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Re: [Bug-gsl] problem in cubic solver
From: |
Brian Gough |
Subject: |
Re: [Bug-gsl] problem in cubic solver |
Date: |
Wed, 29 Apr 2009 12:22:04 +0200 |
User-agent: |
Wanderlust/2.14.0 (Africa) Emacs/22.1 Mule/5.0 (SAKAKI) |
At Tue, 28 Apr 2009 17:11:31 +0200,
Lorenzo Moneta wrote:
> I have found a problem with solver for cubic equation (both complex
> and real one)
> In some particular case a NaN is returned, as shown in the attached
> text example.
> The problem is observed mainly on 64 bit architectures (for example
> Linux 64-bit with gcc 4.3) and not on 32 bit architectures.
>
> This is due to a problem in a sqrt. A patch is attached fixing the
> problem for the complex routine (gsl_poly_complex_solve_cubic ).
> A similar patch can be probably done also for the real routine
>
> This patch fails the current test for polynomial in gsl, however in
> my opinion, this is acceptable, because the test condition is too
> strict. With a slight change of the test coefficient, you will have a
> similar failure also with the current version.
Thanks for the bug report and patch, I will look at that.
--
Brian Gough