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  Topic: Evolutionary Computation, Stuff that drives AEs nuts< Next Oldest | Next Newest >  

Posts: 2723
Joined: Sep. 2006

(Permalink) Posted: July 03 2009,17:01   

Quote (slpage @ June 23 2009,19:10)
Constant population size is one of my pet peeves with Haldane's model as well.

Experimenting with Gregor's Bookkeeper.

VARIABLE POPULATION and FECUNDITY: Setting the number of Parents and the number of Children such that they vary (e.g. 20% relative standard deviation), they tend to achieve a higher fitness. This is apparently because when the population bottlenecks, it weeds out the weaklings. This is somewhat analogous to variations in climate, such as plenitude followed by drought.

TIME: The typical pattern is to watch the fitness slowly ebb away, but then suddenly spring back. If you quit too soon, you would never see this. As long as the population is large enough to be reasonably stable to avoid extinction for long enough, you will see a sawtooth pattern; a slow slide down in fitness, then a sudden increase as a significant favorable mutation sweeps through the population.

DOMINANCE: Still not happy with this feature. As might be expected, setting the fitter allele to be more dominant leads to greater fitness. This might be considered a cheat though. Setting an arbitrary allele to be dominant, it still often leads to greater fitness. An interesting test was to set dominance on a sliding scale, 1/G for G = 1 to numG (G for gene). This means that for some genes, the dominant gene is deleterious, for others favorable. Interestingly, this also leads to greater fitness.

SHAKING the BOX: It almost seems that anything that adds a bit of complex motion allows those with the highest fitness to rise to the top. Need more data.

DIFFERENCES between Gregor's Bookkeeper and Mendel's Accountant:

  * Multiplicative fitness.
  * Roulette Wheel mating, rather than the odd "divide by random" method.
  * Can handle very large populations and generations—if you're willing to wait.
  * Raised limit on the effect of favorable mutations. Adjusted some other settings.


You never step on the same tard twice—for it's not the same tard and you're not the same person.

  418 replies since Mar. 17 2009,11:00 < Next Oldest | Next Newest >  

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