1) Tournament selection has issues of not sampling all individuals in a population and not selecting some individuals. 2) Cooperative selection is proposed as an improvement that is more altruistic. It works by having the better of two randomly sampled individuals be selected for breeding, while the other individual is helped by taking the average fitness of the two. 3) This process is illustrated through an example population where cooperative selection results in all individuals being both sampled and selected for breeding, avoiding the problems with tournament selection.

1. Cooperative Selection:
Improving Tournament Selection via Altruism
J.L.J. Laredo, S. Nielsen, G. Danoy,
P. Bouvry, C.M. Fernandes
University of Luxembourg, University of Lisbon

2. Scope
Cooperative Selection is an altruistic
improvement of Tournament Selection…
…but, what´s wrong with Tournament Selection?

3. What is cool?

4. What is wrong ?
(Poli05) points out
the not-sampling and
the not-selection issues

5. What is wrong ?
Not-sampling
Population at generation x
n individuals

6. What is wrong ?
Not-sampling
Population at generation x
Sampling 1
n individuals
Selection 1

7. What is wrong ?
Not-sampling
Population at generation x
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding

8. What is wrong ?
Not-sampling
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding

9. What is wrong ?
Not-sampling
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
n x
n

10. What is wrong ?
Not-sampling
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
n x
n
Was sampled at all?

11. What is wrong ?
Not-sampling
Was sampled at all?
The answer is:
might be not!
Good news:
(Poli05) proposes a solution to the not-sampling issue

12. What is wrong ?
Not-selection
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
n x
n

13. What is wrong ?
Not-selection
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
Population at generation x
Population at generation x+1
Sampling 1
n individuals
Sampling 2
Selection 1
Selection 2
Breeding
n x
n
Were they ever selected?

14. What is wrong ?
Not-selection
Were they ever selected?
The answer is also:
might be not!
So far… there are no good news

15. Cooperative Selection
2 24 4 56 64 45 34 2 24 4 56 64 45 34
Tournament Selection Cooperative Selection
A B C D E F G A B C D E F G

16. 2 24 4 56 64 45 34 2 24 4 56 64 45 34
Sampling Sampling
1st mate
Cooperative Selection
Tournament Selection Cooperative Selection
A B C D E F G A B C D E F G

17. 2 24 4 56 64 45 34 2 24 4 56 64 45 34
64 64
Selection Selection
1st mate
Cooperative Selection
Tournament Selection Cooperative Selection
E E
A B C D E F G A B C D E F G

18. 2 24 4 56 64 45 34 2 24 4 56 64 45 34
24+56
2
=40
Selection Altruism
1st mate
Cooperative Selection
Tournament Selection Cooperative Selection
64 64
E E
A B C D E F G A B C D E F G

19. 2 24 4 56 64 45 34 2 24 4 56 40 45 34
24+56
2
=40
Selection Altruism
1st mate
Cooperative Selection
Tournament Selection Cooperative Selection
64 40
E E
A B C D E F G A B C D E F G

20. 2 24 4 56 64 45 34 2 24 4 56 40 45 34
2nd mate
Cooperative Selection
Tournament Selection Cooperative Selection
Sampling Sampling
A B C D E F G A B C D E F G
64 40
E E

21. 2 24 4 56 64 45 34 2 24 4 56 40 45 34
45
Selection Selection
2nd mate
64
Cooperative Selection
Tournament Selection Cooperative Selection
A B C D E F G A B C D E F G
64 40
E EE F

22. 2 24 4 56 64 45 34 2 24 4 56 40 45 34
2nd mate
4+40
2
=22
Cooperative Selection
Tournament Selection Cooperative Selection
45
Selection Altruism
64
A B C D E F G A B C D E F G
64 40
E EE F

23. 2 24 4 56 64 45 34 2 24 4 56 40 22 34
2nd mate
4+40
2
=22
Cooperative Selection
Tournament Selection Cooperative Selection
22
Selection Altruism
64
A B C D E F G A B C D E F G
64 40
E EE F

24. 2 24 4 56 64 45 34 2 24 4 56 40 22 34
Cooperative Selection
Tournament Selection Cooperative Selection
22
Breeding
6464 40
E EE FBreeding

25. 2 24 4 56 64 45 34 2 24 4 56 40 22 34
Cooperative Selection
Tournament Selection Cooperative Selection
22
Breeding
6464 40
E EE FBreeding

26. Cooperative Selection
2 24 4 56 64 45 34 2 24 4 56 40 22 34
Tournament Selection Cooperative Selection
22
Breeding
6464 40
E EE FBreeding

27. Cooperative Selection
2 24 4 56 64 45 34 2 24 4 56 40 22 34
Tournament Selection Cooperative Selection
22
Breeding
6464 40
E EE FBreeding

28. Thanks for your attention