/// Log upper Pochhammer symbol. double lpochhammer_u(double a, double x) { gsl_sf_result result; int stat = gsl_sf_lnpoch_e(a, x, &result); if (stat != GSL_SUCCESS) { std::ostringstream msg("Error in lpochhammer_u:"); msg << " a=" << a << " x=" << x; throw std::runtime_error(msg.str()); } else return result.val; }
int gsl_sf_legendre_sphPlm_e(const int l, int m, const double x, gsl_sf_result * result) { /* CHECK_POINTER(result) */ if(m < 0 || l < m || x < -1.0 || x > 1.0) { DOMAIN_ERROR(result); } else if(m == 0) { gsl_sf_result P; int stat_P = gsl_sf_legendre_Pl_e(l, x, &P); double pre = sqrt((2.0*l + 1.0)/(4.0*M_PI)); result->val = pre * P.val; result->err = pre * P.err; result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val); return stat_P; } else if(x == 1.0 || x == -1.0) { /* m > 0 here */ result->val = 0.0; result->err = 0.0; return GSL_SUCCESS; } else { /* m > 0 and |x| < 1 here */ /* Starting value for recursion. * Y_m^m(x) = sqrt( (2m+1)/(4pi m) gamma(m+1/2)/gamma(m) ) (-1)^m (1-x^2)^(m/2) / pi^(1/4) */ gsl_sf_result lncirc; gsl_sf_result lnpoch; double lnpre_val; double lnpre_err; gsl_sf_result ex_pre; double sr; const double sgn = ( GSL_IS_ODD(m) ? -1.0 : 1.0); const double y_mmp1_factor = x * sqrt(2.0*m + 3.0); double y_mm, y_mm_err; double y_mmp1; gsl_sf_log_1plusx_e(-x*x, &lncirc); gsl_sf_lnpoch_e(m, 0.5, &lnpoch); /* Gamma(m+1/2)/Gamma(m) */ lnpre_val = -0.25*M_LNPI + 0.5 * (lnpoch.val + m*lncirc.val); lnpre_err = 0.25*M_LNPI*GSL_DBL_EPSILON + 0.5 * (lnpoch.err + fabs(m)*lncirc.err); gsl_sf_exp_err_e(lnpre_val, lnpre_err, &ex_pre); sr = sqrt((2.0+1.0/m)/(4.0*M_PI)); y_mm = sgn * sr * ex_pre.val; y_mmp1 = y_mmp1_factor * y_mm; y_mm_err = 2.0 * GSL_DBL_EPSILON * fabs(y_mm) + sr * ex_pre.err; y_mm_err *= 1.0 + 1.0/(GSL_DBL_EPSILON + fabs(1.0-x)); if(l == m){ result->val = y_mm; result->err = y_mm_err; result->err += 2.0 * GSL_DBL_EPSILON * fabs(y_mm); return GSL_SUCCESS; } else if(l == m + 1) { result->val = y_mmp1; result->err = fabs(y_mmp1_factor) * y_mm_err; result->err += 2.0 * GSL_DBL_EPSILON * fabs(y_mmp1); return GSL_SUCCESS; } else{ double y_ell = 0.0; int ell; /* Compute Y_l^m, l > m+1, upward recursion on l. */ for(ell=m+2; ell <= l; ell++){ const double rat1 = (double)(ell-m)/(double)(ell+m); const double rat2 = (ell-m-1.0)/(ell+m-1.0); const double factor1 = sqrt(rat1*(2*ell+1)*(2*ell-1)); const double factor2 = sqrt(rat1*rat2*(2*ell+1)/(2*ell-3)); y_ell = (x*y_mmp1*factor1 - (ell+m-1)*y_mm*factor2) / (ell-m); y_mm = y_mmp1; y_mmp1 = y_ell; } result->val = y_ell; result->err = (0.5*(l-m) + 1.0) * GSL_DBL_EPSILON * fabs(y_ell); result->err += fabs(y_mm_err/y_mm) * fabs(y_ell); return GSL_SUCCESS; } } }
int gsl_sf_legendre_sphPlm_array(const int lmax, int m, const double x, double * result_array) { /* CHECK_POINTER(result_array) */ if(m < 0 || lmax < m || x < -1.0 || x > 1.0) { GSL_ERROR ("error", GSL_EDOM); } else if(m > 0 && (x == 1.0 || x == -1.0)) { int ell; for(ell=m; ell<=lmax; ell++) result_array[ell-m] = 0.0; return GSL_SUCCESS; } else { double y_mm; double y_mmp1; if(m == 0) { y_mm = 0.5/M_SQRTPI; /* Y00 = 1/sqrt(4pi) */ y_mmp1 = x * M_SQRT3 * y_mm; } else { /* |x| < 1 here */ gsl_sf_result lncirc; gsl_sf_result lnpoch; double lnpre; const double sgn = ( GSL_IS_ODD(m) ? -1.0 : 1.0); gsl_sf_log_1plusx_e(-x*x, &lncirc); gsl_sf_lnpoch_e(m, 0.5, &lnpoch); /* Gamma(m+1/2)/Gamma(m) */ lnpre = -0.25*M_LNPI + 0.5 * (lnpoch.val + m*lncirc.val); y_mm = sqrt((2.0+1.0/m)/(4.0*M_PI)) * sgn * exp(lnpre); y_mmp1 = x * sqrt(2.0*m + 3.0) * y_mm; } if(lmax == m){ result_array[0] = y_mm; return GSL_SUCCESS; } else if(lmax == m + 1) { result_array[0] = y_mm; result_array[1] = y_mmp1; return GSL_SUCCESS; } else{ double y_ell; int ell; result_array[0] = y_mm; result_array[1] = y_mmp1; /* Compute Y_l^m, l > m+1, upward recursion on l. */ for(ell=m+2; ell <= lmax; ell++){ const double rat1 = (double)(ell-m)/(double)(ell+m); const double rat2 = (ell-m-1.0)/(ell+m-1.0); const double factor1 = sqrt(rat1*(2*ell+1)*(2*ell-1)); const double factor2 = sqrt(rat1*rat2*(2*ell+1)/(2*ell-3)); y_ell = (x*y_mmp1*factor1 - (ell+m-1)*y_mm*factor2) / (ell-m); y_mm = y_mmp1; y_mmp1 = y_ell; result_array[ell-m] = y_ell; } } return GSL_SUCCESS; } }
double gsl_sf_lnpoch(const double a, const double x) { EVAL_RESULT(gsl_sf_lnpoch_e(a, x, &result)); }