bugGNU Scientific Library - Bugs: bug #30885, nans from...

 
 

You are not allowed to post comments on this tracker with your current authentification level.

bug #30885: nans from gsl_sf_coulomb_wave_FG_e(1.2693881947287221e-07, 0.0, lam_F=37, lam_G=36)

Submitted by:  Brian Gough <bjg>
Submitted on:  Fri 27 Aug 2010 10:48:31 AM UTC  
 
Category: Runtime errorSeverity: 3 - Normal
Operating System: Status: Confirmed
Assigned to: NoneOpen/Closed: Open
Release: 1.14

Fri 27 Aug 2010 10:48:31 AM UTC, original submission:

From: "Alexey A. Illarionov" <alexey.illarionov@gmail.com>
To: -unavailable-
Subject: [Bug-gsl] bug in gsl_sf_coulomb_wave_FG_e (gsl 1.14 compiled with \
gcc 4.5.0)
Date: Wed, 25 Aug 2010 23:41:14 -0400

[1 <text/plain; UTF-8 (7bit)>]
Hi guys,

It seems that I find a bug in gsl_sf_coulomb_wave_FG_e. For large values
of lambda and small values of x, with eta = 0 it produces nan values
without raising of the flag.

Here the sample cases (see attachment with example)
gsl_sf_coulomb_wave_FG_e(0.,1.2693881947287221e-07, 37, 1, ...)
gsl_sf_coulomb_wave_FG_e(0.,5.911135077240691e-07, 39, 1, ...)
gsl_sf_coulomb_wave_FG_e(0.,6.118185507743884e-07, 40, 1, ...)
and lots of others.

It seems that the origin of the problem is at
coulomb_F_recur
function (call at coulomb.c:970), that return garbage-like big numbers
but the error flag is not raised.

Here since we are interested only in unnormalized values we can makes a
workaround like checking if values greater than some number, renormalize
them to 1 for some value. But if this function is used elsewhere with
the need of normalized values, this workaround will produce problems there.

Unfortunately I don't have time right now to dig in more, I'll try look
at it at the weekend if the issue is not solved by that date.

P.S. I'm not sure, but for me at this values of arguments (x <<
x_{turning_point}) using series approximation directly is more adequate
(if we do not consider G and Gp which I'm not sure how to deal).

Brian Gough <bjg>
Project Administrator

 

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by bjg (Submitted the item)
  •  

    Please enter the title of George Orwell's famous dystopian book (it's a date):

     

     

    No Changes Have Been Made to This Item

    Back to the top


    Powered by Savane 3.1-cleanup