Re: fzero initial bracketing [WAS: bug #31070]

[c.]

On 21 Sep 2010, at 13:05, Jaroslav Hajek wrote:

> x0 = initial guess;
> n = 1;
> fx0 = fun (x0);
>
> while (1)
>  for k = 1:2:n
>    d = k*2^(k-n);
>    x1 = x0 + d;
>    if (sign (fun (x1)) * sign (fx0) <= 0)
>      break;
>    endif
>    x1 = x0 - d;
>    if (sign (fun (x1)) * sign (fx0) <= 0)
>      break;
>    endif
>  endfor
>  n++;
> endwhile

BTW that is the same approach I had in mind except for imposing a  
lower and upper limit to d: tolx*abs(x0) < d < abs (x0).
I agree that it is unpractical to search for the bracketing over the  
whole real axis, but a finite number of attempts
might still make sense.

c.