  The concept of prefactors is considered in order to decrease the complexity
of the Guruswami-Sudan interpolation step for generalized Reed-Solomon codes.
It is shown that the well-known re-encoding projection due to Koetter et al.
leads to one type of such prefactors. The new type of Sierpinski prefactors is
introduced. The latter are based on the fact that many binomial coefficients in
the Hasse derivative associated with the Guruswami-Sudan interpolation step are
zero modulo the base field characteristic. It is shown that both types of
prefactors can be combined and how arbitrary prefactors can be used to derive a
reduced Guruswami-Sudan interpolation step.
