[Bug-gsl] Error in coulomb.c

[Alexey A. Illarionov]

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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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