# Reset the search from the initial state.
	# Is used at the beginning and with `iterative_deepening`.
	private fun start
	do
		assert todo.is_empty
		depth_limit_reached = 0
		var initial_node = problem.initial_node
		if memorize and not memorize_late then memory[initial_node.state] = initial_node
		initial_node.id = nodes
		nodes += 1
		todo.add initial_node
	end