selection - courses2.cit.cornell.edu | cornell university
TRANSCRIPT
![Page 1: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/1.jpg)
Selection
CS 5764
Evolutionary Computation
Hod Lipson
![Page 2: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/2.jpg)
Approaches
• Generational (classic GA)
• Steady state (unsynchronized)
• Distributed (parallel)
![Page 3: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/3.jpg)
Steady State
1. Choose parent(s) at random
2. create offspring
3. Choose someone in population
4. If child better than selected individual, replace it
Produces races on multi-processor architectures
![Page 4: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/4.jpg)
Distributed
![Page 5: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/5.jpg)
Selection
![Page 6: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/6.jpg)
Approaches
• Fitness proportionate
• Rank
![Page 9: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/9.jpg)
Challenges
• Signal to noise
– Small variations in large fitnesses matter
– 103 101 102
![Page 10: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/10.jpg)
Normalization
• Gaussian
– subtract mean, divide by stdev
• Linear
– Bring min-max to [0-1]
• Nonlinear
– Boltzman selection F=exp(f/T)
![Page 11: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/11.jpg)
Replacement
• Random
• Worst (Inverse Boltzman)
• Parent
• Most similar Diversity
![Page 12: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/12.jpg)
Rank based methods
• Truncation: top k% are replicated and
replace bottom 100-k% with variation
• Tournament: Select random k, among
those select top for variation
• (, ) generates new offspring and
uses top to populate the next
generation
• Elitism: Keep the best k solutions
around unmodified
![Page 13: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/13.jpg)
Best
40%
Variation
Worst
60%
Truncation Selection
![Page 14: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/14.jpg)
Sexual Selection
![Page 15: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/15.jpg)
Sexual Selection
![Page 16: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/16.jpg)
Fitness evaluation is costly
• Internal error correction
• Natural selection (expensive)
• Culling at all levels
– Sperm competition
– Sibling rivalry
– Male competition
![Page 17: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/17.jpg)
The role of males
• Males are often smaller and have a shorter life span
• Males are put through more testing: competition with
each other, thrown out of family younger, placed at
(otherwise unnecessary) risk
• Males are more fragile: susceptive various illnesses
• Males have less error correction mechanisms:
Haplodiploidity
• Errors are visible (eg. Via intelligence) to allow sexual
culling be females
![Page 18: Selection - courses2.cit.cornell.edu | Cornell University](https://reader031.vdocuments.site/reader031/viewer/2022021021/620478c4bf47aa594a182ead/html5/thumbnails/18.jpg)
Diversity
• Adapt fitness by similarity
• Adapt selection by similarity