bugGNU Scientific Library - Bugs: bug #45726, Incorrect results of functions...


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bug #45726: Incorrect results of functions bessel_y0, y1 and y2

Submitted by:  Enyi Tang <eytang>
Submitted on:  Mon 10 Aug 2015 01:49:09 AM UTC  
Category: Accuracy problemSeverity: 3 - Normal
Operating System: Ubuntu Status: None
Assigned to: NoneOpen/Closed: Open
Release: GSL-1.16

Thu 13 Aug 2015 06:09:00 AM UTC, comment #1:

The fixing suggestion is submitted with Bug #45746. I believe it is also helpful in fixing bug #36152.

Enyi Tang <eytang>
Mon 10 Aug 2015 01:49:09 AM UTC, original submission:

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

Enyi Tang <eytang>


Attached Files
file #34617:  gslbesselytest.c added by eytang (615B - application/octet-stream)


Depends on the following items: None found

Items that depend on this one: None found


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    Date Changed By Updated Field Previous Value => Replaced By
    Mon 10 Aug 2015 01:49:10 AM UTCeytangAttached File-=>Added gslbesselytest.c, #34617

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