On the topic of cubics, have you tried translating CERNLIB's rrteq3
into C for root? I have found it to give better results in general
than GSL's cubic routine, and thus it might be worth adding a
translation of the CERNLIB code to GSL.
My attempt at this translation is given at line 517 of
http://o2scl.svn.sourceforge.net/viewvc/o2scl/trunk/src/other/poly.cpp?revision=35&view=markup
Take care,
Andrew
On Tue, Apr 28, 2009 at 11:11 AM, Lorenzo Moneta <Lorenzo.Moneta@cern.ch
> wrote:
Hello,
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.
Best Regards
Lorenzo Moneta
ROOT project (http://root.cern.ch )
CERN
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