stgp_generate_rec.py

def generate_rec(pset, min_, max_, condition, type_=None):
	'''This is a recursive generation function for STGP, which will
	try to generate trees without giving errors for missing primitives.
	Basically, if a primitive fails, it removes it from the
	list of primitives and try again.'''

	height = random.randint(min_, max_)
	def _rec_gen(type_, depth, is_term):
		if is_term:
			try:
				return [random.choice(pset.terminals[type_])]
			except IndexError:
				raise IndexError("Can't find a terminal of type {}".format(type_))
		else:
			# Build a set of functionals for this type
			funcs = list(pset.primitives[type_])
			# Decide once if children will be term (FIXME same value for all the children)
			is_next_term = condition(height, depth)
			while len(funcs):
				try:
					# Pick a random functional
					func = random.choice(funcs)
				except IndexError:
					raise IndexError("Can't find a functional of type {}".format(type_))
				try:
					# Build a list for the functional and its children trees
					res = [func]
					for arg in reversed(func.args):
						res.extend(_rec_gen(arg, depth + 1, is_next_term))
					return res
				except IndexError:
					# Remove the functional from the set and try again
					funcs.remove(func)
			raise IndexError("Can't find a functional of type {}".format(type_))
	return _rec_gen(type_, 0, condition(height, 0))