Strum Algorithm And Number of Distinct Roots

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Strum Algorithm And Number of Distinct Roots

Ahmed Essam
Hi all,

I have been playing with CGAL's polynomial utilities and I have a question.
As far as I understand Strum's algorithm, it should calculate the exact number of distinct real roots. There is a polynomial however, where it overestimates the number of real roots, and when I calculate the roots, it repeated one of them, even though it wasn't a repeated root. Is this normal behavior?

Thanks,
Ahmed Essam
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Re: Strum Algorithm And Number of Distinct Roots

Sebastien Loriot (GeometryFactory)
Is the root repeat a non degree 1 root?
Do you have an example showing the problem?

Best,

Sebastien.

On 3/5/20 1:08 PM, Ahmed Essam wrote:

> Hi all,
>
> I have been playing with CGAL's polynomial utilities and I have a question.
> As far as I understand Strum's algorithm, it should calculate the exact
> number of distinct real roots. There is a polynomial however, where it
> overestimates the number of real roots, and when I calculate the roots,
> it repeated one of them, even though it wasn't a repeated root. Is this
> normal behavior?
>
> Thanks,
> Ahmed Essam

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Re: Strum Algorithm And Number of Distinct Roots

Ahmed Essam
It was the case with the bezier bug, I depended on visual representation. The output of the algorithm is correct, there were 3 different roots all very close to each other, that they were 'cout'ed as the same string. Mistake is on my part.

Thanks,
Ahmed Essam.

On Wed, Mar 11, 2020, 9:45 AM Sebastien Loriot (GeometryFactory) <[hidden email]> wrote:
Is the root repeat a non degree 1 root?
Do you have an example showing the problem?

Best,

Sebastien.

On 3/5/20 1:08 PM, Ahmed Essam wrote:
> Hi all,
>
> I have been playing with CGAL's polynomial utilities and I have a question.
> As far as I understand Strum's algorithm, it should calculate the exact
> number of distinct real roots. There is a polynomial however, where it
> overestimates the number of real roots, and when I calculate the roots,
> it repeated one of them, even though it wasn't a repeated root. Is this
> normal behavior?
>
> Thanks,
> Ahmed Essam

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