def select_algorithm
      return if algorithm
      max = Settings.instance.sweep_cutoff
      n = @target.count_parameter_permutations
      if n < max
        @algorithm = ParameterSweeper.new(@target.parameters, @id)
      else
        @algorithm = TabuSearch.new(@target.parameters, @id)
      end
    end
def select_algorithm
      return if algorithm
      max = Settings.instance.sweep_cutoff
      n = @target.count_parameter_permutations
      if n < max
        @algorithm = ParameterSweeper.new(@target.parameters, @id)
      else
        @algorithm = TabuSearch.new(@target.parameters, @id)
      end
    end
select the optimisation algorithm to use