g)=median(f);
% plot
if pf
figure(1)
s=mod(g-1,9) 1;
symbol={'o','x',' ','*','s','d','v','p','h'};
plot(x(1,:),x(2,:),symbol{s},'Color',[0.8 0.8 0.8]*(1-g/GA.NG));
hold on;
end
% text report
if rf
disp(['Generation = ' num2str(g)]);
disp('P=');
disp(PC)
disp('x=');
disp(x)
disp('f=');
disp(f)
if (g<GA.NG)
disp('M=');
disp(M);
end
disp(['mean f = ' num2str(fmn(g))]);
disp(['max f = ' num2str(fmx(g))]);
disp(['median f = ' num2str(fmd(g))]);
end
end % generation loop
% finish plots
% if (pf)
hold off
title('Parameter Values');
xlabel('x_1');
ylabel('x_2');
figure(2)
gen=1:GA.NG;
plot(gen,fmn,'r-',gen,fmd,'b',gen,fmx,'g');
legend('Mean','Median','Maximum');
xlabel('Generation');
ylabel('Fitness');
title('Evolution');
% end
% best fitness
[~,i]=max(f);
disp('x*=');
disp(x(:,i))
disp('f(x*)=');
disp(f(i));
end % example1p6A
function x=decode(P,GA)
% decode decodes genes to parameter values
%
% Inputs:
% P = population array
% GA = genetic algorithm parameters
%
% Outputs
% x = parameter array
x=zeros(size(P));
for g=1:GA.Ng
x(g,:)=GA.xmn(g) (GA.xmx(g)-GA.xmn(g))*P(g,:);
end
end
function f=fitness(x)
% fitness computes the fitness
%
% Inputs:
% x = parameter array
%
% Outputs
% f = fitness
x1=x(1,:);
x2=x(2,:);
f=1./((x1.*x2-6).^2 4*(x2-3).^2 1);
end
function M=select(P,f,GA)
% select determines the mating pool
%
% Inputs:
% P = population array
% f = fitness
% GA = genetic algorithm parameters
%
% Outputs:
% M = mating pool array
M=zeros(size(P));
l1=randi([1 GA.Np],GA.Np,1);
l2=randi([1 GA.Np],GA.Np,1);
for i=1:GA.Np
i1=l1(i);
i2=l2(i);
if (f(i1)>=f(i2))
M(:,i)=P(:,i1);
else
M(:,i)=P(:,i2);
end
end
end
function C=children(M,GA)
% children forms children from the mating pool
%
% Inputs:
% M = mating pool array
% GA = genetic algorithm parameters
%
% Outputs:
% C = array of children
% perform simple blend crossover
C=zeros(size(M));
for i=1:GA.Np/2
i2=2*i;
i1=i2-1;
if GA.pc>rand
mn=0.5*(M(:,i1) M(:,i2));
df=(M(:,i2)-M(:,i1))*GA.alpha*rand;
C(:,i1)=mn df;
C(:,i2)=mn-df;
else
C(:,i1)=M(:,i1);
C(:,i2)=M(:,i2);
end
end
% mutation
R=rand(GA.Ng,GA.Np);
index=GA.pm>rand(GA.Ng,GA.Np);
C(index)=R(index);
% gene repair
index=C>1;
C(index)=1;
index=C<0;
C(index)=0;
end
import numpy as np
import math, statistics
import matplotlib.pyplot as plt
def example1p6A(NG, Np, rf, pf):
# example1p6A is a function to generate example 1.6A in
# Power Magnetic Devices: A Multi-Ojective Design Approach
# by S.D. Sudhoff
#
# Call:
# example1p6A(NG,Np,rf,pf)
#
# Input:
# NG = number of generations
# Np = size of population
# rf = report flag (set to 1 to write report)
# pf = plot flag (set to 1 to plot results)
#
# Output:
# All output is textual or graphical
#
# Internal:
# GA = structure of genetic algorithm parameters
# GA.Ng = number of genes
# GA.Np = number in population
# GA.NG = number of generations
# GA.pc = probability of crossover
# GA.pm = probabiligy of gene mutation
# GA.xmn = vector of minimum values for unnormalized genes
# GA.xmx = vector of maximum values for unnormalized genes
# g = generation