WP 34S Solver

[Marcio]

(05-28-2015 03:52 PM)Pascal Wrote:  

(05-28-2015 04:27 AM)Marcio Wrote:  Try to find the roots for x^2-5*x+6 (2 and 3) and use 1 and 1.5 as initial guesses. You'll get an error. Oddly enough, if your guesses are greater than 3 (but not much!), the calc will return 3.

Hi Marcio,
That was a bug in the Solver algorithm that I mentioned some weeks ago. Pauli has updated the corresponding file, so your example should work with the next firmware version.
Pascal

Funny we used the same equation exactly. Anyways, in this POST from 2012, Pauli says the following:

Quote:The solver should stay within the two estimate IF they produce function evaluations of opposite signs. Otherwise, they are just used as a guide and it is free to wander outside.
The solver uses a quadratic interpolation step but this is guarded against going to far or encountering problems with either a secant or bisection step instead.
I have code to use Ridder's method after a bisection instead of the quadratic interpolation. This is supposed to be better but I never noticed enough of an improvement to justify its inclusion and so it isn't included in the build.
- Pauli

Meaning the method is not restricted to regula falsi. I don't know if they were able to take a look at this bug though.