c++ Genetic Algorithm Mutation error

问题

I Have a problem with the mutation function within my genetic Algorithm. I can't quite see what I am doing wrong either. I've looked at this code for a while and I think the logic is correct, it's just not producing the results i want.

The problem When i output the Binary array located in the Child Struct, If mutation has occured on any of the bits, then a random number will be changed, and not the one that should be.

for example

0000000 is the binary string
mutation has occured on the second bit
0001000 would be the result

This section is located within the main.

for (int Child = 0; Child < ParentNumberInit; Child++)
{
    cout << endl;
    mutation(child[Child],Child);
}

This is the mutation function

void mutation(struct Parent Child1,int childnumber)
{
    int mutation; // will be the random number generated

    cout << endl << "Child " << (childnumber+1) << endl;

    //loop through every bit in the binary string
    for (int z = 0; z < Binscale; z++)
    {
        mutation = 0;   // set mutation at 0 at the start of every loop
        mutation = rand()%100;      //create a random number

        cout << "Generated number = " << mutation << endl;

        //if variable mutation is smaller, mutation occurs
        if (mutation < MutationRate)
        {
            if(Child1.binary_code[z] == '0')
                Child1.binary_code[z] = '1';
            else if(Child1.binary_code[z] == '1')
                Child1.binary_code[z] = '0';
        }
    }
}

It's being outputted in the main like this

    for (int childnumber = 0; childnumber < ParentNumberInit; childnumber++)
    {
        cout<<"Child "<<(childnumber+1)<<" Binary code = ";
        for (int z = 0; z < Binscale; z ++)
        {
        cout<<child[childnumber].binary_code[z];
        }
        cout<<endl;
     }

回答1:

You can't throttle the multation rate this way. You need to separate the mutated bit from the probability of the mutation occuring.

for (int z = 0; z < Binscale; z++)     
{         
    if (rand() % 100 < MutationRate)        
    {
        // flip bit             
        Child1.binary_code[z] += 1; 
        Child1.binary_code[z] %= 2;
    }
}

Even simpler way to flip bit:

Child1.binary_code[z] ^= 1;

回答2:

try this:

void mutation(Parent& Child1,int childnumber)

来源：https://stackoverflow.com/questions/4725515/c-genetic-algorithm-mutation-error

标签

c++

genetic-algorithm

mutation