[Bug-gsl] [bug #52359] Unexpected results in airy_Ai function

[Patrick Alken]

URL:
  <http://savannah.gnu.org/bugs/?52359>

                 Summary: Unexpected results in airy_Ai function
                 Project: GNU Scientific Library
            Submitted by: psa
            Submitted on: Tue 07 Nov 2017 03:32:37 PM UTC
                Category: Runtime error
                Severity: 3 - Normal
        Operating System: 
                  Status: None
             Assigned to: None
             Open/Closed: Open
                 Release: 
         Discussion Lock: Any

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Details:

The GSL’s airy_Ai function gsl_sf_airy_Ai_e  triggers a floating-point
division-by-zero exception with the input -1.842761151977744. The exception
can be trapped by using “feenableexcept”, but it will disappear if you
slightly disturb the input, say, to -1.84276115198. By digging into the issue,
I have observed that in the airy_mod_phase function that airy_Ai invokes, the
variable result_m is divided whereas it has vanished following a non-trivial
computation (with loops, etc., in function cheb_eval_mode_e). Please check the
code airy_divbyzero.c below.



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File Attachments:


-------------------------------------------------------
Date: Tue 07 Nov 2017 03:32:37 PM UTC  Name: airy_divbyzero.c  Size: 678B  
By: psa

<http://savannah.gnu.org/bugs/download.php?file_id=42343>

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