[Bug-gsl] [bug #45726] Incorrect results of functions bessel_y0, y1 and y2

[Enyi Tang]

URL:
  <http://savannah.gnu.org/bugs/?45726>

                 Summary: Incorrect results of functions bessel_y0, y1 and y2
                 Project: GNU Scientific Library
            Submitted by: eytang
            Submitted on: Mon 10 Aug 2015 01:49:09 AM GMT
                Category: Accuracy problem
                Severity: 3 - Normal
        Operating System: Ubuntu 
                  Status: None
             Assigned to: None
             Open/Closed: Open
                 Release: GSL-1.16
         Discussion Lock: Any

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Details:

It seems when the input is large, the function gsl_sf_bessel_y0,
gsl_sf_bessel_y1, and gsl_sf_bessel_y2 outputs wrong result. It should be near
0, but the outputs from GSL diverge.

A test program is attached, it shows the results as follows with the latest
version of GSL in git. The version hash is
867624b55b20de8da80d23d90549c74ec24cb3a6 from Aug. 7, 2015.


gsl_sf_bessel_y0(1.000000e+17): 0.000000 
gsl_sf_bessel_y1(1.000000e+17): 0.000000 
gsl_sf_bessel_y2(1.000000e+17): -0.000000 
gsl_sf_bessel_y0(1.000000e+18): 0.000000 
gsl_sf_bessel_y1(1.000000e+18): 0.000000 
gsl_sf_bessel_y2(1.000000e+18): -0.000000 
gsl_sf_bessel_y0(1.000000e+19): 12.464496 
gsl_sf_bessel_y1(1.000000e+19): 2.888382 
gsl_sf_bessel_y2(1.000000e+19): -12.464496 
gsl_sf_bessel_y0(1.000000e+20): 28616622845397049540608.000000 
gsl_sf_bessel_y1(1.000000e+20): -9155440021830429048832.000000 
gsl_sf_bessel_y2(1.000000e+20): -28616622845397049540608.000000 
gsl_sf_bessel_y0(1.000000e+21): 286162998538776396548812505696174080.000000 
gsl_sf_bessel_y1(1.000000e+21): -92157107960277832260219441795563520.000000 
gsl_sf_bessel_y2(1.000000e+21): -286162998538776359655324358277070848.000000 
gsl_sf_bessel_y0(1.000000e+22): 569749214880064236122434006444167659520.000000

gsl_sf_bessel_y1(1.000000e+22): 183552123001419854904449771500981977088.000000

gsl_sf_bessel_y2(1.000000e+22):
-569749214880064236122434006444167659520.000000  



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File Attachments:


-------------------------------------------------------
Date: Mon 10 Aug 2015 01:49:09 AM GMT  Name: gslbesselytest.c  Size: 615B  
By: eytang

<http://savannah.gnu.org/bugs/download.php?file_id=34617>

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