Week 4.1 - Genetic Algorithm
AIM:
* To plot graphs based on the studies done on genetic algorithm
OBJECTIVE :
*To study about the genetic algorithim and stalagmite function. To plot graphs based on the studies done for genetic algorthim
THEORY:
* The algoritham begins by creating a random initial population of individual selections and it keeps on modified the population repetadely creating sequence of new popuation .the algoritham uses the inividuals in the generation to create the next population.
* selecation rules select the individuals called parents that contribute to the population at the generation
* cross over rules combine two parents to form children for the next generation
* mutation rules apply random changes to individual parents to from children
THE FLOWCHART :
What is a stalagmite function:
* Stalagmite function is a mathematical model which helps to generate local minima and maxima .it is a three dimensional function and way the function is designed is that it of local maxima or minima and one glopal maxima or minima. the name stalagmite actually a type of rock formation that arises from the floor of a carve due to accumulation of material deposited on the from ceilling dripping.
syntax for defining 'ga' (genetic algoritham) -matlab
* The 'ga' syntax in matlab is used to find the minimum function using ga. there are several ways to define the 'ga' function depending on the problem being solved .
x=ga(fun,nvars)
X=optimal solution
fun=objective function
nvars=number of variables
x=ga (fun,nvars,A,B,Aeq,Beq,lb,up,nonlcon,intcon ,options)
nonlcon= nonlinear constraints
intcon =integer values
options = optimization options
CODING:
function [f] = stalagmite(input_vector)
a=input_vector(1);
b=input_vector(2);
term1=(sin((5.1*pi*a)+0.5))^6;
term2=exp(-4*log(2)*((a-0.0667)^2)/0.64);
term3=(sin((5.1*pi*b)+0.5))^6;
term4=exp(-4)*log(2)*((b-0.0667)^2)/0.64;
[f]=-(term1*term2*term3*term4); %inverts the objective function
end clear all
close all
clc
% Defining our search space
x = linspace(0,0.6,150);
y = linspace(0,0.6,150);
% Creating a 2Dimensional mesh
[xx,yy] = meshgrid(x,y);
% Evaluating the stalagmite function
for i = 1:length(xx)
for j = 1:length(yy)
input_vector(1)=xx(i,j);
input_vector(2)=yy(i,j);
f(i,j) = stalagmite(input_vector);
end
end
surfc(xx,yy,-f)
shading interp
[x,fval] = ga(@stalagmite,2);
clear all
close all
clc
x = linspace(0,1,150);
y = linspace(0,1,150);
[xx,yy] = meshgrid(x,y);
% Evaluating the stalagmite function
for i = 1:length(xx)
for j = 1:length(yy)
input_vector(1)=xx(i,j);
input_vector(2)=yy(i,j);
f(i,j) = stalagmite(input_vector);
end
end
surfc(xx,yy,-f)
shading interp
tic
% study 1-stalagmite behavior
num_cases = 50;
for i = 1:num_cases
[inputs,fopt(i)] = ga(@stalagmite,2);
xopt(i) = inputs(1);
yopt(i) = inputs(2);
end
study1_time = toc
figure(1)
subplot(2,1,1)
surfc(xx,yy,-f)
hold on
shading interp
plot3(xopt,yopt,-fopt,'Marker','o','MarkerSize',5,'MarkerFaceColor','r')
title('unbounded inputs')
subplot(2,1,2)
plot(-fopt)
xlabel('Iterations')
ylabel('function minimum')
tic
% study 2-statistical behavior -with upper and lower bounds
for i = 1:num_cases
[inputs,fopt(i)] = ga(@stalagmite,2,[],[],[],[],[0;0],[1;1]);
xopt(i) = inputs(1);
yopt(i) = inputs(2);
end
study2_time = toc
figure(2)
subplot(2,1,1)
surfc(xx,yy,-f)
hold on
shading interp
plot3(xopt,yopt,-fopt,'Marker','o','MarkerSize',5,'MarkerFaceColor','r')
title('Bounded inputs')
subplot(2,1,2)
plot(-fopt)
xlabel('Iterations')
ylabel('Function minimum')
% study 3 increasing GA iterations
options = optimoptions('ga')
options = optimoptions(options,'PopulationSize', 150);
tic
for i = 1:num_cases
[inputs,fopt(i)] = ga(@stalagmite,2,[],[],[],[],[0;0],[1;1],[],options);
xopt(i) = inputs(1);
yopt(i) = inputs(2);
end
study3_time = toc
figure(3)
subplot(2,1,1)
hold on
surfc(x,y,-f)
shading interp
plot3(xopt,yopt,fopt,'Marker','o','MarkerSize',5,'MarkerFaceColor','r')
subplot(2,1,2)
plot(-fopt)
xlabel('No. of Iterations')
ylabel('function maximum')
CODING EXPLANATION:
Clear all
close all
clc
* Then' X' array and 'Y' array is defining using 'linspace' command to creat value at 150 equal intervals
* A 2D mesh of x and y array is creating by using 'mesh grid 'command and the number of iterations or cases that the code should perform is defined
* To evaluate the stalagmite function for loop is used where 'i' is intialzied and for every where of 'i' another 'for' loop is used initilize
* The inpu vector values 'xx' 'yy' are defined as stalagmite function for these input vector is defined this will form basic stalagmite function and we can plot its separetly if needed
* After preparing the inputs needed for the function ,next step is to obtain the results for 3 cases of genetic algorthim .in first case or study ,the maximum value of function is founded out with no restrications ,no bound and no limts
* This is done using 'for' loop where we use 'ga' syntax to given values for inputs and optimum max value .the stalagmite function is called 'ga' syntax and number of variables 'nvars' are 2
* To known the time that is taken to solve the loop for 50 iterations ,'tic' and 'toc' command is used before and ofter the loop respectively
* Then function created in the loop is plotted by using 'surfc' command for 'xx,yy and function output'.To neglect the gridlines on the surface and obtain a smooth and clean plot ,'shading interp' command is used .the 'subplot' (2,1,1) is used a plots multiple plots on same figure which also divides figure in grid of 2*1 and axes to placed at 1
