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Re: [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finit
From: |
Alexey A. Illarionov |
Subject: |
Re: [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess |
Date: |
Sun, 06 Oct 2013 00:51:57 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:19.0) Gecko/20100101 Firefox/19.0 SeaMonkey/2.16.2 |
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Hi,
Just curious, how is this form preferable than the other?
In my opinions none of the forms avoid the loss of precision when f
and f_new are close.
Brian Gladman wrote:
> Update of bug #39713 (project gsl):
>
> Status: Ready For Test => Fixed
>
> _______________________________________________________
>
> Follow-up Comment #17:
>
> Thanks for testing the fix on Linux, which allows me to mark it as
> fixed.
>
> The form df_new = df * (1 - f_new / f) is better than the earlier
> expression because it avoids the severe loss of precision when
> (x_new - x) is used in the demominator of the expression for df_new
> (this was the primary cause of the problems you experienced).
>
> In fact I have just made a further change to:
>
> df_new = df * ((f - f_new) / f);
>
> which avoids the possible loss of precision in using (1 - f_new /
> f).
>
>
> _______________________________________________________
>
> Reply to this item at:
>
> <http://savannah.gnu.org/bugs/?39713>
>
> _______________________________________________ Message sent via/by
> Savannah http://savannah.gnu.org/
>
>
- --
С уважением, Алексей Александрович Илларионов.
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- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, (continued)
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/02
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Rhys Ulerich, 2013/10/02
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/02
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/03
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/03
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Max, 2013/10/05
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Max, 2013/10/05
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/05
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Max, 2013/10/05
- [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/05
- Re: [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess,
Alexey A. Illarionov <=
- Re: [Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess, Brian Gladman, 2013/10/06