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Re: [Bug-gsl] redundant checks in triangle_selection_fails
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From: |
Alexey A. Illarionov |
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Subject: |
Re: [Bug-gsl] redundant checks in triangle_selection_fails |
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Date: |
Thu, 11 Jul 2013 13:38:14 -0400 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20100101 Firefox/19.0 SeaMonkey/2.16.2 |
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Hi, the function should be
static
int
triangle_selection_fails(int two_ja, int two_jb, int two_jc)
{
return ((two_jb < abs(two_ja - two_jc)) || (two_jb > two_ja +
two_jc)) || GSL_IS_ODD(two_jb + two_ja + two_jc);
}
This should also solve the problem of 6j and 9j.
Btw, the the algorithm of evaluation of 3j, 6j, 9j in GSL is the worst
possible. It just follows the Racah formula and does not use any
symmetry properties. See [Tuzun et all, Comp Phys Comm, 1998] for 3j,
6j algorithms.
Håkan Johansson wrote:
>
> In bzr trunk, the function triangle_selection_fails in
> specfunc/coupling.c has grown a number of redundant tests since
> v1.15. It is enough to check the triangle condition for one spin vs
> the other two. (See attached test program.) Perhaps put a comment
> to keep the function lean?
>
> Cheers, Håkan Johansson
- --
С уважением, Алексей Александрович Илларионов.
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