The option ResidualStrategy determines which strategy is used to compute the residuals, which is the main step in the computation of the Chern and Segre classes. When choosing the default Symbolic, Gröbner basis methods will be used. The computations can also be done numerically using the regenerative cascade implemented in Bertini. This is done by choosing the option Bertini and provided Bertini is installed and configured. Using Bertini will usually result in a considerable speed-up.