[Bug-gsl] [bug #39466] errors in gsl_sf_coupling_6j_e and gsl_sf_coupling_9j_e

[Patrick Alken]

URL:
  <http://savannah.gnu.org/bugs/?39466>

                 Summary: errors in gsl_sf_coupling_6j_e and
gsl_sf_coupling_9j_e
                 Project: GNU Scientific Library
            Submitted by: psa
            Submitted on: Thu 11 Jul 2013 05:49:47 PM GMT
                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 coupling of three spins requires the total sum to be integer.  This is 
not checked on gsl_sf_coupling_6j_e or gsl_sf_coupling_9j_e.

We discovered it when trying to evaluate the 9j symbol:

(1/2 1/2 1/2)
(1/2 1/2 1/2)
( 0   0   0 )

and got a non-zero result.  We believe that the recursive calculations of 
6j should have given the zero, but found also that lacking similar checks.

The attached patch also include some test cases.  The 6js have been 
cross-checked with Mathematica.

Best regards,
Håkan Johansson



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File Attachments:


-------------------------------------------------------
Date: Thu 11 Jul 2013 05:49:47 PM GMT  Name: coupling_6_9_halfint_check.diff 
Size: 3kB   By: psa

<http://savannah.gnu.org/bugs/download.php?file_id=28544>

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