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local Grammar = require 'grammar'
local GA = require 'ga'
local production = {}
production["<start>"]={{'<expr>'}}
production["<expr>"]={ {'<var>'}, {'(', '<expr>', '<op>', '<expr>', ')'} }
production["<op>"]={ {'+'}, {'-'}, {'*'}, {'/'} }
production["<var>"]={ {'x'} }
local grammar = Grammar.createGrammar(production)
math.randomseed(0)
function randomGenome()
local len = math.ceil(math.random() * 256)
local genome = {}
for i=1,len do
table.insert(genome, math.floor(256 * math.random()))
end
return genome
end
function randomPop()
local pop = {}
for n=1,1000 do
table.insert(pop, randomGenome())
end
return pop
end
function evaluate(genome)
local s = 'return function(x) return ' .. grammar:expand(genome) .. ' end'
local f = assert(loadstring(s))()
local target = function(x) return (x*x*x*x) + (x*x*x) + (x*x) + (x) end
local cost = 0
for n=0,100 do
x = (n-50)/50
ok, y = pcall(f, x)
if (not ok) or (y ~= y) then
cost = cost + 100
else
cost = cost + math.abs(y - target(x))
end
end
return -((0.0001*#s) + cost)
end
local ga = GA.createGA(randomPop(), {
evaluate=evaluate,
crossover=function(a, b)
local crossoverPoint = math.ceil(#a * math.random())
local new = {}
for i=1,#b do
table.insert(new, (i>=crossoverPoint and b[i]) or a[i])
end
return new
end,
mutate=function(a)
local new = {}
for i,v in ipairs(a) do new[i] = v end
local mutationPoint = math.ceil(#a * math.random())
new[mutationPoint] = math.floor(256 * math.random())
return new
end,
})
for n=1,100 do
print(ga:step())
print(grammar:expand(ga.population[ga.bestMember]))
end
-- for k,v in ipairs(ga.population) do
-- print(k, '(', v[1], v[2], v[3], ')', evaluate(v))
-- end
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