counter
# P = the population (number of genes by number of individuals)
# PC = copy of the population
# x = uncoded gene values of population
# f = fitness of population
# M = mutated populatin
# fmn = mean fitness of population
# fmx = maximum fitness of population
# fmd = median fitness of population
#
# Version/Date:
# May 7, 2013
#
# Written by:
# S.D. Sudhoff
# Purdue University
# Electrical Engineering Building
# 465 Northwestern Avenue
# West Lafayette, IN 47907-2035
# [email protected]
# 765-497-7648
GA = dict(
Np=np.array(Np),
NG=np.array(NG),
Ng=np.array(2),
pc=np.array(0.5),
alpha=np.array(0.5),
pm=np.array(0.1),
xmn=np.array([0, 0]),
xmx=np.array([5, 5]))
# Init population
P = np.random.rand(GA["Ng"],GA["Np"])
# empty bins fol plotting
fmean = []
fmax = []
fmed = []
# loop over the generations
for g in range(GA["NG"]):
PC = P
x = decode(P,GA)
f=fitness(x)
# if g < GA["NG"]: # g ist immer kleiner als GA["NG"] weil range() von 0->(n-1) geht
# M = select(P,f,GA)
# P = children(M,GA)
M = select(P,f,GA)
P = children(M,GA)
fmean.append(statistics.mean(f))
fmax.append(max(f))
fmed.append(statistics.median(f))
print("x* = {}".format(x[:,1]))
print("f_max = {}\n".format(f.max()))
# plot that stuff
plt.style.use("fivethirtyeight")
plt.plot(np.arange(1,GA["NG"] 1),fmean, label = "mean")
plt.plot(np.arange(1,GA["NG"] 1),fmed, label = "median")
plt.plot(np.arange(1,GA["NG"] 1),fmax, label = "max")
plt.xlabel("Generation")
plt.ylabel("Fitness")
plt.title("Evolution")
plt.axis([0,GA["NG"],0,1.2])
plt.tight_layout()
plt.legend()
plt.show()
# return P
def decode(P,GA):
x = np.zeros(np.shape(P))
for g in range(GA["Ng"]):
x[g,:] = GA["xmn"][g] (GA["xmx"][g]-GA["xmn"][g])*P[g,:]
return x
def fitness(x):
# fitness computes the fitness
#
# Inputs:
# x = parameter array
#
# Outputs
# f = fitness
x1 = x[0,:]
x2 = x[1,:]
f=1/((x1*x2-6)**2 4*(x2-3)**2 1)
return f
def select(P,f,GA):
# select determines the mating pool
#
# Inputs:
# P = population array
# f = fitness
# GA = genetic algorithm parameters
#
# Outputs:
# M = mating pool array
M = np.zeros(np.shape(P))
l1 = np.random.randint(1,GA["Np"] 1,(GA["Np"],1)) #randint is [lower...upper)
l2 = np.random.randint(1,GA["Np"] 1,(GA["Np"],1))
for i in range(GA["Np"]):
i1 = l1[i][0]
i2 = l2[i][0]
if f[i1-1] >= f[i2-1]:
#bei matlab beginnt der index bei 1. python hingegen startet bei 0 und endet bei n-1
M[:,i] = P[:,i1-1]
else:
M[:,i] = P[:,i2-1]
return M
def children(M,GA):
# children forms children from the mating pool
#
# Inputs:
# M = mating pool array
# GA = genetic algorithm parameters
# # Outputs:
# C = array of children
C = np.zeros(np.shape(M))
# perform simple blend crossover
C = np.zeros(np.shape(M))
for i in range(1,math.floor(GA["Np"]/2) 1):
i2 = 2*i
i1 = i2-1
rnd = np.random.rand()
if GA["pc"] > rnd:
mn= 0.5*(M[:,i1-1] M[:,i2-1]) #the index starts from 0 but the counter from 1
df=(M[:,i2-1]-M[:,i1-1])*GA["alpha"]*np.random.rand()
C[:,i1-1]=mn df
C[:,i2-1]=mn-df
else:
C[:,i1-1]=M[:,i1-1]
C[:,i2-1]=M[:,i2-1]
# Mutation
R=np.random.rand(GA["Ng"],GA["Np"])
