I’m stuck on chapter 7. The fitness function implementation is acting weird in that the chromosome does not always follow a binary digit representation, which then raises an error. I think it’s some sort of overflow happening in the Bitwise.bxor call but not sure how to troubleshoot. Here’s what I’m seeing:
GENES: [0, 1, 2, 3, 4, 5, 7, 8]
** (ArgumentError) errors were found at the given arguments:
* 1st argument: not a textual representation of an integer
:erlang.binary_to_integer("01234578", 2)
scripts/codebreaker.exs:22: Codebreaker.fitness_fun/1
My code is below. You can see I tried to use Integer.undigits first but that gives an error of invalid digit 2 in base 2.
def fitness_fun(chromosome) do
IO.inspect(chromosome.genes, label: :GENES)
target = "ILoveGeneticAlgorithsm"
encrypted = 'LIjs`B`kqlfDibjwlqmhv'
cipher = fn word, key -> Enum.map(word, &rem(Bitwise.bxor(&1, key), 32_768)) end
# key = Integer.undigits(chromosome.genes, 2)
key =
chromosome.genes
|> Enum.map_join(&Integer.to_string(&1))
|> String.to_integer(2)
guess = List.to_string(cipher.(encrypted, key))
String.jaro_distance(target, guess)
end
If I rescue the error I just end up with convergence on a bad chromosome for some reason.
I ran the author’s provided code sample for the chapter and have the same issue. Or, I did until I recompiled everything. So something is off in my actual Genetic library code not in the script itself.
Okay to ignore all that above. I had implemented a chromosome repair function that was specific to one chromosome type and it was screwing things up. So I don’t get that error but currently my code is converging on a fitness of about 0.97 and never completing. Guess I have to get through the rest of the chapter.
