Question

I’m currently trying to realize a very simple example of genetic algorithms.

At one point, you have to do a “Cross-Over” (biology) with two numbers (parents) to get a “child”.

You can find an explanation of Cross-Over here:

How to "crossover" two strings (1234 & abcd -> 12cd & ab34)

(The second illustration, the easier “one-point” Cross-Over is the one I’m trying to do.)

The chromosomes (parents and child) are numbers but the “Cross-Over” will be a bit operation.

I found a solution for one of the “chromosomes”, which is the following :

• Move the bits X amount to the right (>>> operator )
• and then move the bits again X positions but this time to the left (<< operator)

So this would keep the end of one of the chromosomes and fill the beginning with 0s.

But I don’t really know how to solve the problem of the other chromosome and then also do the Cross-Over.

(Probably a XOR once I kept the beginning / end of the chromosomes and filled the rest with 0s.)

Or should I even approach this problem from another angle?

Answer 1

If the fraction of the Cross-Over is p (e.g., p = .25), then this should work:

mask1 = ((0xffff >> 16*p) << 16*p)
mask2 = 0xffff ^ mask1
output1 = (input1 & mask1) ^ (input2 & mask2)
output2 = (input1 & mask2) ^ (input2 & mask1)

A couple of notes:

• This is just pseudocode. You might want some casts in there.
• This treats p differently than you treat it in your comment above. (Just replace p with 1-p to get to your definition of p.)