Lecture 18 - Genetic Algorithms Flashcards
What are two sources of variation in a gene pool?
Mutation
Crossover
How does mutation modify a gene?
Random modification - usually detrimental
How does crossover modify a gene?
Corresponding portions of two genes are swapped
What is the cycle of basic genetic alrogithms
Evaluation - Selection - Reproduction
What is the typical value of the mutation rate and why is it so low?
10-3
So low because it typically introduces harmful changes, rather than beneficial
Why would a system that only adapted through mutation not be a good idea?
It would adapt very slowly because most mutations would not be helpful. Much faster to combine genes
What is uniform one-point crossover?
Randomly select a point somewhere along the chromosome
Exchange the portions of the two chromosomes after the selected point
What is the typical crossover rate? Why is this rate chosen?
0.5-0.8
Allows a good number to remain unchanged and also a good number to change
Why would a system that only adapted using crossover not be a great idea?
It would adapt quickly but might never find an optimal solution - no new genes would ever be introduced
Crossover and Mutation each have different jobs. What are they?
Mutation ensures the whole solution space is searched
Crossover accelerates the search process
In genetic programming, the population is made up of
computer programs
In genetic programming, the evolving population is made of ______ rather than strings
Trees
How does crossover work with trees?
Randomly select a node in both trees
Swap the subtrees
In tree crossover, node selection is biased. How and why?
Biased to select non-terminal nodes
Swapping a terminal node is basically useless
What two mutation methods exist for trees?
Subtree mutation
Point mutation
