EE4047_Part2

# Population pool holds all the chromosomes usually 20

• Notes
• 20

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Population pool holds all the chromosomes (usually 20 individuals or above) Every chromosome is a potential solution of a problem The Quality of a chromosome is governed by a Fitness evaluation process (Objective Function) Head color size Body color feet body wings head Antennae Fitness Functions 1. Head: 1. All corrected = 8 2. 1 bit corrected= 4 3. All wrong = 0 2. Body: 1. All corrected = 8 2. 2 bits corrected = 4 3. 1 bit corrected = 2 4. All wrong = 0 3. Wings: 1. All corrected = 6 2. Otherwise = 0 4. Size: 1. Corrected size = 8 2. One size level difference = 4 3. Two size levels difference = 2 4. Three size levels difference = 0

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Selection - Proportionate scheme Roulette Wheel Selection 10 18 22 Roulette Wheel I II III 1 10 11 32 33 50 Roulette Wheel Selection 1. Sum the fitness of all the population members; named as total fitness ( F = 22+10+18 ) 2. Generate a random number (n) between 1 and total fitness F (for example: n=25 ) 3. Return the first population member whose fitness added to the fitness of the preceding population members, is greater than or equal to n . (for example: 10+22>25 ) Rationale fitter individual higher chance However, fittest may not be the best
Crossover A major operation in GA A technique to combine the genes of two parents A crossover rate to govern the probability of the operation (usually very high, 0.6- 1.0) Offspring may be the same as their parents Single Point Crossover

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Mutation A background operation with low operational rate (<0.1) A bitwise operation applied to each offspring after crossover Provide the missing gene Increase the randomness Mutation
Selection window of functions and parameters Generation

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A sample result of the program Best fitness value plot
Average fitness value plot General Rules of Simple GA Homogenous chromosome structure Finite population size, and it is maintained in evolution process High crossover rate & Low mutation rate Replacement: Generational or steady state

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Analogue DNA
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• Fall '09
• KITSANGTSANG
• DNA, City University of Hong Kong, Holliday Model, GTG ACG CTG

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