Gordon Royle on Mon, 05 Jul 2004 13:01:12 +0200


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Polynomial Roots - how to interpret realprecision?


I want to use "polroots" to calculate the roots of a large number of *integer* polynomials.

The documentation indicates that the precision is kept in the variable realprecision.... and then it says

".. it is guaranteed to converge and to give the roots to the required precision"


Now, does this mean that the roots that are output are guaranteed correct to that number of places? From my (admittedly limited) understanding of the sensitivity of roots of polynomials, I was under the impression that this would require some intermediate calculations to be performed to a greater precision ... is this so?

Thanks

Gordon