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Avoid using Stead method from GSL above certain threshold. 

Former-commit-id: aa8012deef69ecce95f203b1b5746cfaa0980806
This commit is contained in:
Marek Nečada 2020-03-26 17:14:17 +02:00
parent 1b4b397093
commit 5f729d28a7
1 changed files with 7 additions and 2 deletions
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9
qpms/bessel.c
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@ -48,13 +48,17 @@ static inline complex double spherical_yn(qpms_l_t l, complex double z) {
} }
#endif #endif
// Don't use Stead algorithm from GSL above this threshold (it fails for x's around 1000000 and higher)
static const double stead_threshold = 1000;
// There is a big issue with gsl's precision of spherical bessel function; these have to be implemented differently // There is a big issue with gsl's precision of spherical bessel function; these have to be implemented differently
qpms_errno_t qpms_sph_bessel_realx_fill(qpms_bessel_t typ, qpms_l_t lmax, double x, complex double *result_array) { qpms_errno_t qpms_sph_bessel_realx_fill(qpms_bessel_t typ, qpms_l_t lmax, double x, complex double *result_array) {
int retval; int retval;
double tmparr[lmax+1]; double tmparr[lmax+1];
switch(typ) { switch(typ) {
case QPMS_BESSEL_REGULAR: case QPMS_BESSEL_REGULAR:
retval = gsl_sf_bessel_jl_steed_array(lmax, x, tmparr); retval = (x < stead_threshold) ? gsl_sf_bessel_jl_steed_array(lmax, x, tmparr)
: gsl_sf_bessel_jl_array(lmax, x, tmparr);
for (int l = 0; l <= lmax; ++l) result_array[l] = tmparr[l]; for (int l = 0; l <= lmax; ++l) result_array[l] = tmparr[l];
return retval; return retval;
break; break;
@ -70,7 +74,8 @@ qpms_errno_t qpms_sph_bessel_realx_fill(qpms_bessel_t typ, qpms_l_t lmax, double
break; break;
case QPMS_HANKEL_PLUS: case QPMS_HANKEL_PLUS:
case QPMS_HANKEL_MINUS: case QPMS_HANKEL_MINUS:
retval = gsl_sf_bessel_jl_steed_array(lmax, x, tmparr); retval = (x < stead_threshold) ? gsl_sf_bessel_jl_steed_array(lmax, x, tmparr)
: gsl_sf_bessel_jl_array(lmax, x, tmparr);
for (int l = 0; l <= lmax; ++l) result_array[l] = tmparr[l]; for (int l = 0; l <= lmax; ++l) result_array[l] = tmparr[l];
if(retval) return retval; if(retval) return retval;
retval = gsl_sf_bessel_yl_array(lmax, x, tmparr); retval = gsl_sf_bessel_yl_array(lmax, x, tmparr);