🚀 go-pugleaf

In article <1992Aug25.161234.13275@magnus.acs.ohio-state.edu>
 kiyer@magnus.acs.ohio-state.edu (Karthik A Iyer) writes:

>Dear fellow nettors,
>	            I am looking for a routine(s) or a place where I can find 
>them (FTP sites, etc) to solve quartic and cubic eqations. I realize that 
>analytic solutions exist, but my problem is that the coefficients of the 
>powers vary by as much as 10-15 orders of magnitude. So, a small error is
>solving the for the cubic's root leads to large errors when that root is
>used to solve for the four roots of the quartic. Any help or leads  would be
>appreciated. I would prefer to get my hands on a FORTRAN double precision 
>routine. Thanks in advance,...


The first of the Graphics Gems books contains routines for quick solution for
the roots of the third and fourth order polynomials.

I don't know if they are accurate when presented with extreme coefficients.
They are coded in C.

The code is by Jochen Schwarze, and the explanation is on page 404 of the text.

"Graphics Gems", ed. Andrew S. Glassner, Academic Press,Inc., Boston, 1990
ISBN 0-12-286165-5
T385.G697

The code can also be found at a few sites in the net.

peter