index = GA["pm"] > np.random.rand(GA["Ng"],GA["Np"])
C[index]=C[index]
# Gene repair
index= C>1
C[index] = 1
index =C <0
C[index] = 0
return C
example1p6A(10000,10,0,0)
uj5u.com熱心網友回復：
盡管我發現了一個錯誤C[index] = C[index]，但C[index]=R[index]我已經完全放棄了上面的代碼，并使用大量print()-commands從頭開始撰寫它，以查看每一步都在做什么。現在我的作業代碼如下：
import numpy as np
import matplotlib.pyplot as plt
import math, statistics
def mygen(NG,Np,rf,pf):
GA = dict(
Ng = np.array(2),
Np = np.array(Np),
NG = np.array(NG),
pc = np.array(0.5),
alpha = np.array(0.5),
pm = np.array(0.1),
xmn = np.array([0,0]),
xmx = np.array([5,5])
)
# Init population
P = np.random.rand(GA['Ng'],GA['Np'])
# print("Iinitial population:\n{}".format(P))
# Empty bins for median and stuff
fmean = []
fmed = []
fmax = []
index_of_max = 0
for g in range(GA['NG']):
# print("Generation {}:".format(g))
x = decode(P,GA)
# print("\n\n")
f = fitness(x)
# print("fitness f() for each individual:\n{}".format(f))
index_of_max = np.unravel_index(np.argmax(f,axis=None),f.shape)
fmean.append(np.mean(f))
fmed.append(np.median(f))
fmax.append(f[index_of_max])
# print("Worst fitness for Individual #{}:{}".format(index_of_min,f[index_of_min]))
# print("Best fitness for Individual #{}:{}".format(index_of_max,f[index_of_max]))
# Find the mating pool
M = select(P,f,GA)
# Create new population
P = children(M,GA)
# Final output
# index = np.unravel_index(np.argmax(f))
i = index_of_max
print("x*:{}".format(x[:,i]))
print("f(x*)={}".format(f[i]))
# Final plots
plt.style.use("fivethirtyeight")
plt.plot(np.arange(1,GA["NG"] 1),fmean,label = "mean")
plt.plot(np.arange(1,GA["NG"] 1),fmax,label = "max")
plt.plot(np.arange(1,GA["NG"] 1),fmed,label = "med")
plt.xlabel("Generation")
plt.ylabel("Fitness")
plt.title("Evolution")
plt.axis([0,GA["NG"],0,1.2])
# plt.xticks(np.arange(1,GA["NG"] 1, 5))
plt.tight_layout()
plt.legend()
plt.show()
def decode(P,GA):
x=np.zeros(np.shape(P))
for g in range(GA['Ng']):
x[g,:] = GA['xmn'][g] (GA['xmx'][g]-GA['xmn'][g])*P[g,:]
# print("decode()\n x{}:\n{}".format(g,x))
return x
def fitness(x):
x1 = x[0,:]
x2 = x[1,:]
f = 1/((x1*x2-6)**2 4*(x2-3)**2 1)
return f
def select(P,f,GA):
M = np.zeros(np.shape(P))
l1 = np.random.randint(0,GA["Np"],(GA["Np"],1))
l2 = np.random.randint(0,GA["Np"],(GA["Np"],1))
for i in range(GA["Np"]):
i1 = l1[i,0]
i2 = l2[i,0]
if f[i1] >= f[i2]:
M[:,i] = P[:,i1]
# print(f[i1])
else:
M[:,i] = P[:,i2]
# print(f[i2])
# print(i1)
return M
def children(M,GA):
C = np.zeros(np.shape(M))
# Simple blend crossover
for i in range(math.floor(GA["Np"]/2)):
i2 = 2*(i 1)
i1 = i2-1
if GA["pc"] > np.random.rand():
mn = 0.5*(M[:,i1-1] M[:,i2-1])
df = (M[:,i2-1]-M[:,i1-1])*GA["alpha"]*np.random.rand()
C[:,i1-1] = mn df
C[:,i2-1] = mn-df
else:
C[:,i1-1] = M[:,i1-1]
C[:,i2-1] = M[:,i2-1]
# Mutation
R = np.random.rand(GA["Ng"],GA["Np"])
index = GA["pm"]>np.random.rand(GA["Ng"],GA["Np"])
C[index] = R[index]
# Gene repair
index =C>1
C[index]=1
index =C<0
C[index]=0
return C
mygen(15,50,1,0)
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