遗传算法Python实现

悠悠 2022-01-27 06:19 275阅读 0赞

### 遗传算法Python实现 ###

*  瞎BB
 *  代码
 *   *  导入库以及参数设置
     *  目标函数
     *  生成C行R列的值在0-1的数组
     *  混沌函数
     *  二进制转十进制
     *  个体按值从大到小排序
     *  交叉变异
     *  适应度函数
     *  主函数

# 瞎BB #

# 代码 #

## 导入库以及参数设置 ##

import pandas as pd
    import numpy as np
    import matplotlib.pyplot as plt
    import math
    import random
    
    #range of variable
    bounds = np.array([-2,2])
    #begin of variable
    boundsbegin = bounds[0]
    #end of variable
    boundsend = bounds[1]
    precision = 0.0001
    #calc the BitLength
    BitLength = math.ceil(np.log2((boundsend - boundsbegin) / precision))
    #init
    popsize = 100
    Generationmax = 100
    pmut = 0.09

## 目标函数 ##

def targetfun(x):
        value = 200 * math.exp(-0.05 * x) * math.sin(x)
        return value

## 生成C行R列的值在0-1的数组 ##

def random_random(C,R):
        rand=[]
        for i in range(C*R):
            rand.append(random.random())
        rand=np.array(rand)
        return rand.reshape(C,R)

## 混沌函数 ##

def chaos(size):
        chaos_cro = np.zeros(size)
        chaos_cro[0] = random.random()
        for j in range(1,size):
                chaos_cro[j] = 4 * chaos_cro[j - 1] * (1 - chaos_cro[j - 1])
        return chaos_cro[-1]

## 二进制转十进制 ##

def transform2to10(sample):
        BitLength = len(sample)
        x=sample[-1]
        for i in range(1,BitLength):
            x=x+sample[-i-1]*np.power(2,i)
        return x

## 个体按值从大到小排序 ##

def rank(population):
        popsize = population.shape[0]
        BitLength = population.shape[1]
        fitvalue = np.zeros(popsize).reshape(popsize,1)
        for i in range(popsize):
            x = transform2to10(population[i])
            #tansform to range of variable
            xx=boundsbegin + x * (boundsend - boundsbegin) / (np.power(boundsend,BitLength)-1)
            fitvalue[i,0]=targetfun(xx)
        #make fitvalue(j)<fitvalue(j+1)
        res = np.concatenate((population,fitvalue),axis = 1)
        res=pd.DataFrame(res)
        population = res.sort_values(by=BitLength)
        population = np.array(population)
        population = population[:,0:BitLength]
        return population

## 交叉变异 ##

def cro_mut_improve(population,rate_mut):
        #seln:two individuals
        popsize = population.shape[0]
        BitLength = population.shape[1]
        population = rank(population)
        #crossover
        pop=popsize
        chaos_cro = np.zeros(BitLength)
        
        if popsize % 2 == 1:
            pop = popsize - 1
            
        for i in range(0,pop,2):
            chaos_cro = chaos(BitLength)
            chao = math.floor(chaos_cro * BitLength)
            temp = population[i,chao]
            population[i,chao] = population[i+1,chao]
            population[i + 1,chao] = temp
        
        #mutation
        by = np.array([])
        n = len(by)
        #generate random individuals to mutate
        while n == 0:
            by = random_random(1,popsize)<rate_mut
            for i in by[0]:
                if i:
                    n+=1
        num_mut = n
        for k in range(popsize):
            if by[0,k] == True:
                chaos_mut = np.zeros(BitLength)
                chaos_mut[0] = random.random()
                for t in range(1,BitLength):
                    chaos_mut[t] = 4 * chaos_mut[t - 1] * (1 - chaos_mut[t - 1])
                position = np.floor(BitLength * random_random(1,2))
                position.astype(np.int16)
                population[k,int(position[0,0])] = np.round(chaos(BitLength))
                population[k,int(position[0,1])] = np.round(chaos(BitLength))
        return population

## 适应度函数 ##

def fitness(population):
        #population=pd.DataFrame(population)
        popsize = population.shape[0]
        BitLength = population.shape[1]
        cumsump = np.zeros(popsize).reshape(1,popsize)
        fitvalue = np.zeros(popsize).reshape(1,popsize)
        for i in range(popsize):
            x = transform2to10(population[i])
            #tansform to range of variable
            xx = boundsbegin + x * (boundsend - boundsbegin) / (np.power(boundsend,BitLength) - 1)
            fitvalue[0,i] = targetfun(xx)
        #ensure fitvalue>0
        fitvalue = fitvalue+230
        fsum = fitvalue.sum(1)[0]
        Pperpopulation = fitvalue / fsum
        cumsump[0] = Pperpopulation[0]
        for i in range(1,popsize):
            cumsump[0,i] = cumsump[0,i-1] + Pperpopulation[0,i]
        res = np.concatenate((fitvalue,cumsump),axis = 0)
        return res

## 主函数 ##

ymax=np.zeros(Generationmax+1)
    ymean=np.zeros(Generationmax+1)
    xmax=np.zeros(Generationmax+1)
    #generate random population
    population = np.round(random_random(popsize,BitLength))
    #calc fitness return fitvalue and sum of probability
    res=fitness(population)
    fitvalue = res[0]
    cumsump = res[1]
    #main code
    Generation=1
    while Generation<Generationmax+1:
        population=cro_mut_improve(population,pmut)
        res=fitness(population)
        fitvalue = res[0]
        cumsump = res[1]
        fmax = np.max(fitvalue)
        for i in range(popsize):
            if fitvalue[i]==fmax:
                nmax = i
                break
        fmean = np.mean(fitvalue,axis = 0)
        ymax[Generation] = fmax
        ymean[Generation] = fmean
        x = transform2to10(population[nmax])
        xx = boundsbegin + x * (boundsend-boundsbegin) / (pow(boundsend,BitLength)-1)
        xmax[Generation] = xx
        Generation += 1
    #Generation=Generation-1;
    Bestpopulation = np.max(xmax)
    BestValue = targetfun(Bestpopulation)
    print(Bestpopulation)
    print(BestValue)
    
    x=[]
    y=[]
    for i in range(400):
        t=-2+0.01*i
        x.append(t)
        y.append(targetfun(t))
    plt.scatter(x, y)