Function: polroots
Section: polynomials
C-Name: roots
Prototype: Gp
Help: polroots(T): complex roots of the polynomial T using
Schonhage's method, as modified by Gourdon.
Doc: complex roots of the polynomial
$T$, given as a column vector where each root is repeated according to
its multiplicity. The precision is given as for transcendental functions: in
GP it is kept in the variable \kbd{realprecision} and is transparent to the
user, but it must be explicitly given as a second argument in library mode.
The algorithm used is a modification of Sch\"onhage\sidx{Sch\"onage}'s
root-finding algorithm, due to and originally implemented by Gourdon.
It is guaranteed to converge; if furthermore $T$ has rational coefficients,
roots are guaranteed to the required relative accuracy.