def _get_running_parameters(self, scale, f, loop=3):
        """Get the running parameters (e.g. quark masses and the strong
        coupling at a given scale."""
        p = {}
        p['alpha_s'] = qcd.alpha_s(scale, self.f, self.parameters['alpha_s'], loop=loop)
        p['m_b'] = qcd.m_b(self.parameters['m_b'], scale, self.f, self.parameters['alpha_s'], loop=loop)
        p['m_c'] = qcd.m_c(self.parameters['m_c'], scale, self.f, self.parameters['alpha_s'], loop=loop)
        p['m_s'] = qcd.m_s(self.parameters['m_s'], scale, self.f, self.parameters['alpha_s'], loop=loop)
        p['m_u'] = qcd.m_s(self.parameters['m_u'], scale, self.f, self.parameters['alpha_s'], loop=loop)
        p['m_d'] = qcd.m_s(self.parameters['m_d'], scale, self.f, self.parameters['alpha_s'], loop=loop)
        # running ignored for alpha_e and lepton mass
        p['alpha_e'] = self.parameters['alpha_e']
        p['m_e'] = self.parameters['m_e']
        p['m_mu'] = self.parameters['m_mu']
        p['m_tau'] = self.parameters['m_tau']
        return p