Abstract
We propose a simple procedure for setting the efficient starting values of the Durand-Kerner iteration, which finds all zeros α_i(i = 1, ・・・, n) of a polynomial of degree n simultaneously. In our new procedure, the starting values are located on the circle centered at β with radius γ_<gm>where β = 1/nΣ^^n__<i=1>α_i, and γ_<gm> is the geometric mean of the deviations |α_i - β|. The computational cost for this procedure is extremely cheap compared with that for Aberth's procedure. Moreover, the various numerical examples show that our new method reduces the number of iterations tremendously over any other ones, particularly when some of the deviations |α_i - β| are large.
