Re: [Bug-gsl] Error in coulomb.c

[Patrick Alken]

Hi, thanks for the report. Do you have an example of calling the 
gsl_sf_coulomb_wave_FG_e function with input arguments that lead to the 
wrong output? This would be useful in making test cases for this issue.

Patrick

On 06/18/2013 11:58 PM, Alexey A. Illarionov wrote:
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> Accidentally found a bug in specfun/coulomb.c . Trivial error in
> solution of quadratic equation. None of the current test cases are
> influenced by this bug since the value of C (actually N) determines
> only the condition of applicability of "continued fraction+recursion"
> algorithm.
>
> === modified file 'specfunc/coulomb.c'
> - --- specfunc/coulomb.c        2007-07-02 18:34:24 +0000
> +++ specfunc/coulomb.c  2012-10-26 04:27:18 +0000
> @@ -1121,7 +1121,7 @@
>        *           we must go at least as low as lam_G
>        */
>       const double SMALL = GSL_SQRT_DBL_EPSILON;
> - -    const double C = sqrt(1.0 + 4.0*x*(x-2.0*eta));
> +    const double C = 0.5 * sqrt(1.0 + 4.0*x*(x-2.0*eta));
>       const int N = ceil(lam_F - C + 0.5);
>       const double lam_0   = lam_F - GSL_MAX(N, 0);
>       const double lam_min = GSL_MIN(lam_0, lam_G);
>
> - -- 
> С уважением, Алексей Александрович Илларионов.
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