double PolyaGamma::draw_sum_of_gammas(double n, double z, RNG& r) { double x = 0; double kappa = z * z; for(int k=0; k < T; ++k) x += r.gamma_scale(n, 1.0) / (bvec[k] + kappa); return 2.0 * x; } // draw_sum_of_gammas