first prototype for the evolutionary algorithm and a very simple example

prototype.jl

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+#--- Abstract evolutionary framework:
+# TODO mutation
+# TODO keep only children better than parents
+
+
+# Simple evolutionary algorithm without mutation:
+function evolution(initial_generation,
+                   replicator_function,
+                   fitness_function,  
+	               stopping_criterion)
+
+	current_generation = initial_generation #TODO make copy?
+	generation_counter = 0
+
+	print_generation(0,current_generation)
+
+	while( ! stopping_criterion(current_generation, generation_counter))
+
+
+		# Pair up randomly:
+		shuffle!(current_generation) # in-place shuffle
+
+		# Replicate:
+		n = length(current_generation)
+		for i = 1:n
+			parent1 = current_generation[i]
+			j = (i % n) + 1 # Can Julia also do arrays starting at 0? That would be nice!
+			parent2 = current_generation[j]
+			children = replicator_function(parent1, parent2)
+			#println("Pair $(dec(parent1,10)) with $(dec(parent2,10)) -> $(map(dec,children,10))")
+			current_generation = append(current_generation, children)
+		end
+
+		sort!(current_generation) #todo sort with fitness function
+		current_generation = current_generation[1:n]
+		generation_counter = generation_counter + 1
+		print_generation(generation_counter, current_generation)
+	end
+
+	return current_generation[1]
+
+end
+
+
+#--- Test case: numbers
+
+# Simplest fitness function: return argument itself
+function fitness(x::Int32)
+	return x
+end
+
+function print_generation(i, specimens)
+	print("Generation $(dec(i,3)): ")
+	println(map(hex,specimens,8))
+end
+
+# Simple replicator function:
+function combine_integers(parent1::Uint32,parent2::Uint32)
+	low_bits = randi(Uint32)
+	high_bits = ~low_bits
+
+	mutation_bit = 2 ^ randi((1,32))-1
+	child1 = (parent1 & high_bits) | (parent2 & low_bits)
+	child1 = child1 $ mutation_bit
+	child1 = convert(Uint32, child1)
+
+	mutation_bit = 2 ^ randi((1,32))-1
+	child2 = (parent1 & low_bits ) | (parent2 & high_bits)
+	child2 = child2 $ mutation_bit
+	child2 = convert(Uint32, child2)
+
+	return [child1, child2]
+end
+
+# Simple stopping criterion:
+function stop_after_10(generation, counter)
+	if counter > 100
+		return true
+	end
+
+	return generation[1] < 5
+end
+
+
+#--- START
+
+println()
+println("Very simple example: shrink numbers until they approach zero:")
+println()
+
+initial_generation = [randi(Uint32) | i=1:5]
+winner = evolution(initial_generation, combine_integers, fitness, stop_after_10)
+
+println()
+println("And the winner is: $winner")
+println()