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JuliaGA/GA.jl
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using StatsBase | |
#= | |
Parents <— {randomly generated population} | |
While not (termination criterion) | |
Calculate the fitness of each parent in the population | |
Children <- 0 | |
While | Children | < | Parents | | |
Use fitnesses to probabilistically select a pair of parents for mating | |
Mate the parents to create children c\ and c<i | |
Children <— Children U {ci,C2} | |
Loop | |
Randomly mutate some of the children | |
Parents <— Children | |
Next generation | |
Use continuous GA, not binary | |
include array of independent variables along with associated range | |
=# | |
function initialize_population(populationSize::Int, chromosomeSize::Int, bounds::Array{Tuple{Float64, Float64},1}) | |
""" | |
Initializes the population based on the given population size and chromosome size | |
Values will be from lb to ub (lower to upper bound) | |
""" | |
# Check to see if we dont have enough bounds or have too many | |
if length(bounds) != chromosomeSize | |
println("Length of bounds ($(length(bounds))) not equal to specified chromosome size ($chromosomeSize)") | |
exit() | |
end | |
# Init population | |
population = Array{Array{Float64}}(0) | |
# Foreach member in population | |
for i = 1:populationSize | |
# Init the member | |
row = [] | |
# Create member elements based on bounds | |
for bound in bounds | |
push!(row, rand(bound[1]:0.10:bound[2])) | |
end | |
# Add another element to the end to keep score | |
push!(row, 1.0) | |
# hcat row, append to 2D population matrix | |
population = push!(population, row) | |
end | |
return population | |
end | |
function score_sort_population(population::Array{Array{Float64}}, fitness_function::Function) | |
""" | |
Args | |
population: The population to score. Must be 2D array of Float64 elements | |
fitness_function: Function to score the population | |
Must be able to take array as argument | |
For example f(x,y) should be f(A) where A[1]=x, A[2]=y | |
Returns scored population. Score is the last element of each chromosome (row) | |
in population | |
""" | |
# Enumerate through population, set last element of each chromosome to score | |
for (index,member) in enumerate(population) | |
population[index][end] = fitness_function(member) | |
end | |
sort!(population, by = x -> x[end]) | |
return population | |
end | |
function create_next_generation(population::Array{Array{Float64}}, recombRate::Float64) | |
""" | |
Creates children given a population and recombination rate | |
Uses an elite selection of 0.10 (rounded up) | |
Creates random chance | |
TODO: Implement ranking | |
""" | |
popSize = length(population) | |
memberSize = length(population[1]) | |
# Init children array | |
children = Array{Array{Float64}}(0) | |
# Elite selection | |
for i in 1:Int(ceil(popSize*0.10)) | |
push!(children, population[i]) | |
end | |
# Generate rest of population | |
while length(children) < popSize | |
# Two random children | |
choices = sample(1:popSize, 2, replace=false) | |
# Check for crossover | |
if rand() < recombRate | |
# Choose xover point | |
# Use -2 since last one is score, and last actual element cant be crossedover since that means there is none | |
xover = rand(1:memberSize-2) | |
child1 = cat(1,population[choices[1]][1:xover],population[choices[2]][xover+1:end]) | |
child2 = cat(1,population[choices[2]][1:xover],population[choices[1]][xover+1:end]) | |
else | |
# Else no crossover, just copy | |
child1 = population[choices[1]] | |
child2 = population[choices[2]] | |
end | |
# Push child 1 and 2 to children array | |
push!(children, child1, child2) | |
end | |
# We might have one extra due to rounding in the elite selection, let's check | |
if length(children) != popSize | |
pop!(children) | |
end | |
return children | |
end | |
function mutate(population::Array{Array{Float64}}, mutateRate::Float64, bounds::Array{Tuple{Float64, Float64},1}) | |
""" | |
Iterates through each chromosome and mutates if needed | |
""" | |
for member in population | |
for i = 1:length(member)-1 | |
if rand() < mutateRate | |
member[i] = rand(bounds[i][1]:0.10:bounds[i][2]) | |
end | |
end | |
end | |
return population | |
end | |
function GA(populationSize::Int, chromosomeSize::Int, fitness_function::Function, bounds::Array{Tuple{Float64, Float64},1}) | |
""" | |
Args | |
populationSize: Total number of chromosomes | |
chromosomeSize: How long each chromosome should be (variables in fitness function) | |
fitness_function: Function to determine fitness of each solution | |
Should take an array as an arg | |
Example: f(x,y,z) = x+y+z | |
should be f(X) = X[1]+X[2]+X[3] | |
in order to allow GA to take in any function with any | |
amount of args to the fitness function | |
bounds: 1D array of tuples, each tuple is the (lower, upper) bounds | |
for each variable. Both lower and upper need to be Float64 types | |
Length should match chromosomeSize | |
e.g: [(1.0,2.0), (3.5,4.5)] | |
""" | |
# Set recombination and mutation rate, lower and upper bound | |
recombRate = 0.7 | |
mutateRate = 0.05 | |
maxIterations = 1000 | |
# First initialize the population | |
population = initialize_population(populationSize, chromosomeSize, bounds) | |
# Then loop for the required iterations | |
bestScores = Array{Float64}(0) | |
i = 0 | |
while i < maxIterations | |
# Score and sort the population | |
population = score_sort_population(population, fitness_function) | |
push!(bestScores,population[1][end]) | |
population = create_next_generation(population, recombRate) | |
population = mutate(population, mutateRate, bounds) | |
i += 1 | |
end | |
println(bestScores) | |
println(population) | |
end | |
function ackley(X) | |
return e - 20*exp(-0.2*sqrt((X[1]^2 + X[2]^2)/2)) - exp((cos(2*pi*X[1]) + cos(2*pi*X[2]))/2) | |
end | |
bounds = [(-2.0,2.0), (-2.0,2.0)] | |
GA(25,2,ackley,bounds) |