Evolutionary algorithm: Difference between revisions
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weasel()</lang>
=={{header|Erlang}}==
<lang erlang>module(evolution).
-export([run/0]).
% Evolution parameters
-define(MUTATE, 0.05).
-define(POPULATION, 100).
-define(TARGET, "METHINKS IT IS LIKE A WEASEL").
-define(MAX_GENERATIONS, 1000).
% Exported functions
run() ->
evolve_gens().
% Internal functions
evolve_gens() ->
Initial = random_string(length(?TARGET)),
evolve_gens(Initial,0,fitness(Initial)).
evolve_gens(Parent,Generation,0) ->
io:format("Generation[~w]: Achieved the target: ~s~n",[Generation,Parent]);
evolve_gens(Parent,Generation,_Fitness) when Generation == ?MAX_GENERATIONS ->
io:format("Reached Max Generations~nFinal string is ~s~n",[Parent]);
evolve_gens(Parent,Generation,Fitness) when Generation rem 10 == 0 ->
io:format("Generation[~w]: ~s, Fitness: ~w~n",
[Generation,Parent,Fitness]),
Child = evolve_string(Parent),
evolve_gens(Child,Generation+1,fitness(Child));
evolve_gens(Parent,Generation,_Fitness) ->
Child = evolve_string(Parent),
evolve_gens(Child,Generation+1,fitness(Child)).
fitness(String) -> fitness(String, ?TARGET).
fitness([],[]) -> 0;
fitness([H|Rest],[H|Target]) ->
fitness(Rest,Target);
fitness([_H|Rest],[_T|Target]) ->
1+fitness(Rest,Target).
mutate(String) -> mutate(String,[]).
mutate([],Acc) ->
lists:reverse(Acc);
mutate([H|T],Acc) ->
Mutate = random:uniform(),
if
Mutate < ?MUTATE ->
mutate(T,[random_character()|Acc]);
Mutate >= ?MUTATE ->
mutate(T,[H|Acc])
end.
evolve_string(String) ->
evolve_string(String,?TARGET,?POPULATION,String).
evolve_string(_,_,0,Child) -> Child;
evolve_string(Parent,Target,Population,Best_Child) ->
Child = mutate(Parent),
case fitness(Child) < fitness(Best_Child) of
true ->
evolve_string(Parent,Target,Population-1,Child);
false ->
evolve_string(Parent,Target,Population-1,Best_Child)
end.
random_character() ->
case R=random:uniform(27)-1 of
26 -> $ ;
R -> $A+R
end.
random_string(Length) -> random_string(Length,[]).
random_string(0,Acc) ->
Acc;
random_string(N,Acc) when N > 0 ->
random_string(N-1,[random_character()|Acc]).
</lang>
=={{header|F Sharp|F#}}==
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