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Re: gsl_sf_coupling_3j
- From: Brian Gough <bjg at network-theory dot co dot uk>
- To: Filip Floegel <floegel at itp dot uni-hannover dot de>
- Cc: gsl-discuss at sources dot redhat dot com
- Date: Thu, 3 Oct 2002 21:19:03 +0100 (BST)
- Subject: Re: gsl_sf_coupling_3j
- References: <20021002154552.GA19031@itp.uni-hannover.de>
Filip Floegel writes:
> hello gsl community,
> gsl_sf_coupling_3j doesn't work properly for large angular mementa
> like j1=j2=j3=40 m1=m2=m3=0 !!!
> gsl_sf_coupling_3j_e(80,80,80,0,0,0,&result)
> which correspond to j1=j2=j3=40 m1=m2=m3=0
> gives me:
> result.val = 0.0625 result.err = 0.172766
> mathematica gives me:
> N[ThreeJSymbol[{40,0},{40,0},{40,0}]] = 0.0149685
> my guess is that gamma.c which is used for calculating fractional
> numbers probably diverges for large integers.
Thanks for the bug report.
If you can take a look at the source maybe a different expansion can
be used for large values to improve the accuracy?
Brian