How do I write a partially mapped crossover that can produce multiple pairs of chromosomes

From this link https://www.mathworks.com/matlabcentral/answers/448078-partially-mapped-crossover-function-for-tsp#answer_394090 , I'm able to produce a pair of chromosomes but I want to run the crossover function for multiple times to get multiple pairs of chromosomes.

I have 2 random parents data example,

P1: 1 | 3 7 | 6 4 10

P2: 2 | 3 4 | 7 6 10

The first and last genes (the number underlined) cannot be changed as they are the starting and endpoints. The other four genes are free to exchange at any cut point (need not be the same as the example).

I have tried to put the function into a for loop but it only produces a pair of chromosomes. Alternatively, I have tried to put the for loop inside the function but it results in the crossover function not functioning.

Here is my coding.

for z = 1:4
     a = YY2(:,randi(y4))'; % Fist Vector Needed to be Cross
     b = YY2(:,randi(y4))'; %Second Vector Needed to be Cross
     child1 = zeros(1,size(a,2));
     child2 = zeros(1,size(b,2));
     [~,sizea]=size(a);
     [~,sizeb]=size(b);

 if sizea~=sizeb
     print("a and b are not equal cant do crossover");
 end

 for i=1:100
     r = randi([2,size(b,2)-1],1,2);
     lo = min(r);
     up = max(r);
     if lo==up
         continue
     else
         break
     end
 end

 for i=lo:up
      child1(i)=b(i);
      child2(i)=a(i);
 end

 % child1
    for i=lo:up
        d=0;
        for j=lo:up
            if(a(i)==child1(j))
                d=d+1;
                break;
            end           
        end
        if d==0
         crossover1(i,i,a,sizea,child1);              
        end    
    end

    for q = 1:sizea
        if child1(q)==0
            child1(q)=a(q);
        end       
    end

% child2
for i=lo:up
    d=0;
    for j=lo:up
        if(b(i)==child2(j))
            d=d+1;
            break;
        end           
    end
    if d==0
     crossover2(i,i,b,sizeb,child2);              
    end    
end

for q = 1:sizeb
    if child2(q)==0
        child2(q)=b(q);
    end       
end

S = child1';
T = child2';
odd = 2*z-1;
even = 2*z;
Y2(:,odd) = S;
Y2(:,even) = T;
end

Unrecognized function or variable 'YY2'.

Y2(bus+2,:) = cus_node;
YY4 = Y2;

function  crossover1(n,i,a,sizea,child1)
    for k=1:sizea
        if child1(n) == a(k)
           if child1(k) == 0
              child1(k) = a(i);
              break;
           else
               crossover1(k,i,a,sizea,child1)
           end 
        end
    end
end

function  crossover2(n,i,b,sizeb,child2)
    for k=1:sizeb
        if child2(n) == b(k)
           if child2(k) == 0
              child2(k) = b(i);
              break;
           else
               crossover2(k,i,b,sizeb,child2)
           end 
        end
    end
end

[Debadipto]

Could you please elaborate on the output you're intending to get? Wrapping the function inside a for loop should ideally give you multiple pairs of output. Maybe you can share your code snippet.

[Wan]

For example, I would like to produce 4 pairs of chromosomes :

1 3 4 6 7 10

2 3 7 4 6 10

2 7 3 6 4 10

1 4 7 6 3 10

2 6 7 3 4 10

1 7 4 3 6 10

2 4 6 3 7 10

1 6 4 7 3 10

I have fixed the starting point to be 1 and 2 and the endpoint to be 10. Only the four genes (3,4,6 and 7) will undergo crossover.

Answer 1

[Debadipto]

Hi Wan,

You can use the following script to generate multiple pair of chromosomes:

a = [1 3 4 6 7 10];
b = [2 3 7 4 6 10];
n = 4;
chromosomes = [];

for i = 1:4
    chromosomes(:, :, i) = crossover(a, b);
end
disp(chromosomes)

function child= crossover(a, b)
    % crossover function logic ...
end

Moreover, you can use the “randi” function to generate random vectors for `a` and `b`.

Regards,

Debadipto Biswas