  The step-by-step chromaticity compensation method for chromatic sextupole
optimization and dynamic aperture increase was proposed by E. Levichev and P.
Piminov (E. Levichev and P. Piminov, 2006 [1]). Although this method can be
used to enlarge the dynamic aperture of storage ring, it has some drawbacks. In
this paper, we combined this method with evolutionary computation algorithms,
and proposed an improved version of this method. In the improved method, the
drawbacks are avoided, and thus better optimization results can be obtained.
